Try using installable Preferences library

Two variants are redundant

.github/workflows/build.yml

@@ -15,11 +15,27 @@ jobs:
     - name: Install Arduino CLI
       run: curl -fsSL https://raw.githubusercontent.com/arduino/arduino-cli/master/install.sh | BINDIR=/usr/local/bin sh
     - name: Build firmware
+      env:
+        ARDUINO_SKETCH_ALWAYS_EXPORT_BINARIES: 1
       run: make
-    - name: Build firmware without Wi-Fi
+    - name: Upload binaries
+      uses: actions/upload-artifact@v4
+      with:
+        name: firmware-binary
+        path: flix/build
+    - name: Build firmware for ESP32-S3
+      run: make BOARD=esp32:esp32:esp32s3
+    - name: Build firmware with WiFi disabled
       run: sed -i 's/^#define WIFI_ENABLED 1$/#define WIFI_ENABLED 0/' flix/flix.ino && make
     - name: Check c_cpp_properties.json
       run: tools/check_c_cpp_properties.py
+    - name: Build for Black Pill F411CE (STM32)
+      run: |
+        arduino-cli config set board_manager.additional_urls https://github.com/stm32duino/BoardManagerFiles/raw/main/package_stmicroelectronics_index.json
+        arduino-cli core install STMicroelectronics:stm32
+        arduino-cli board listall STMicroelectronics:stm32
+        arduino-cli lib install "Preferences"
+        make BOARD=STMicroelectronics:stm32:GenF4:pnum=BLACKPILL_F411CE
 
   build_macos:
     runs-on: macos-latest
@@ -46,15 +62,25 @@ jobs:
       run: python3 tools/check_c_cpp_properties.py
 
   build_simulator:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
+    container:
+      image: ubuntu:20.04
     steps:
+    - name: Install dependencies
+      run: |
+        apt-get update
+        DEBIAN_FRONTEND=noninteractive apt-get install -y curl wget build-essential cmake g++ pkg-config gnupg2 lsb-release sudo
     - name: Install Arduino CLI
       uses: arduino/setup-arduino-cli@v1.1.1
     - uses: actions/checkout@v4
     - name: Install Gazebo
-      run: curl -sSL http://get.gazebosim.org | sh
+      run: |
+        sudo sh -c 'echo "deb http://packages.osrfoundation.org/gazebo/ubuntu-stable `lsb_release -cs` main" > /etc/apt/sources.list.d/gazebo-stable.list'
+        wget https://packages.osrfoundation.org/gazebo.key -O - | sudo apt-key add -
+        sudo apt-get update
+        sudo apt-get install -y gazebo11 libgazebo11-dev
     - name: Install SDL2
-      run: sudo apt-get install libsdl2-dev
+      run: sudo apt-get install -y libsdl2-dev
     - name: Build simulator
       run: make build_simulator
     - uses: actions/upload-artifact@v4

.github/workflows/tools.yml

@@ -19,6 +19,21 @@ jobs:
         echo -e "t,x,y,z\n0,1,2,3\n1,4,5,6" > log.csv
         ./csv_to_ulog log.csv
         test $(stat -c %s log.ulg) -eq 196
+  pyflix:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+    - name: Install Python build tools
+      run: pip install build
+    - name: Build pyflix
+      run: python3 -m build tools
+    - name: Upload artifacts
+      uses: actions/upload-artifact@v4
+      with:
+        name: pyflix
+        path: |
+          tools/dist/pyflix-*.tar.gz
+          tools/dist/pyflix-*.whl
   python_tools:
     runs-on: ubuntu-latest
     steps:

.gitignore

@@ -2,6 +2,8 @@
 *.elf
 build/
 tools/log/
+tools/dist/
+*.egg-info/
 .dependencies
 .vscode/*
 !.vscode/settings.json

.markdownlint.json

@@ -34,6 +34,7 @@
 			"MPU-6050",
 			"MPU-9250",
 			"GY-91",
+			"GY-521",
 			"ICM-20948",
 			"Linux",
 			"Windows",

.vscode/c_cpp_properties.json

@@ -5,18 +5,20 @@
 			"includePath": [
 				"${workspaceFolder}/flix",
 				"${workspaceFolder}/gazebo",
-				"~/.arduino15/packages/esp32/hardware/esp32/3.1.0/cores/esp32",
-				"~/.arduino15/packages/esp32/hardware/esp32/3.1.0/libraries/**",
-				"~/.arduino15/packages/esp32/hardware/esp32/3.1.0/variants/d1_mini32",
-				"~/.arduino15/packages/esp32/tools/esp32-arduino-libs/idf-release_v5.3-083aad99-v2/esp32/**",
-				"~/.arduino15/packages/esp32/tools/esp32-arduino-libs/idf-release_v5.3-083aad99-v2/esp32/dio_qspi/include",
+				"${workspaceFolder}/tools/**",
+				"~/.arduino15/packages/esp32/hardware/esp32/3.2.0/cores/esp32",
+				"~/.arduino15/packages/esp32/hardware/esp32/3.2.0/libraries/**",
+				"~/.arduino15/packages/esp32/hardware/esp32/3.2.0/variants/d1_mini32",
+				"~/.arduino15/packages/esp32/tools/esp32-arduino-libs/idf-release_v5.4-2f7dcd86-v1/esp32/**",
+				"~/.arduino15/packages/esp32/tools/esp32-arduino-libs/idf-release_v5.4-2f7dcd86-v1/esp32/dio_qspi/include",
 				"~/Arduino/libraries/**",
-				"/usr/include/**"
+				"/usr/include/gazebo-11/",
+				"/usr/include/ignition/math6/"
 			],
 			"forcedInclude": [
 				"${workspaceFolder}/.vscode/intellisense.h",
-				"~/.arduino15/packages/esp32/hardware/esp32/3.1.0/cores/esp32/Arduino.h",
-				"~/.arduino15/packages/esp32/hardware/esp32/3.1.0/variants/d1_mini32/pins_arduino.h",
+				"~/.arduino15/packages/esp32/hardware/esp32/3.2.0/cores/esp32/Arduino.h",
+				"~/.arduino15/packages/esp32/hardware/esp32/3.2.0/variants/d1_mini32/pins_arduino.h",
 				"${workspaceFolder}/flix/cli.ino",
 				"${workspaceFolder}/flix/control.ino",
 				"${workspaceFolder}/flix/estimate.ino",
@@ -31,7 +33,7 @@
 				"${workspaceFolder}/flix/wifi.ino",
 				"${workspaceFolder}/flix/parameters.ino"
 			],
-			"compilerPath": "~/.arduino15/packages/esp32/tools/esp-x32/2405/bin/xtensa-esp32-elf-g++",
+			"compilerPath": "~/.arduino15/packages/esp32/tools/esp-x32/2411/bin/xtensa-esp32-elf-g++",
 			"cStandard": "c11",
 			"cppStandard": "c++17",
 			"defines": [
@@ -51,19 +53,19 @@
 			"name": "Mac",
 			"includePath": [
 				"${workspaceFolder}/flix",
-				"${workspaceFolder}/gazebo",
-				"~/Library/Arduino15/packages/esp32/hardware/esp32/3.1.0/cores/esp32",
-				"~/Library/Arduino15/packages/esp32/hardware/esp32/3.1.0/libraries/**",
-				"~/Library/Arduino15/packages/esp32/hardware/esp32/3.1.0/variants/d1_mini32",
-				"~/Library/Arduino15/packages/esp32/tools/esp32-arduino-libs/idf-release_v5.3-083aad99-v2/esp32/include/**",
-				"~/Library/Arduino15/packages/esp32/tools/esp32-arduino-libs/idf-release_v5.3-083aad99-v2/esp32/dio_qspi/include",
+				"~/Library/Arduino15/packages/esp32/hardware/esp32/3.2.0/cores/esp32",
+				"~/Library/Arduino15/packages/esp32/hardware/esp32/3.2.0/libraries/**",
+				"~/Library/Arduino15/packages/esp32/hardware/esp32/3.2.0/variants/d1_mini32",
+				"~/Library/Arduino15/packages/esp32/tools/esp32-arduino-libs/idf-release_v5.4-2f7dcd86-v1/esp32/include/**",
+				"~/Library/Arduino15/packages/esp32/tools/esp32-arduino-libs/idf-release_v5.4-2f7dcd86-v1/esp32/dio_qspi/include",
 				"~/Documents/Arduino/libraries/**",
-				"/opt/homebrew/include/**"
+				"/opt/homebrew/include/gazebo-11/",
+				"/opt/homebrew/include/ignition/math6/"
 			],
 			"forcedInclude": [
 				"${workspaceFolder}/.vscode/intellisense.h",
-				"~/Library/Arduino15/packages/esp32/hardware/esp32/3.1.0/cores/esp32/Arduino.h",
-				"~/Library/Arduino15/packages/esp32/hardware/esp32/3.1.0/variants/d1_mini32/pins_arduino.h",
+				"~/Library/Arduino15/packages/esp32/hardware/esp32/3.2.0/cores/esp32/Arduino.h",
+				"~/Library/Arduino15/packages/esp32/hardware/esp32/3.2.0/variants/d1_mini32/pins_arduino.h",
 				"${workspaceFolder}/flix/flix.ino",
 				"${workspaceFolder}/flix/cli.ino",
 				"${workspaceFolder}/flix/control.ino",
@@ -78,7 +80,7 @@
 				"${workspaceFolder}/flix/wifi.ino",
 				"${workspaceFolder}/flix/parameters.ino"
 			],
-			"compilerPath": "~/Library/Arduino15/packages/esp32/tools/esp-x32/2405/bin/xtensa-esp32-elf-g++",
+			"compilerPath": "~/Library/Arduino15/packages/esp32/tools/esp-x32/2411/bin/xtensa-esp32-elf-g++",
 			"cStandard": "c11",
 			"cppStandard": "c++17",
 			"defines": [
@@ -100,17 +102,18 @@
 			"includePath": [
 				"${workspaceFolder}/flix",
 				"${workspaceFolder}/gazebo",
-				"~/AppData/Local/Arduino15/packages/esp32/hardware/esp32/3.1.0/cores/esp32",
-				"~/AppData/Local/Arduino15/packages/esp32/hardware/esp32/3.1.0/libraries/**",
-				"~/AppData/Local/Arduino15/packages/esp32/hardware/esp32/3.1.0/variants/d1_mini32",
-				"~/AppData/Local/Arduino15/packages/esp32/tools/esp32-arduino-libs/idf-release_v5.3-083aad99-v2/esp32/**",
-				"~/AppData/Local/Arduino15/packages/esp32/tools/esp32-arduino-libs/idf-release_v5.3-083aad99-v2/esp32/dio_qspi/include",
+				"${workspaceFolder}/tools/**",
+				"~/AppData/Local/Arduino15/packages/esp32/hardware/esp32/3.2.0/cores/esp32",
+				"~/AppData/Local/Arduino15/packages/esp32/hardware/esp32/3.2.0/libraries/**",
+				"~/AppData/Local/Arduino15/packages/esp32/hardware/esp32/3.2.0/variants/d1_mini32",
+				"~/AppData/Local/Arduino15/packages/esp32/tools/esp32-arduino-libs/idf-release_v5.4-2f7dcd86-v1/esp32/**",
+				"~/AppData/Local/Arduino15/packages/esp32/tools/esp32-arduino-libs/idf-release_v5.4-2f7dcd86-v1/esp32/dio_qspi/include",
 				"~/Documents/Arduino/libraries/**"
 			],
 			"forcedInclude": [
 				"${workspaceFolder}/.vscode/intellisense.h",
-				"~/AppData/Local/Arduino15/packages/esp32/hardware/esp32/3.1.0/cores/esp32/Arduino.h",
-				"~/AppData/Local/Arduino15/packages/esp32/hardware/esp32/3.1.0/variants/d1_mini32/pins_arduino.h",
+				"~/AppData/Local/Arduino15/packages/esp32/hardware/esp32/3.2.0/cores/esp32/Arduino.h",
+				"~/AppData/Local/Arduino15/packages/esp32/hardware/esp32/3.2.0/variants/d1_mini32/pins_arduino.h",
 				"${workspaceFolder}/flix/cli.ino",
 				"${workspaceFolder}/flix/control.ino",
 				"${workspaceFolder}/flix/estimate.ino",
@@ -125,7 +128,7 @@
 				"${workspaceFolder}/flix/wifi.ino",
 				"${workspaceFolder}/flix/parameters.ino"
 			],
-			"compilerPath": "~/AppData/Local/Arduino15/packages/esp32/tools/esp-x32/2405/bin/xtensa-esp32-elf-g++.exe",
+			"compilerPath": "~/AppData/Local/Arduino15/packages/esp32/tools/esp-x32/2411/bin/xtensa-esp32-elf-g++.exe",
 			"cStandard": "c11",
 			"cppStandard": "c++17",
 			"defines": [

.vscode/extensions.json

@@ -2,7 +2,6 @@
 	// See https://go.microsoft.com/fwlink/?LinkId=827846 to learn about workspace recommendations.
 	"recommendations": [
 		"ms-vscode.cpptools",
-		"twxs.cmake",
 		"ms-vscode.cmake-tools",
 		"ms-python.python"
 	],

.vscode/settings.json

@@ -1,5 +1,6 @@
 {
 	"C_Cpp.intelliSenseEngineFallback": "enabled",
+	"C_Cpp.errorSquiggles": "disabled",
 	"files.associations": {
 		"*.sdf": "xml",
 		"*.ino": "cpp",

Makefile

@@ -13,10 +13,10 @@ monitor:
 
 dependencies .dependencies:
 	arduino-cli core update-index --config-file arduino-cli.yaml
-	arduino-cli core install esp32:esp32@3.1.0 --config-file arduino-cli.yaml
+	arduino-cli core install esp32:esp32@3.2.0 --config-file arduino-cli.yaml
 	arduino-cli lib update-index
 	arduino-cli lib install "FlixPeriph"
-	arduino-cli lib install "MAVLink"@2.0.12
+	arduino-cli lib install "MAVLink"@2.0.16
 	touch .dependencies
 
 gazebo/build cmake: gazebo/CMakeLists.txt

README.md

@@ -15,49 +15,60 @@
 
 ## Features
 
-* Simple and clean Arduino based source code.
-* Acro and Stabilized flight using remote control.
-* Precise simulation using Gazebo.
-* [In-RAM logging](docs/log.md).
-* Command line interface through USB port.
-* Wi-Fi support.
-* MAVLink support.
-* Control using mobile phone (with QGroundControl app).
-* Completely 3D-printed frame.
-* Textbook for students on writing a flight controller ([in development](https://quadcopter.dev)).
-* *Position control and autonomous flights using external camera¹*.
-* [Building and running instructions](docs/build.md).
+* Dedicated for education and research.
+* Made from general-purpose components.
+* Simple and clean source code in Arduino (<2k lines firmware).
+* Control using USB gamepad, remote control or smartphone.
+* Wi-Fi and MAVLink support.
+* Wireless command line interface and analyzing.
+* Precise simulation with Gazebo.
+* Python library.
+* Textbook on flight control theory and practice ([in development](https://quadcopter.dev)).
+* *Position control (using external camera) and autonomous flights¹*.
 
 *¹ — planned.*
 
 ## It actually flies
 
-See detailed demo video (for version 0): https://youtu.be/8GzzIQ3C6DQ.
+See detailed demo video: https://youtu.be/hT46CZ1CgC4.
+
+<a href="https://youtu.be/hT46CZ1CgC4"><img width=500 src="https://i3.ytimg.com/vi/hT46CZ1CgC4/maxresdefault.jpg"></a>
+
+Version 0 demo video: https://youtu.be/8GzzIQ3C6DQ.
 
 <a href="https://youtu.be/8GzzIQ3C6DQ"><img width=500 src="https://i3.ytimg.com/vi/8GzzIQ3C6DQ/maxresdefault.jpg"></a>
 
-Version 1 test flight: https://t.me/opensourcequadcopter/42.
+Usage in education (RoboCamp): https://youtu.be/Wd3yaorjTx0.
 
-<a href="https://t.me/opensourcequadcopter/42"><img width=500 src="docs/img/flight-video.jpg"></a>
+<a href="https://youtu.be/Wd3yaorjTx0"><img width=500 src="https://i3.ytimg.com/vi/Wd3yaorjTx0/sddefault.jpg"></a>
 
-See the [user builds gallery](docs/user.md).
+See the [user builds gallery](docs/user.md):
 
-<img src="docs/img/user/user.jpg" width=400>
+<a href="docs/user.md"><img src="docs/img/user/user.jpg" width=500></a>
 
 ## Simulation
 
 The simulator is implemented using Gazebo and runs the original Arduino code:
 
-<img src="docs/img/simulator.png" width=500 alt="Flix simulator">
+<img src="docs/img/simulator1.png" width=500 alt="Flix simulator">
 
-See [instructions on running the simulation](docs/build.md).
+## Articles
 
-## Components (version 1)
+* [Assembly instructions](docs/assembly.md).
+* [Usage: build, setup and flight](docs/usage.md).
+* [Troubleshooting](docs/troubleshooting.md).
+* [Firmware architecture overview](docs/firmware.md).
+* [Python library tutorial](tools/pyflix/README.md).
+* [Log analysis](docs/log.md).
+* [User builds gallery](docs/user.md).
+
+## Components
 
 |Type|Part|Image|Quantity|
 |-|-|:-:|:-:|
 |Microcontroller board|ESP32 Mini|<img src="docs/img/esp32.jpg" width=100>|1|
-|IMU (and barometer²) board|GY‑91 (or other MPU‑9250/MPU‑6500 board), ICM‑20948³|<img src="docs/img/gy-91.jpg" width=90 align=center><img src="docs/img/icm-20948.jpg" width=100>|1|
+|IMU (and barometer²) board|GY‑91, MPU-9265 (or other MPU‑9250/MPU‑6500 board)<br>ICM20948V2 (ICM‑20948)³<br>GY-521 (MPU-6050)³⁻¹|<img src="docs/img/gy-91.jpg" width=90 align=center><br><img src="docs/img/icm-20948.jpg" width=100><br><img src="docs/img/gy-521.jpg" width=100>|1|
+|<span style="background:yellow">Buck-boost converter</span> (recommended)|To be determined, output 5V or 3.3V, see [user-contributed schematics](https://miro.com/app/board/uXjVN-dTjoo=/?moveToWidget=3458764612179508274&cot=14)|<img src="docs/img/buck-boost.jpg" width=100>|1|
 |Motor|8520 3.7V brushed motor (shaft 0.8mm).<br>Motor with exact 3.7V voltage is needed, not ranged working voltage (3.7V — 6V).|<img src="docs/img/motor.jpeg" width=100>|4|
 |Propeller|Hubsan 55 mm|<img src="docs/img/prop.jpg" width=100>|4|
 |MOSFET (transistor)|100N03A or [analog](https://t.me/opensourcequadcopter/33)|<img src="docs/img/100n03a.jpg" width=100>|4|
@@ -67,18 +78,19 @@ See [instructions on running the simulation](docs/build.md).
 |Li-Po Battery charger|Any|<img src="docs/img/charger.jpg" width=100>|1|
 |Screws for IMU board mounting|M3x5|<img src="docs/img/screw-m3.jpg" width=100>|2|
 |Screws for frame assembly|M1.4x5|<img src="docs/img/screw-m1.4.jpg" height=30 align=center>|4|
-|Frame bottom part|3D printed⁴:<br>[`flix-frame-1.1.stl`](docs/assets/flix-frame-1.1.stl) [`flix-frame-1.1.step`](docs/assets/flix-frame-1.1.step)|<img src="docs/img/frame1.jpg" width=100>|1|
+|Frame main part|3D printed⁴:<br>[`flix-frame-1.1.stl`](docs/assets/flix-frame-1.1.stl) [`flix-frame-1.1.step`](docs/assets/flix-frame-1.1.step)<br>Recommended settings: layer 0.2 mm, line 0.4 mm, infill 100%.|<img src="docs/img/frame1.jpg" width=100>|1|
 |Frame top part|3D printed:<br>[`esp32-holder.stl`](docs/assets/esp32-holder.stl) [`esp32-holder.step`](docs/assets/esp32-holder.step)|<img src="docs/img/esp32-holder.jpg" width=100>|1|
 |Washer for IMU board mounting|3D printed:<br>[`washer-m3.stl`](docs/assets/washer-m3.stl) [`washer-m3.step`](docs/assets/washer-m3.step)|<img src="docs/img/washer-m3.jpg" width=100>|2|
-|*RC transmitter (optional)*|*KINGKONG TINY X8 or other⁵*|<img src="docs/img/tx.jpg" width=100>|1|
+|Controller (recommended)|CC2500 transmitter, like BetaFPV LiteRadio CC2500 (RC receiver/Wi-Fi).<br>Two-sticks gamepad (Wi-Fi only) — see [recommended gamepads](https://docs.qgroundcontrol.com/master/en/qgc-user-guide/setup_view/joystick.html#supported-joysticks).<br>Other⁵|<img src="docs/img/betafpv.jpg" width=100><img src="docs/img/logitech.jpg" width=80>|1|
 |*RC receiver (optional)*|*DF500 or other⁵*|<img src="docs/img/rx.jpg" width=100>|1|
 |Wires|28 AWG recommended|<img src="docs/img/wire-28awg.jpg" width=100>||
 |Tape, double-sided tape||||
 
 *² — barometer is not used for now.*<br>
-*³ — change `MPU9250` to `ICM20948` in `imu.ino` file if using ICM-20948 board.*<br>
+*³ — change `MPU9250` to `ICM20948` or `MPU6050` in `imu.ino` file for using the appropriate boards.*<br>
+*³⁻¹ — MPU-6050 supports I²C interface only (not recommended). To use it change IMU declaration to `MPU6050 IMU(Wire)`.*<br>
 *⁴ — this frame is optimized for GY-91 board, if using other, the board mount holes positions should be modified.*<br>
-*⁵ — you may use any transmitter-receiver pair with SBUS interface.*
+*⁵ — you also may use any transmitter-receiver pair with SBUS interface.*
 
 Tools required for assembly:
 
@@ -90,11 +102,13 @@ Tools required for assembly:
 
 Feel free to modify the design and or code, and create your own improved versions of Flix! Send your results to the [official Telegram chat](https://t.me/opensourcequadcopterchat), or directly to the author ([E-mail](mailto:okalachev@gmail.com), [Telegram](https://t.me/okalachev)).
 
-## Schematics (version 1)
+## Schematics
 
 ### Simplified connection diagram
 
-<img src="docs/img/schematics1.svg" width=800 alt="Flix version 1 schematics">
+<img src="docs/img/schematics1.svg" width=700 alt="Flix version 1 schematics">
+
+*(Dashed is optional).*
 
 Motor connection scheme:
 
@@ -150,10 +164,6 @@ In case of using other IMU orientation, modify the `rotateIMU` function in the `
 
 See [FlixPeriph documentation](https://github.com/okalachev/flixperiph?tab=readme-ov-file#imu-axes-orientation) to learn axis orientation of other IMU boards.
 
-## Version 0
-
-See the information on the obsolete version 0 in the [corresponding article](docs/version0.md).
-
 ## Materials
 
 Subscribe to the Telegram channel on developing the drone and the flight controller (in Russian): https://t.me/opensourcequadcopter.
@@ -161,3 +171,11 @@ Subscribe to the Telegram channel on developing the drone and the flight control
 Join the official Telegram chat: https://t.me/opensourcequadcopterchat.
 
 Detailed article on Habr.com about the development of the drone (in Russian): https://habr.com/ru/articles/814127/.
+
+See the information on the obsolete version 0 in the [corresponding article](docs/version0.md).
+
+## Disclaimer
+
+This is a fun DIY project, and I hope you find it interesting and useful. However, it's not easy to assemble and set up, and it's provided "as is" without any warranties. There’s no guarantee that it will work perfectly — or even work at all.
+
+⚠️ The author is not responsible for any damage, injury, or loss resulting from the use of this project. Use at your own risk!

arduino-cli.yaml

@@ -1,3 +1,5 @@
 board_manager:
   additional_urls:
     - https://raw.githubusercontent.com/espressif/arduino-esp32/gh-pages/package_esp32_index.json
+network:
+  connection_timeout: 1h

docs/book.css

@@ -53,6 +53,12 @@ footer a.telegram, footer a.github {
 	border: 1px solid #c9c9c9;
 }
 
+@media (max-width: 600px) {
+	.MathJax_Display {
+		overflow-x: auto;
+	}
+}
+
 .firmware {
 	position: relative;
 	margin: 20px 0;

docs/book.toml

@@ -10,7 +10,7 @@ description = "Учебник по разработке полетного ко
 build-dir = "build"
 
 [output.html]
-additional-css = ["book.css", "zoom.css"]
+additional-css = ["book.css", "zoom.css", "rotation.css"]
 additional-js = ["zoom.js", "js.js"]
 edit-url-template = "https://github.com/okalachev/flix/blob/master/docs/{path}?plain=1"
 mathjax-support = true

docs/book/SUMMARY.md

@@ -11,6 +11,7 @@
 * [Светодиод]()
 * [Моторы]()
 * [Радиоуправление]()
+* [Вектор, кватернион](geometry.md)
 * [Гироскоп](gyro.md)
 * [Акселерометр]()
 * [Оценка состояния]()

docs/book/firmware.md

@@ -1,8 +1,10 @@
 # Архитектура прошивки
 
-<img src="img/dataflow.svg" width=800 alt="Firmware dataflow diagram">
+Прошивка Flix это обычный скетч Arduino, реализованный в однопоточном стиле. Код инициализации находится в функции `setup()`, а главный цикл — в функции `loop()`. Скетч состоит из нескольких файлов, каждый из которых отвечает за определенную подсистему.
 
-Главный цикл работает на частоте 1000 Гц. Передача данных между подсистемами происходит через глобальные переменные:
+<img src="img/dataflow.svg" width=600 alt="Firmware dataflow diagram">
+
+Главный цикл `loop()` работает на частоте 1000 Гц. Передача данных между подсистемами происходит через глобальные переменные:
 
 * `t` *(float)* — текущее время шага, *с*.
 * `dt` *(float)* — дельта времени между текущим и предыдущим шагами, *с*.
@@ -10,23 +12,39 @@
 * `acc` *(Vector)* — данные с акселерометра, *м/с<sup>2</sup>*.
 * `rates` *(Vector)* — отфильтрованные угловые скорости, *рад/с*.
 * `attitude` *(Quaternion)* — оценка ориентации (положения) дрона.
-* `controls` *(float[])* — пользовательские управляющие сигналы с пульта, нормализованные в диапазоне [-1, 1].
-* `motors` *(float[])* — выходные сигналы на моторы, нормализованные в диапазоне [-1, 1] (возможно вращение в обратную сторону).
+* `controlRoll`, `controlPitch`, ... *(float[])* — команды управления от пилота, в диапазоне [-1, 1].
+* `motors` *(float[])* — выходные сигналы на моторы, в диапазоне [0, 1].
 
 ## Исходные файлы
 
-Исходные файлы прошивки находятся в директории `flix`. Ключевые файлы:
+Исходные файлы прошивки находятся в директории `flix`. Основные файлы:
 
-* [`flix.ino`](https://github.com/okalachev/flix/blob/canonical/flix/flix.ino) — основной входной файл, скетч Arduino. Включает определение глобальных переменных и главный цикл.
-* [`imu.ino`](https://github.com/okalachev/flix/blob/canonical/flix/imu.ino) — чтение данных с датчика IMU (гироскоп и акселерометр), калибровка IMU.
-* [`rc.ino`](https://github.com/okalachev/flix/blob/canonical/flix/rc.ino) — чтение данных с RC-приемника, калибровка RC.
-* [`mavlink.ino`](https://github.com/okalachev/flix/blob/canonical/flix/mavlink.ino) — взаимодействие с QGroundControl через MAVLink.
-* [`estimate.ino`](https://github.com/okalachev/flix/blob/canonical/flix/estimate.ino) — оценка ориентации дрона, комплементарный фильтр.
-* [`control.ino`](https://github.com/okalachev/flix/blob/canonical/flix/control.ino) — управление ориентацией и угловыми скоростями дрона, трехмерный двухуровневый каскадный PID-регулятор.
-* [`motors.ino`](https://github.com/okalachev/flix/blob/canonical/flix/motors.ino) — управление выходными сигналами на моторы через ШИМ.
+* [`flix.ino`](https://github.com/okalachev/flix/blob/master/flix/flix.ino) — основной файл Arduino-скетча. Определяет некоторые глобальные переменные и главный цикл.
+* [`imu.ino`](https://github.com/okalachev/flix/blob/master/flix/imu.ino) — чтение данных с датчика IMU (гироскоп и акселерометр), калибровка IMU.
+* [`rc.ino`](https://github.com/okalachev/flix/blob/master/flix/rc.ino) — чтение данных с RC-приемника, калибровка RC.
+* [`estimate.ino`](https://github.com/okalachev/flix/blob/master/flix/estimate.ino) — оценка ориентации дрона, комплементарный фильтр.
+* [`control.ino`](https://github.com/okalachev/flix/blob/master/flix/control.ino) — подсистема управления, трехмерный двухуровневый каскадный ПИД-регулятор.
+* [`motors.ino`](https://github.com/okalachev/flix/blob/master/flix/motors.ino) — выход PWM на моторы.
+* [`mavlink.ino`](https://github.com/okalachev/flix/blob/master/flix/mavlink.ino) — взаимодействие с QGroundControl или [pyflix](https://github.com/okalachev/flix/tree/master/tools/pyflix) через протокол MAVLink.
 
-Вспомогательные файлы включают:
+Вспомогательные файлы:
 
-* [`vector.h`](https://github.com/okalachev/flix/blob/canonical/flix/vector.h), [`quaternion.h`](https://github.com/okalachev/flix/blob/canonical/flix/quaternion.h) — реализация библиотек векторов и кватернионов проекта.
-* [`pid.h`](https://github.com/okalachev/flix/blob/canonical/flix/pid.h) — реализация общего ПИД-регулятора.
-* [`lpf.h`](https://github.com/okalachev/flix/blob/canonical/flix/lpf.h) — реализация общего фильтра нижних частот.
+* [`vector.h`](https://github.com/okalachev/flix/blob/master/flix/vector.h), [`quaternion.h`](https://github.com/okalachev/flix/blob/master/flix/quaternion.h) — библиотеки векторов и кватернионов.
+* [`pid.h`](https://github.com/okalachev/flix/blob/master/flix/pid.h) — ПИД-регулятор.
+* [`lpf.h`](https://github.com/okalachev/flix/blob/master/flix/lpf.h) — фильтр нижних частот.
+
+### Подсистема управления
+
+Состояние органов управления обрабатывается в функции `interpretControls()` и преобразуется в *команду управления*, которая включает следующее:
+
+* `attitudeTarget` *(Quaternion)* — целевая ориентация дрона.
+* `ratesTarget` *(Vector)* — целевые угловые скорости, *рад/с*.
+* `ratesExtra` *(Vector)* — дополнительные (feed-forward) угловые скорости, для управления рысканием в режиме STAB, *рад/с*.
+* `torqueTarget` *(Vector)* — целевой крутящий момент, диапазон [-1, 1].
+* `thrustTarget` *(float)* — целевая общая тяга, диапазон [0, 1].
+
+Команда управления обрабатывается в функциях `controlAttitude()`, `controlRates()`, `controlTorque()`. Если значение одной из переменных установлено в `NAN`, то соответствующая функция пропускается.
+
+<img src="img/control.svg" width=300 alt="Control subsystem diagram">
+
+Состояние *armed* хранится в переменной `armed`, а текущий режим — в переменной `mode`.

docs/book/geometry.md

@@ -0,0 +1,309 @@
+# Вектор, кватернион
+
+В алгоритме управления квадрокоптером широко применяются геометрические (и алгебраические) объекты, такие как **векторы** и **кватернионы**. Они позволяют упростить математические вычисления и улучшить читаемость кода. В этой главе мы рассмотрим именно те геометрические объекты, которые используются в алгоритме управления квадрокоптером Flix, причем акцент будет сделан на практических аспектах их использования.
+
+## Система координат
+
+### Оси координат
+
+Для работы с объектами в трехмерном пространстве необходимо определить *систему координат*. Как известно, система координат задается тремя взаимно перпендикулярными осями, которые обозначаются как *X*, *Y* и *Z*. Порядок обозначения этих осей зависит от того, какую систему координат мы выбрали — *левую* или *правую*:
+
+|Левая система координат|Правая система координат|
+|-----------------------|------------------------|
+|<img src="img/left-axes.svg" alt="Левая система координат" width="200">|<img src="img/right-axes.svg" alt="Правая система координат" width="200">|
+
+В Flix для всех математических расчетов используется **правая система координат**, что является стандартом в робототехнике и авиации.
+
+Также необходимо выбрать направление осей — в Flix они выбраны в соответствии со стандартом [REP-103](https://www.ros.org/reps/rep-0103.html). Для величин, заданных в подвижной системе координат, связанной с корпусом дрона, применяется порядок <abbr title="Forward Left Up">FLU</abbr>:
+
+* ось X — направлена **вперед**;
+* ось Y — направлена **влево**;
+* ось Z — направлена **вверх**.
+
+Для величин, заданных в *мировой* системе координат (относительно фиксированной точки в пространстве) — <abbr title="East North Up">ENU</abbr>:
+
+* ось X — направлена на **восток** (условный);
+* ось Y — направлена на **север** (условный);
+* ось Z — направлена **вверх**.
+
+> [!NOTE]
+> Для системы ENU важно только взаимное направление осей. Если доступен магнитометр, то используются реальные восток и север, но если нет — то произвольно выбранные.
+
+Углы и угловые скорости определяются в соответствии с правилами математики: значения увеличиваются против часовой стрелки, если смотреть в сторону начала координат. Общий вид системы координат:
+
+<img src="img/axes-rotation.svg" alt="Система координат" width="200">
+
+> [!TIP]
+> Оси координат <i>X</i>, <i>Y</i> и <i>Z</i> часто обозначаются красными, зелеными и синими цветами соответственно. Запомнить это можно с помощью сокращения <abbr title="Red Green Blue">RGB</abbr>.
+
+## Вектор
+
+<div class="firmware">
+	<strong>Файл прошивки:</strong>
+	<a href="https://github.com/okalachev/flix/blob/master/flix/vector.h"><code>vector.h</code></a>.<br>
+</div>
+
+**Вектор** — простой геометрический объект, который содержит три значения, соответствующие координатам *X*, *Y* и *Z*. Эти значения называются *компонентами вектора*. Вектор может описывать точку в пространстве, направление или ось вращения, скорость, ускорение, угловые скорости и другие физические величины. В Flix векторы задаются объектами `Vector` из библиотеки `vector.h`:
+
+```cpp
+Vector v(1, 2, 3);
+v.x = 5;
+v.y = 10;
+v.z = 15;
+```
+
+> [!TIP]
+> Не следует путать геометрический вектор — <code>vector</code> и динамический массив в стандартной библиотеке C++ — <code>std::vector</code>.
+
+В прошивке в виде векторов представлены, например:
+
+* `acc` собственное ускорение с акселерометра.
+* `gyro` — угловые скорости с гироскопа.
+* `rates` — рассчитанная угловая скорость дрона.
+* `accBias`, `accScale`, `gyroBias` — параметры калибровки IMU.
+
+### Операции с векторами
+
+**Длина вектора** рассчитывается при помощи теоремы Пифагора; в прошивке используется метод `norm()`:
+
+```cpp
+Vector v(3, 4, 5);
+float length = v.norm(); // 7.071
+```
+
+Любой вектор можно привести к **единичному вектору** (сохранить направление, но сделать длину равной 1) при помощи метода `normalize()`:
+
+```cpp
+Vector v(3, 4, 5);
+v.normalize(); // 0.424, 0.566, 0.707
+```
+
+**Сложение и вычитание** векторов реализуется через простое покомпонентное сложение и вычитание. Геометрически сумма векторов представляет собой вектор, который соединяет начало первого вектора с концом второго. Разность векторов представляет собой вектор, который соединяет конец первого вектора с концом второго. Это удобно для расчета относительных позиций, суммарных скоростей и решения других задач. В коде эти операции интуитивно понятны:
+
+```cpp
+Vector a(1, 2, 3);
+Vector b(4, 5, 6);
+Vector sum = a + b; // 5, 7, 9
+Vector diff = a - b; // -3, -3, -3
+```
+
+Операция **умножения на число** `n` увеличивает (или уменьшает) длину вектора в `n` раз (сохраняя направление):
+
+```cpp
+Vector a(1, 2, 3);
+Vector b = a * 2; // 2, 4, 6
+```
+
+В некоторых случаях полезна операция **покомпонентного умножения** (или деления) векторов. Например, для применения коэффициентов калибровки к данным с IMU. В разных библиотеках эта операция обозначается по разному, но в библиотеке `vector.h` используется простые знаки `*` и `/`:
+
+```cpp
+acc = acc / accScale;
+```
+
+**Угол между векторами** можно найти при помощи статического метода `Vector::angleBetween()`:
+
+```cpp
+Vector a(1, 0, 0);
+Vector b(0, 1, 0);
+float angle = Vector::angleBetween(a, b); // 1.57 (90 градусов)
+```
+
+#### Скалярное произведение
+
+Скалярное произведение векторов (*dot product*) — это произведение длин двух векторов на косинус угла между ними. В математике оно обозначается знаком `·` или слитным написанием векторов. Интуитивно, результат скалярного произведения показывает, насколько два вектора *сонаправлены*.
+
+В Flix используется статический метод `Vector::dot()`:
+
+```cpp
+Vector a(1, 2, 3);
+Vector b(4, 5, 6);
+float dotProduct = Vector::dot(a, b); // 32
+```
+
+Операция скалярного произведения может помочь, например, при расчете проекции одного вектора на другой.
+
+#### Векторное произведение
+
+Векторное произведение (*cross product*) позволяет найти вектор, перпендикулярный двум другим векторам. В математике оно обозначается знаком `×`, а в прошивке используется статический метод `Vector::cross()`:
+
+```cpp
+Vector a(1, 2, 3);
+Vector b(4, 5, 6);
+Vector crossProduct = Vector::cross(a, b); // -3, 6, -3
+```
+
+## Кватернион
+
+### Ориентация в трехмерном пространстве
+
+В отличие от позиции и скорости, у ориентации в трехмерном пространстве нет универсального для всех случаев способа представления. В зависимости от задачи ориентация может быть представлена в виде *углов Эйлера*, *матрицы поворота*, *вектора вращения* или *кватерниона*. Рассмотрим используемые в полетной прошивке способы представления ориентации.
+
+### Углы Эйлера
+
+**Углы Эйлера** — *крен*, *тангаж* и *рыскание* — это наиболее «естественный» для человека способ представления ориентации. Они описывают последовательные вращения объекта вокруг трех осей координат.
+
+В прошивке углы Эйлера сохраняются в обычный объект `Vector` (хоть и, строго говоря, не являются вектором):
+
+* Угол по крену (*roll*) — `vector.x`.
+* Угол по тангажу (*pitch*) — `vector.y`.
+* Угол по рысканию (*yaw*) — `vector.z`.
+
+Особенности углов Эйлера:
+
+1. Углы Эйлера зависят от порядка применения вращений, то есть существует 6 типов углов Эйлера. Порядок вращений, принятый в Flix (и в роботехнике в целом) — рыскание, тангаж, крен (ZYX).
+2. Для некоторых ориентаций углы Эйлера «вырождаются». Так, если объект «смотрит» строго вниз, то угол по рысканию и угол по крену становятся неразличимыми. Эта ситуация называется *gimbal lock* — потеря одной степени свободы.
+
+Ввиду этих особенности для углов Эйлера не существует общих формул для самых базовых задач с ориентациями, таких как применение одного вращения (ориентации) к другому, расчет разницы между ориентациями и подобных. Поэтому в основном углы Эйлера применяются в пользовательском интерфейсе, но редко используются в математических расчетах.
+
+> [!IMPORTANT]
+> Для углов Эйлера не существует общих формул для самых базовых операций с ориентациями.
+
+### Axis-angle
+
+Помимо углов Эйлера, любую ориентацию в трехмерном пространстве можно представить в виде вращения вокруг некоторой оси на некоторый угол. В геометрии это доказывается, как **теорема вращения Эйлера**. В таком представлении ориентация задается двумя величинами:
+
+* **Ось вращения** (*axis*) — единичный вектор, определяющий ось вращения.
+* **Угол поворота** (*angle* или *θ*) — угол, на который нужно повернуть объект вокруг этой оси.
+
+В Flix ось вращения задается объектом `Vector`, а угол поворота — числом типа `float` в радианах:
+
+```cpp
+// Вращение на 45 градусов вокруг оси (1, 2, 3)
+Vector axis(1, 2, 3);
+float angle = radians(45);
+```
+
+Этот способ более удобен для расчетов, чем углы Эйлера, но все еще не является оптимальным.
+
+### Вектор вращения
+
+Если умножить вектор *axis* на угол поворота *θ*, то получится **вектор вращения** (*rotation vector*). Этот вектор играет важную роль в алгоритмах управления ориентацией летательного аппарата.
+
+Вектор вращения обладает замечательным свойством: если угловые скорости объекта (в собственной системе координат) в каждый момент времени совпадают с компонентами этого вектора, то за единичное время объект придет к заданной этим вектором ориентации. Это свойство позволяет использовать вектор вращения для управления ориентацией объекта посредством управления угловыми скоростями.
+
+> [!IMPORTANT]
+> Чтобы за единичное время прийти к заданной ориентации, собственные угловые скорости объекта должны быть равны компонентам вектора вращения.
+
+Вектора вращения в Flix представляются в виде объектов `Vector`:
+
+```cpp
+// Вращение на 45 градусов вокруг оси (1, 2, 3)
+Vector rotation = radians(45) * Vector(1, 2, 3);
+```
+
+### Кватернион
+
+<div class="firmware">
+	<strong>Файл прошивки:</strong>
+	<a href="https://github.com/okalachev/flix/blob/master/flix/quaternion.h"><code>quaternion.h</code></a>.<br>
+</div>
+
+Вектор вращения удобен, но еще удобнее использовать **кватернион**. В Flix кватернионы задаются объектами `Quaternion` из библиотеки `quaternion.h`. Кватернион состоит из четырех значений: *w*, *x*, *y*, *z* и рассчитывается из вектора оси вращения (*axis*) и угла поворота (*θ*) по формуле:
+
+\\[ q = \left( \begin{array}{c} w \\\\ x \\\\ y \\\\ z \end{array} \right) = \left( \begin{array}{c} \cos\left(\frac{\theta}{2}\right) \\\\ axis\_x \cdot \sin\left(\frac{\theta}{2}\right) \\\\ axis\_y \cdot \sin\left(\frac{\theta}{2}\right) \\\\ axis\_z \cdot \sin\left(\frac{\theta}{2}\right) \end{array} \right) \\]
+
+На практике оказывается, что **именно такое представление наиболее удобно для математических расчетов**.
+
+Проиллюстрируем кватернион и описанные выше способы представления ориентации на интерактивной визуализации. Изменяйте угол поворота *θ* с помощью ползунка (ось вращения константна) и изучите, как меняется ориентация объекта, вектор вращения и кватернион:
+
+<div id="rotation-diagram" class="diagram">
+	<p>
+		<label class="angle" for="angle-range"></label>
+		<input type="range" name="angle" id="angle-range" min="0" max="360" value="0" step="1">
+	</p>
+	<p class="axis"></p>
+	<p class="rotation-vector"></p>
+	<p class="quaternion"></p>
+	<p class="euler"></p>
+</div>
+
+<script type="importmap">
+{
+	"imports": {
+		"three": "https://cdn.jsdelivr.net/npm/three@0.176.0/build/three.module.js",
+		"three/addons/": "https://cdn.jsdelivr.net/npm/three@0.176.0/examples/jsm/"
+	}
+}
+</script>
+<script type="module" src="js/rotation.js"></script>
+
+> [!IMPORTANT]
+> В контексте управляющих алгоритмов кватернион — это оптимизированный для расчетов аналог вектора вращения.
+
+Кватернион это наиболее часто используемый способ представления ориентации в алгоритмах. Кроме этого, у кватерниона есть большое значение в теории чисел и алгебре, как у расширения понятия комплексного числа, но рассмотрение этого аспекта выходит за рамки описания работы с вращениями с практической точки зрения.
+
+В прошивке в виде кватернионов представлены, например:
+
+* `attitude` — текущая ориентация квадрокоптера.
+* `attitudeTarget` — целевая ориентация квадрокоптера.
+
+### Операции с кватернионами
+
+Кватернион создается напрямую из четырех его компонент:
+
+```cpp
+// Кватернион, представляющий нулевую (исходную) ориентацию
+Quaternion q(1, 0, 0, 0);
+```
+
+Кватернион можно создать из оси вращения и угла поворота, вектора вращения или углов Эйлера:
+
+```cpp
+Quaternion q1 = Quaternion::fromAxisAngle(axis, angle);
+Quaternion q2 = Quaternion::fromRotationVector(rotation);
+Quaternion q3 = Quaternion::fromEuler(Vector(roll, pitch, yaw));
+```
+
+И наоборот:
+
+```cpp
+q1.toAxisAngle(axis, angle);
+Vector rotation = q2.toRotationVector();
+Vector euler = q3.toEuler();
+```
+
+Возможно рассчитать вращение между двумя обычными векторами:
+
+```cpp
+Quaternion q = Quaternion::fromBetweenVectors(v1, v2); // в виде кватерниона
+Vector rotation = Vector::rotationVectorBetween(v1, v2); // в виде вектора вращения
+```
+
+Шорткаты для работы с углом Эйлера по рысканью (удобно для алгоритмов управления полетом):
+
+```cpp
+float yaw = q.getYaw();
+q.setYaw(yaw);
+```
+
+#### Применения вращений
+
+Чтобы применить вращение, выраженное в кватернионе, к другому кватерниону, в математике используется операция **умножения кватернионов**. При использовании этой операции, необходимо учитывать, что она не является коммутативной, то есть порядок операндов имеет значение. Формула умножения кватернионов выглядит так:
+
+\\[ q_1 \times q_2 = \left( \begin{array}{c} w_1 \\\\ x_1 \\\\ y_1 \\\\ z_1 \end{array} \right) \times \left( \begin{array}{c} w_2 \\\\ x_2 \\\\ y_2 \\\\ z_2 \end{array} \right) = \left( \begin{array}{c} w_1 w_2 - x_1 x_2 - y_1 y_2 - z_1 z_2 \\\\ w_1 x_2 + x_1 w_2 + y_1 z_2 - z_1 y_2 \\\\ w_1 y_2 - x_1 z_2 + y_1 w_2 + z_1 x_2 \\\\ w_1 z_2 + x_1 y_2 - y_1 x_2 + z_1 w_2 \end{array} \right) \\]
+
+В библиотеке `quaternion.h` для этой операции используется статический метод `Quaternion::rotate()`:
+
+```cpp
+// Композиция вращений q1 и q2
+Quaternion result = Quaternion::rotate(q1, q2);
+```
+
+Также полезной является операция применения вращения к вектору, которая делается похожим образом:
+
+```cpp
+// Вращение вектора v кватернионом q
+Vector result = Quaternion::rotateVector(v, q);
+```
+
+Для расчета разницы между двумя ориентациями используется метод `Quaternion::between()`:
+
+```cpp
+// Расчет вращения от q1 к q2
+Quaternion q = Quaternion::between(q1, q2);
+```
+
+## Дополнительные материалы
+
+* [Интерактивный учебник по кватернионам](https://eater.net/quaternions).
+* [Визуализация вращения вектора с помощью кватернионов](https://quaternions.online).

docs/book/gyro.md

@@ -1,7 +1,7 @@
 # Гироскоп
 
 <div class="firmware">
-	<strong>Файл прошивки Flix:</strong>
+	<strong>Файл прошивки:</strong>
 	<a href="https://github.com/okalachev/flix/blob/canonical/flix/imu.ino"><code>imu.ino</code></a> <small>(каноничная версия)</small>.<br>
 	Текущая версия: <a href="https://github.com/okalachev/flix/blob/master/flix/imu.ino"><code>imu.ino</code></a>.
 </div>
@@ -100,7 +100,7 @@ void setup() {
 
 Для однократного считывания данных используется метод `read()`. Затем данные с гироскопа получаются при помощи метода `getGyro(x, y, z)`. Этот метод записывает в переменные `x`, `y` и `z` угловые скорости вокруг соответствующих осей в радианах в секунду.
 
-Если нужно гарантировать, что будут считаны новые данные, можно использовать метод `waitForData()`. Этот метод блокирует выполнение программы до тех пор, пока в IMU не появятся новые данные. Метод `waitForData()` позволяет привязать частоту главного цикла `loop` к частоте обновления данных IMU. Это удобно для организации главного цикла управления квадрокоптером.
+Если нужно гарантировать, что будут считаны новые данные, можно использовать метод `waitForData()`. Этот метод блокирует выполнение программы до тех пор, пока в IMU не появятся новые данные. Метод `waitForData()` позволяет привязать частоту главного цикла `loop` к частоте обновления данных IMU. Это удобно для организации главного цикла управления квадрокоптером.
 
 Программа для чтения данных с гироскопа и вывода их в консоль для построения графиков в Serial Plotter выглядит так:
 
@@ -153,7 +153,7 @@ IMU.setRate(IMU.RATE_1KHZ_APPROX);
 
 * `RATE_MIN` — минимальная частота сэмплов для конкретного IMU.
 * `RATE_50HZ_APPROX` — значение, близкое к 50 Гц.
-* `RATE_1KHZ_APPROX`  — значение, близкое к 1 кГц.
+* `RATE_1KHZ_APPROX` — значение, близкое к 1 кГц.
 * `RATE_8KHZ_APPROX` — значение, близкое к 8 кГц.
 * `RATE_MAX` — максимальная частота сэмплов для конкретного IMU.
 

docs/book/js/rotation.js

@@ -0,0 +1,262 @@
+import * as THREE from 'three';
+import { SVGRenderer, SVGObject } from 'three/addons/renderers/SVGRenderer.js';
+import { OrbitControls } from 'three/addons/controls/OrbitControls.js';
+
+const diagramEl = document.getElementById('rotation-diagram');
+
+const scene = new THREE.Scene();
+scene.background = new THREE.Color(0xffffff);
+
+const camera = new THREE.OrthographicCamera();
+
+camera.position.set(9, 26, 20);
+camera.up.set(0, 0, 1);
+camera.lookAt(0, 0, 0);
+
+const renderer = new SVGRenderer();
+diagramEl.prepend(renderer.domElement);
+
+const controls = new OrbitControls(camera, renderer.domElement);
+controls.enableZoom = false;
+
+const LINE_WIDTH = 4;
+
+function createLabel(text, x, y, z, min = false) {
+	const label = document.createElementNS('http://www.w3.org/2000/svg', 'text');
+	label.setAttribute('class', 'label' + (min ? ' min' : ''));
+	label.textContent = text;
+	label.setAttribute('y', -15);
+	const object = new SVGObject(label);
+	object.position.x = x;
+	object.position.y = y;
+	object.position.z = z;
+	return object;
+}
+
+function createLine(x1, y1, z1, x2, y2, z2, color) {
+	const geometry = new THREE.BufferGeometry().setFromPoints([
+		new THREE.Vector3(x1, y1, z1),
+		new THREE.Vector3(x2, y2, z2)
+	]);
+	const material = new THREE.LineBasicMaterial({ color: color, linewidth: LINE_WIDTH, transparent: true, opacity: 0.8 });
+	const line = new THREE.Line(geometry, material);
+	scene.add(line);
+	return line;
+}
+
+function changeLine(line, x1, y1, z1, x2, y2, z2) {
+	line.geometry.setFromPoints([new THREE.Vector3(x1, y1, z1), new THREE.Vector3(x2, y2, z2)]);
+	return line;
+}
+
+function createVector(x1, y1, z1, x2, y2, z2, color, label = '') {
+	const HEAD_LENGTH = 1;
+	const HEAD_WIDTH = 0.2;
+
+	const group = new THREE.Group();
+	const direction = new THREE.Vector3(x2 - x1, y2 - y1, z2 - z1).normalize();
+	const norm = new THREE.Vector3(x2 - x1, y2 - y1, z2 - z1).length();
+	let end = new THREE.Vector3(x2, y2, z2);
+
+	if (norm > HEAD_LENGTH) {
+		end = new THREE.Vector3(x2 - direction.x * HEAD_LENGTH / 2, y2 - direction.y * HEAD_LENGTH / 2, z2 - direction.z * HEAD_LENGTH / 2);
+	}
+
+	// create line
+	const geometry = new THREE.BufferGeometry().setFromPoints([new THREE.Vector3(x1, y1, z1), end]);
+	const material = new THREE.LineBasicMaterial({ color: color, linewidth: LINE_WIDTH, transparent: true, opacity: 0.8 });
+	const line = new THREE.Line(geometry, material);
+	group.add(line);
+
+	if (norm > HEAD_LENGTH) {
+		// Create arrow
+		const arrowGeometry = new THREE.ConeGeometry(HEAD_WIDTH, HEAD_LENGTH, 16);
+		const arrowMaterial = new THREE.MeshBasicMaterial({ color: color });
+		const arrow = new THREE.Mesh(arrowGeometry, arrowMaterial);
+		arrow.position.set(x2 - direction.x * HEAD_LENGTH / 2, y2 - direction.y * HEAD_LENGTH / 2, z2 - direction.z * HEAD_LENGTH / 2);
+		arrow.lookAt(new THREE.Vector3(x1, y1, z1));
+		arrow.rotateX(-Math.PI / 2);
+		group.add(arrow);
+	}
+
+	// create label
+	if (label) group.add(createLabel(label, x2, y2, z2));
+	scene.add(group);
+	return group;
+}
+
+function changeVector(vector, x1, y1, z1, x2, y2, z2, color, label = '') {
+	vector.removeFromParent();
+	return createVector(x1, y1, z1, x2, y2, z2, color, label);
+}
+
+function createDrone(x, y, z) {
+	const group = new THREE.Group();
+
+	// Fuselage and wing triangle (main body)
+	const fuselageGeometry = new THREE.BufferGeometry();
+	const fuselageVertices = new Float32Array([
+		1, 0, 0,
+		-1, 0.6, 0,
+		-1, -0.6, 0
+	]);
+	fuselageGeometry.setAttribute('position', new THREE.BufferAttribute(fuselageVertices, 3));
+	const fuselageMaterial = new THREE.MeshBasicMaterial({ color: 0xb3b3b3, side: THREE.DoubleSide, transparent: true, opacity: 0.8 });
+	const fuselage = new THREE.Mesh(fuselageGeometry, fuselageMaterial);
+	group.add(fuselage);
+
+	// Tail triangle
+	const tailGeometry = new THREE.BufferGeometry();
+	const tailVertices = new Float32Array([
+		-0.2, 0, 0,
+		-1, 0, 0,
+		-1, 0, 0.5,
+	]);
+	tailGeometry.setAttribute('position', new THREE.BufferAttribute(tailVertices, 3));
+	const tailMaterial = new THREE.MeshBasicMaterial({ color: 0xd80100, side: THREE.DoubleSide, transparent: true, opacity: 0.9 });
+	const tail = new THREE.Mesh(tailGeometry, tailMaterial);
+	group.add(tail);
+
+	group.position.set(x, y, z);
+	group.scale.set(2, 2, 2);
+	scene.add(group);
+	return group;
+}
+
+// Create axes
+const AXES_LENGTH = 10;
+createVector(0, 0, 0, AXES_LENGTH, 0, 0, 0xd80100, 'x');
+createVector(0, 0, 0, 0, AXES_LENGTH, 0, 0x0076ba, 'y');
+createVector(0, 0, 0, 0, 0, AXES_LENGTH, 0x57ed00, 'z');
+
+// Rotation values
+const rotationAxisSrc = new THREE.Vector3(2, 1, 3);
+let rotationAngle = 0;
+let rotationAxis = rotationAxisSrc.clone().normalize();
+let rotationVector = new THREE.Vector3(rotationAxis.x * rotationAngle, rotationAxis.y * rotationAngle, rotationAxis.z * rotationAngle);
+
+let rotationVectorObj = createVector(0, 0, 0, rotationVector.x, rotationVector.y, rotationVector.z, 0xff9900);
+let axisObj = createLine(0, 0, 0, rotationAxis.x * AXES_LENGTH, rotationAxis.y * AXES_LENGTH, rotationAxis.z * AXES_LENGTH, 0xe8e8e8);
+
+const drone = createDrone(0, 0, 0);
+
+// UI
+const angleInput = diagramEl.querySelector('input[name=angle]');
+const rotationVectorEl = diagramEl.querySelector('.rotation-vector');
+const angleEl = diagramEl.querySelector('.angle');
+const quaternionEl = diagramEl.querySelector('.quaternion');
+const eulerEl = diagramEl.querySelector('.euler');
+diagramEl.querySelector('.axis').innerHTML = `<b style='color:#b6b6b6'>Ось вращения:</b> (${rotationAxisSrc.x}, ${rotationAxisSrc.y}, ${rotationAxisSrc.z}) ∥ (${rotationAxis.x.toFixed(1)}, ${rotationAxis.y.toFixed(1)}, ${rotationAxis.z.toFixed(1)})`;
+
+function updateScene() {
+	rotationAngle = parseFloat(angleInput.value) * Math.PI / 180;
+	rotationVector.set(rotationAxis.x * rotationAngle, rotationAxis.y * rotationAngle, rotationAxis.z * rotationAngle);
+	rotationVectorObj = changeVector(rotationVectorObj, 0, 0, 0, rotationVector.x, rotationVector.y, rotationVector.z, 0xff9900);
+
+	// rotate drone
+	drone.rotation.set(0, 0, 0);
+	drone.rotateOnAxis(rotationAxis, rotationAngle);
+
+	// update labels
+	angleEl.innerHTML = `<b>Угол вращения:</b> ${parseFloat(angleInput.value).toFixed(0)}° = ${(rotationAngle).toFixed(2)} рад`;
+	rotationVectorEl.innerHTML = `<b style='color:#e49a44'>Вектор вращения:</b> (${rotationVector.x.toFixed(1)}, ${rotationVector.y.toFixed(1)}, ${rotationVector.z.toFixed(1)}) рад`;
+
+	let quaternion = new THREE.Quaternion();
+	quaternion.setFromAxisAngle(rotationAxis, rotationAngle);
+
+	quaternionEl.innerHTML = `<b>Кватернион:</b>
+		<math xmlns="http://www.w3.org/1998/Math/MathML">
+			<mrow>
+				<mo>(</mo>
+				<mrow>
+					<mi>cos</mi>
+					<mo>(</mo>
+					<mfrac>
+						<mi>${rotationAngle.toFixed(2)}</mi>
+						<mn>2</mn>
+					</mfrac>
+					<mo>)</mo>
+				</mrow>
+				<mo>, </mo>
+				<mrow>
+					<mi>${rotationAxis.x.toFixed(1)}</mi>
+					<mo>·</mo>
+					<mi>sin</mi>
+					<mo>(</mo>
+					<mfrac>
+						<mi>${rotationAngle.toFixed(2)}</mi>
+						<mn>2</mn>
+					</mfrac>
+					<mo>)</mo>
+				</mrow>
+				<mo>, </mo>
+				<mrow>
+					<mi>${rotationAxis.y.toFixed(1)}</mi>
+					<mo>·</mo>
+					<mi>sin</mi>
+					<mo>(</mo>
+					<mfrac>
+						<mi>${rotationAngle.toFixed(2)}</mi>
+						<mn>2</mn>
+					</mfrac>
+					<mo>)</mo>
+				</mrow>
+				<mo>,</mo>
+				<mrow>
+					<mi>${rotationAxis.z.toFixed(1)}</mi>
+					<mo>·</mo>
+					<mi>sin</mi>
+					<mo>(</mo>
+					<mfrac>
+						<mi>${rotationAngle.toFixed(2)}</mi>
+						<mn>2</mn>
+					</mfrac>
+					<mo>)</mo>
+				</mrow>
+				<mo>)</mo>
+			</mrow>
+		</math>
+		= (${quaternion.w.toFixed(1)}, ${(quaternion.x).toFixed(1)}, ${(quaternion.y).toFixed(1)}, ${(quaternion.z).toFixed(1)})`;
+
+	eulerEl.innerHTML = `<b>Углы Эйлера:</b> крен ${(drone.rotation.x * 180 / Math.PI).toFixed(0)}°,
+		 тангаж ${(drone.rotation.y * 180 / Math.PI).toFixed(0)}°, рыскание ${(drone.rotation.z * 180 / Math.PI).toFixed(0)}°`;
+}
+
+function updateCamera() {
+	const RANGE = 8;
+	const VERT_SHIFT = 2;
+	const HOR_SHIFT = -2;
+	const width = renderer.domElement.clientWidth;
+	const height = renderer.domElement.clientHeight;
+	const ratio = width / height;
+	if (ratio > 1) {
+		camera.left = -RANGE * ratio;
+		camera.right = RANGE * ratio;
+		camera.top = RANGE + VERT_SHIFT;
+		camera.bottom = -RANGE + VERT_SHIFT;
+	} else {
+		camera.left = -RANGE + HOR_SHIFT;
+		camera.right = RANGE + HOR_SHIFT;
+		camera.top = RANGE / ratio + VERT_SHIFT;
+		camera.bottom = -RANGE / ratio + VERT_SHIFT;
+	}
+	camera.updateProjectionMatrix();
+	renderer.setSize(width, height);
+}
+
+function update() {
+	// requestAnimationFrame(update);
+	updateCamera();
+	updateScene();
+	controls.update();
+	renderer.render(scene, camera);
+}
+update();
+
+window.addEventListener('resize', update);
+angleInput.addEventListener('input', update);
+angleInput.addEventListener('change', update);
+diagramEl.addEventListener('mousemove', update);
+diagramEl.addEventListener('touchmove', update);
+diagramEl.addEventListener('scroll', update);
+diagramEl.addEventListener('wheel', update);

docs/build.md

@@ -1,205 +0,0 @@
-# Building and running
-
-To build the firmware or the simulator, you need to clone the repository using git:
-
-```bash
-git clone https://github.com/okalachev/flix.git
-cd flix
-```
-
-## Simulation
-
-### Ubuntu 20.04
-
-The latest version of Ubuntu supported by Gazebo 11 simulator is 20.04. If you have a newer version, consider using a virtual machine.
-
-1. Install Arduino CLI:
-
-   ```bash
-   curl -fsSL https://raw.githubusercontent.com/arduino/arduino-cli/master/install.sh | BINDIR=~/.local/bin sh
-   ```
-
-2. Install Gazebo 11:
-
-   ```bash
-   curl -sSL http://get.gazebosim.org | sh
-   ```
-
-   Set up your Gazebo environment variables:
-
-   ```bash
-   echo "source /usr/share/gazebo/setup.sh" >> ~/.bashrc
-   source ~/.bashrc
-   ```
-
-3. Install SDL2 and other dependencies:
-
-   ```bash
-   sudo apt-get update && sudo apt-get install build-essential libsdl2-dev
-   ```
-
-4. Add your user to the `input` group to enable joystick support (you need to re-login after this command):
-
-   ```bash
-   sudo usermod -a -G input $USER
-   ```
-
-5. Run the simulation:
-
-   ```bash
-   make simulator
-   ```
-
-### macOS
-
-1. Install Homebrew package manager, if you don't have it installed:
-
-   ```bash
-   /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"
-   ```
-
-2. Install Arduino CLI, Gazebo 11 and SDL2:
-
-   ```bash
-   brew tap osrf/simulation
-   brew install arduino-cli
-   brew install gazebo11
-   brew install sdl2
-   ```
-
-   Set up your Gazebo environment variables:
-
-   ```bash
-   echo "source /opt/homebrew/share/gazebo/setup.sh" >> ~/.zshrc
-   source ~/.zshrc
-   ```
-
-3. Run the simulation:
-
-   ```bash
-   make simulator
-   ```
-
-### Setup and flight
-
-#### Control with smartphone
-
-1. Install [QGroundControl mobile app](https://docs.qgroundcontrol.com/master/en/qgc-user-guide/getting_started/download_and_install.html#android) on your smartphone. For **iOS**, use [QGroundControl build from TAJISOFT](https://apps.apple.com/ru/app/qgc-from-tajisoft/id1618653051).
-2. Connect your smartphone to the same Wi-Fi network as the machine running the simulator.
-3. If you're using a virtual machine, make sure that its network is set to the **bridged** mode with Wi-Fi adapter selected.
-4. Run the simulation.
-5. Open QGroundControl app. It should connect and begin showing the virtual drone's telemetry automatically.
-6. Go to the settings and enable *Virtual Joystick*. *Auto-Center Throttle* setting **should be disabled**.
-7. Use the virtual joystick to fly the drone!
-
-#### Control with USB remote control
-
-1. Connect your USB remote control to the machine running the simulator.
-2. Run the simulation.
-3. Calibrate the RC using `cr` command in the command line interface.
-4. Run the simulation again.
-5. Use the USB remote control to fly the drone!
-
-## Firmware
-
-### Arduino IDE (Windows, Linux, macOS)
-
-1. Install [Arduino IDE](https://www.arduino.cc/en/software) (version 2 is recommended).
-2. Windows users might need to install [USB to UART bridge driver from Silicon Labs](https://www.silabs.com/developers/usb-to-uart-bridge-vcp-drivers).
-3. Install ESP32 core, version 3.1.0 (version 2.x is not supported). See the [official Espressif's instructions](https://docs.espressif.com/projects/arduino-esp32/en/latest/installing.html#installing-using-arduino-ide) on installing ESP32 Core in Arduino IDE.
-4. Install the following libraries using [Library Manager](https://docs.arduino.cc/software/ide-v2/tutorials/ide-v2-installing-a-library):
-   * `FlixPeriph`, the latest version.
-   * `MAVLink`, version 2.0.12.
-5. Clone the project using git or [download the source code as a ZIP archive](https://codeload.github.com/okalachev/flix/zip/refs/heads/master).
-6. Open the downloaded Arduino sketch `flix/flix.ino` in Arduino IDE.
-7. Connect your ESP32 board to the computer and choose correct board type in Arduino IDE (*WEMOS D1 MINI ESP32* for ESP32 Mini) and the port.
-8. [Build and upload](https://docs.arduino.cc/software/ide-v2/tutorials/getting-started/ide-v2-uploading-a-sketch) the firmware using Arduino IDE.
-
-### Command line (Windows, Linux, macOS)
-
-1. [Install Arduino CLI](https://arduino.github.io/arduino-cli/installation/).
-
-   On Linux, use:
-
-   ```bash
-   curl -fsSL https://raw.githubusercontent.com/arduino/arduino-cli/master/install.sh | BINDIR=~/.local/bin sh
-   ```
-
-2. Windows users might need to install [USB to UART bridge driver from Silicon Labs](https://www.silabs.com/developers/usb-to-uart-bridge-vcp-drivers).
-3. Compile the firmware using `make`. Arduino dependencies will be installed automatically:
-
-   ```bash
-   make
-   ```
-
-   You can flash the firmware to the board using command:
-
-   ```bash
-   make upload
-   ```
-
-   You can also compile the firmware, upload it and start serial port monitoring using command:
-
-   ```bash
-   make upload monitor
-   ```
-
-See other available Make commands in the [Makefile](../Makefile).
-
-> [!TIP]
-> You can test the firmware on a bare ESP32 board without connecting IMU and other peripherals. The Wi-Fi network `flix` should appear and all the basic functionality including CLI and QGroundControl connection should work.
-
-### Setup and flight
-
-Before flight you need to calibrate the accelerometer:
-
-1. Open Serial Monitor in Arduino IDE (or use `make monitor` command in the command line).
-2. Type `ca` command there and follow the instructions.
-
-#### Control with smartphone
-
-1. Install [QGroundControl mobile app](https://docs.qgroundcontrol.com/master/en/qgc-user-guide/getting_started/download_and_install.html#android) on your smartphone.
-2. Power the drone using the battery.
-3. Connect your smartphone to the appeared `flix` Wi-Fi network.
-4. Open QGroundControl app. It should connect and begin showing the drone's telemetry automatically.
-5. Go to the settings and enable *Virtual Joystick*. *Auto-Center Throttle* setting **should be disabled**.
-6. Use the virtual joystick to fly the drone!
-
-#### Control with remote control
-
-Before flight using remote control, you need to calibrate it:
-
-1. Open Serial Monitor in Arduino IDE (or use `make monitor` command in the command line).
-2. Type `cr` command there and follow the instructions.
-3. Use the remote control to fly the drone!
-
-#### Control with USB remote control
-
-If your drone doesn't have RC receiver installed, you can use USB remote control and QGroundControl app to fly it.
-
-1. Install [QGroundControl](https://docs.qgroundcontrol.com/master/en/qgc-user-guide/getting_started/download_and_install.html) app on your computer.
-2. Connect your USB remote control to the computer.
-3. Power up the drone.
-4. Connect your computer to the appeared `flix` Wi-Fi network.
-5. Launch QGroundControl app. It should connect and begin showing the drone's telemetry automatically.
-6. Go the the QGroundControl menu ⇒ *Vehicle Setup* ⇒ *Joystick*. Calibrate you USB remote control there.
-7. Use the USB remote control to fly the drone!
-
-#### Adjusting parameters
-
-You can adjust some of the drone's parameters (include PID coefficients) in QGroundControl app. In order to do that, go to the QGroundControl menu ⇒ *Vehicle Setup* ⇒ *Parameters*.
-
-<img src="img/parameters.png" width="400">
-
-#### CLI access
-
-In addition to accessing the drone's command line interface (CLI) using the serial port, you can also access it with QGroundControl using Wi-Fi connection. To do that, go to the QGroundControl menu ⇒ *Vehicle Setup* ⇒ *Analyze Tools* ⇒ *MAVLink Console*.
-
-<img src="img/cli.png" width="400">
-
-> [!NOTE]
-> If something goes wrong, go to the [Troubleshooting](troubleshooting.md) article.
-
-### Firmware code structure
-
-See [firmware overview](firmware.md) for more details.

docs/build.md

@@ -0,0 +1 @@
+usage.md

docs/firmware.md

@@ -1,37 +1,56 @@
 # Firmware overview
 
+The firmware is a regular Arduino sketch, and it follows the classic Arduino one-threaded design. The initialization code is in the `setup()` function, and the main loop is in the `loop()` function. The sketch includes several files, each responsible for a specific subsystem.
+
 ## Dataflow
 
-<img src="img/dataflow.svg" width=800 alt="Firmware dataflow diagram">
+<img src="img/dataflow.svg" width=600 alt="Firmware dataflow diagram">
 
-The main loop is running at 1000 Hz. All the dataflow is happening through global variables (for simplicity):
+The main loop is running at 1000 Hz. All the dataflow goes through global variables (for simplicity):
 
-* `t` *(double)* — current step time, *s*.
+* `t` *(float)* — current step time, *s*.
 * `dt` *(float)* — time delta between the current and previous steps, *s*.
 * `gyro` *(Vector)* — data from the gyroscope, *rad/s*.
 * `acc` *(Vector)* — acceleration data from the accelerometer, *m/s<sup>2</sup>*.
 * `rates` *(Vector)* — filtered angular rates, *rad/s*.
 * `attitude` *(Quaternion)* — estimated attitude (orientation) of drone.
-* `controls` *(float[])* — user control inputs from the RC, normalized to [-1, 1] range.
-* `motors` *(float[])* — motor outputs, normalized to [-1, 1] range; reverse rotation is possible.
+* `controlRoll`, `controlPitch`, ... *(float[])* — pilot control inputs, range [-1, 1].
+* `motors` *(float[])* — motor outputs, range [0, 1].
 
 ## Source files
 
-Firmware source files are located in `flix` directory. The key files are:
+Firmware source files are located in `flix` directory. The core files are:
 
-* [`flix.ino`](../flix/flix.ino) — main entry point, Arduino sketch. Includes global variables definition and the main loop.
+* [`flix.ino`](../flix/flix.ino) — Arduino sketch main file, entry point.Includes some global variable definitions and the main loop.
 * [`imu.ino`](../flix/imu.ino) — reading data from the IMU sensor (gyroscope and accelerometer), IMU calibration.
 * [`rc.ino`](../flix/rc.ino) — reading data from the RC receiver, RC calibration.
-* [`estimate.ino`](../flix/estimate.ino) — drone's attitude estimation, complementary filter.
-* [`control.ino`](../flix/control.ino) — drone's attitude and rates control, three-dimensional two-level cascade PID controller.
-* [`motors.ino`](../flix/motors.ino) — PWM motor outputs control.
+* [`estimate.ino`](../flix/estimate.ino) — attitude estimation, complementary filter.
+* [`control.ino`](../flix/control.ino) — control subsystem, three-dimensional two-level cascade PID controller.
+* [`motors.ino`](../flix/motors.ino) — PWM motor output control.
+* [`mavlink.ino`](../flix/mavlink.ino) — interaction with QGroundControl or [pyflix](../tools/pyflix) via MAVLink protocol.
 
-Utility files include:
+Utility files:
 
-* [`vector.h`](../flix/vector.h), [`quaternion.h`](../flix/quaternion.h) — project's vector and quaternion libraries implementation.
-* [`pid.h`](../flix/pid.h) — generic PID controller implementation.
-* [`lpf.h`](../flix/lpf.h) — generic low-pass filter implementation.
+* [`vector.h`](../flix/vector.h), [`quaternion.h`](../flix/quaternion.h) — vector and quaternion libraries.
+* [`pid.h`](../flix/pid.h) — generic PID controller.
+* [`lpf.h`](../flix/lpf.h) — generic low-pass filter.
+
+### Control subsystem
+
+Pilot inputs are interpreted in `interpretControls()`, and then converted to the *control command*, which consists of the following:
+
+* `attitudeTarget` *(Quaternion)* — target attitude of the drone.
+* `ratesTarget` *(Vector)* — target angular rates, *rad/s*.
+* `ratesExtra` *(Vector)* — additional (feed-forward) angular rates , used for yaw rate control in STAB mode, *rad/s*.
+* `torqueTarget` *(Vector)* — target torque, range [-1, 1].
+* `thrustTarget` *(float)* — collective thrust target, range [0, 1].
+
+Control command is processed in `controlAttitude()`, `controlRates()`, `controlTorque()` functions. Each function may be skipped if the corresponding target is set to `NAN`.
+
+<img src="img/control.svg" width=300 alt="Control subsystem diagram">
+
+Armed state is stored in `armed` variable, and current mode is stored in `mode` variable.
 
 ## Building
 
-See build instructions in [build.md](build.md).
+See build instructions in [usage.md](usage.md).

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+        <line class="c" x1="347" y1="420.2" x2="347" y2="61.78"/>
+        <polygon class="d" points="370.34 68.61 347 28.2 323.66 68.61 370.34 68.61"/>
+      </g>
+    </g>
+    <g class="b">
+      <g>
+        <line class="e" x1="347" y1="420.2" x2="29.31" y2="597.81"/>
+        <polygon class="f" points="23.89 574.11 0 614.2 46.66 614.84 23.89 574.11"/>
+      </g>
+    </g>
+    <g class="b">
+      <g>
+        <line class="g" x1="347" y1="420.2" x2="503.22" y2="501.67"/>
+        <polygon class="h" points="486.38 519.2 533 517.2 507.96 477.82 486.38 519.2"/>
+      </g>
+    </g>
+    <text class="a" transform="translate(58.06 635.89)">y</text>
+  </g>
+</svg>

docs/img/right-axes.svg

@@ -0,0 +1,67 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 533 646.91">
+  <defs>
+    <style>
+      .a {
+        opacity: 0.8;
+      }
+
+      .b, .d, .f {
+        fill: none;
+        stroke-linejoin: bevel;
+        stroke-width: 13px;
+      }
+
+      .b {
+        stroke: #57ed00;
+      }
+
+      .c {
+        fill: #57ed00;
+      }
+
+      .d {
+        stroke: #d80100;
+      }
+
+      .e {
+        fill: #d80100;
+      }
+
+      .f {
+        stroke: #0076ba;
+      }
+
+      .g {
+        fill: #0076ba;
+      }
+
+      .h {
+        font-size: 50px;
+        font-family: Tahoma;
+      }
+    </style>
+  </defs>
+  <g>
+    <g class="a">
+      <g>
+        <line class="b" x1="347" y1="420.2" x2="503.22" y2="501.67"/>
+        <polygon class="c" points="486.38 519.2 533 517.2 507.96 477.82 486.38 519.2"/>
+      </g>
+    </g>
+    <g class="a">
+      <g>
+        <line class="d" x1="347" y1="420.2" x2="29.31" y2="597.81"/>
+        <polygon class="e" points="23.89 574.11 0 614.2 46.66 614.84 23.89 574.11"/>
+      </g>
+    </g>
+    <g class="a">
+      <g>
+        <line class="f" x1="347" y1="420.2" x2="347" y2="61.78"/>
+        <polygon class="g" points="370.34 68.61 347 28.2 323.66 68.61 370.34 68.61"/>
+      </g>
+    </g>
+    <text class="h" transform="translate(58.62 636.12)">x</text>
+    <text class="h" transform="translate(505.06 562.18)">y</text>
+    <text class="h" transform="translate(370.06 43.18)">z</text>
+  </g>
+</svg>

docs/rotation.css

@@ -0,0 +1,29 @@
+.diagram svg {
+	display: block;
+	width: 100%;
+	height: 400px;
+}
+.diagram .label {
+	font-family: Arial, sans-serif;
+	font-size: 20px;
+	pointer-events: none;
+	color: black;
+	opacity: 0.8;
+	user-select: none;
+}
+.diagram label {
+	display: block;
+}
+@media (min-width: 800px) {
+	.diagram b {
+		width: 200px;
+		display: inline-block;
+	}
+}
+.diagram p.quaternion {
+	overflow-x: auto;
+}
+.diagram input {
+	text-align: center;
+	width: 100%;
+}

docs/theme/index.hbs

@@ -118,7 +118,7 @@
                     <a href="https://t.me/opensourcequadcopter" class="telegram">Telegram-канал</a>
                     💰 Поддержать проект:
                     <iframe style="margin-top: 0.4em;" src="https://yoomoney.ru/quickpay/fundraise/button?billNumber=16U9OH2S4IT.241205&" width="330" height="50" frameborder="0" allowtransparency="true" scrolling="no"></iframe>​
-                    &copy; 2024 Олег Калачев
+                    &copy; 2025 Олег Калачев
                 </footer>
             </mdbook-sidebar-scrollbox>
             <noscript>

docs/troubleshooting.md

@@ -4,8 +4,9 @@
 
 Do the following:
 
-* **Check ESP32 core is installed**. Check if the version matches the one used in the [tutorial](build.md#firmware).
+* **Check ESP32 core is installed**. Check if the version matches the one used in the [tutorial](usage.md#firmware).
 * **Check libraries**. Install all the required libraries from the tutorial. Make sure there are no MPU9250 or other peripherals libraries that may conflict with the ones used in the tutorial.
+* **Check the chosen board**. The correct board to choose in Arduino IDE for ESP32 Mini is *WEMOS D1 MINI ESP32*.
 
 ## The drone doesn't fly
 
@@ -13,10 +14,11 @@ Do the following:
 
 * **Check the battery voltage**. Use a multimeter to measure the battery voltage. It should be in range of 3.7-4.2 V.
 * **Check if there are some startup errors**. Connect the ESP32 to the computer and check the Serial Monitor output. Use the Reset button to make sure you see the whole ESP32 output.
-* **Make sure correct IMU model is chosen**. If using ICM-20948 board, change `MPU9250` to `ICM20948` everywhere in the `imu.ino` file.
+* **Check the baudrate is correct**. If you see garbage characters in the Serial Monitor, make sure the baudrate is set to 115200.
+* **Make sure correct IMU model is chosen**. If using ICM-20948/MPU-6050 board, change `MPU9250` to `ICM20948`/`MPU6050` in the `imu.ino` file.
 * **Check if the CLI is working**. Perform `help` command in Serial Monitor. You should see the list of available commands. You can also access the CLI using QGroundControl (*Vehicle Setup* ⇒ *Analyze Tools* ⇒ *MAVLink Console*).
 * **Configure QGroundControl correctly before connecting to the drone** if you use it to control the drone. Go to the settings and enable *Virtual Joystick*. *Auto-Center Throttle* setting **should be disabled**.
-* **Make sure you're not moving the drone several seconds after the power on**. The drone calibrates its gyroscope on the start so it should stay still for a while.
+* **If QGroundControl doesn't connect**, you might need to disable the firewall and/or VPN on your computer.
 * **Check the IMU is working**. Perform `imu` command and check its output:
   * The `status` field should be `OK`.
   * The `rate` field should be about 1000 (Hz).
@@ -30,7 +32,6 @@ Do the following:
   * `mfl` — should rotate front left motor (clockwise).
   * `mrl` — should rotate rear left motor (counter-clockwise).
   * `mrr` — should rotate rear right motor (clockwise).
-* **Calibrate the RC** if you use it. Type `cr` command in Serial Monitor and follow the instructions.
-* **Check the RC data** if you use it. Use `rc` command, `Control` should show correct values between -1 and 1, and between 0 and 1 for the throttle.
+* **Check the remote control**. Using `rc` command, check the control values reflect your sticks movement. All the controls should change between -1 and 1, and throttle between 0 and 1.
+* If using SBUS receiver, **calibrate the RC**. Type `cr` command in Serial Monitor and follow the instructions.
 * **Check the IMU output using QGroundControl**. Connect to the drone using QGroundControl on your computer. Go to the *Analyze* tab, *MAVLINK Inspector*. Plot the data from the `SCALED_IMU` message. The gyroscope and accelerometer data should change according to the drone movement.
-* **Check the gyroscope only attitude estimation**. Comment out `applyAcc();` line in `estimate.ino` and check if the attitude estimation in QGroundControl. It should be stable, but only drift very slowly.

docs/usage.md

@@ -0,0 +1,252 @@
+# Usage: build, setup and flight
+
+To use Flix, you need to build the firmware and upload it to the ESP32 board. For simulation, you need to build and run the simulator.
+
+For the start, clone the repository using git:
+
+```bash
+git clone https://github.com/okalachev/flix.git
+cd flix
+```
+
+## Simulation
+
+### Ubuntu
+
+The latest version of Ubuntu supported by Gazebo 11 simulator is 20.04. If you have a newer version, consider using a virtual machine.
+
+1. Install Arduino CLI:
+
+   ```bash
+   curl -fsSL https://raw.githubusercontent.com/arduino/arduino-cli/master/install.sh | BINDIR=~/.local/bin sh
+   ```
+
+2. Install Gazebo 11:
+
+   ```bash
+   sudo sh -c 'echo "deb http://packages.osrfoundation.org/gazebo/ubuntu-stable `lsb_release -cs` main" > /etc/apt/sources.list.d/gazebo-stable.list'
+   wget https://packages.osrfoundation.org/gazebo.key -O - | sudo apt-key add -
+   sudo apt-get update
+   sudo apt-get install -y gazebo11 libgazebo11-dev
+   ```
+
+   Set up your Gazebo environment variables:
+
+   ```bash
+   echo "source /usr/share/gazebo/setup.sh" >> ~/.bashrc
+   source ~/.bashrc
+   ```
+
+3. Install SDL2 and other dependencies:
+
+   ```bash
+   sudo apt-get update && sudo apt-get install build-essential libsdl2-dev
+   ```
+
+4. Add your user to the `input` group to enable joystick support (you need to re-login after this command):
+
+   ```bash
+   sudo usermod -a -G input $USER
+   ```
+
+5. Run the simulation:
+
+   ```bash
+   make simulator
+   ```
+
+### macOS
+
+1. Install Homebrew package manager, if you don't have it installed:
+
+   ```bash
+   /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"
+   ```
+
+2. Install Arduino CLI, Gazebo 11 and SDL2:
+
+   ```bash
+   brew tap osrf/simulation
+   brew install arduino-cli
+   brew install gazebo11
+   brew install sdl2
+   ```
+
+   Set up your Gazebo environment variables:
+
+   ```bash
+   echo "source /opt/homebrew/share/gazebo/setup.sh" >> ~/.zshrc
+   source ~/.zshrc
+   ```
+
+3. Run the simulation:
+
+   ```bash
+   make simulator
+   ```
+
+### Setup
+
+#### Control with smartphone
+
+1. Install [QGroundControl mobile app](https://docs.qgroundcontrol.com/master/en/qgc-user-guide/getting_started/download_and_install.html#android) on your smartphone. For **iOS**, use [QGroundControl build from TAJISOFT](https://apps.apple.com/ru/app/qgc-from-tajisoft/id1618653051).
+2. Connect your smartphone to the same Wi-Fi network as the machine running the simulator.
+3. If you're using a virtual machine, make sure that its network is set to the **bridged** mode with Wi-Fi adapter selected.
+4. Run the simulation.
+5. Open QGroundControl app. It should connect and begin showing the virtual drone's telemetry automatically.
+6. Go to the settings and enable *Virtual Joystick*. *Auto-Center Throttle* setting **should be disabled**.
+7. Use the virtual joystick to fly the drone!
+
+#### Control with USB remote control
+
+1. Connect your USB remote control to the machine running the simulator.
+2. Run the simulation.
+3. Calibrate the RC using `cr` command in the command line interface.
+4. Run the simulation again.
+5. Use the USB remote control to fly the drone!
+
+## Firmware
+
+### Arduino IDE (Windows, Linux, macOS)
+
+1. Install [Arduino IDE](https://www.arduino.cc/en/software) (version 2 is recommended).
+2. Windows users might need to install [USB to UART bridge driver from Silicon Labs](https://www.silabs.com/developers/usb-to-uart-bridge-vcp-drivers).
+3. Install ESP32 core, version 3.2.0. See the [official Espressif's instructions](https://docs.espressif.com/projects/arduino-esp32/en/latest/installing.html#installing-using-arduino-ide) on installing ESP32 Core in Arduino IDE.
+4. Install the following libraries using [Library Manager](https://docs.arduino.cc/software/ide-v2/tutorials/ide-v2-installing-a-library):
+   * `FlixPeriph`, the latest version.
+   * `MAVLink`, version 2.0.16.
+5. Clone the project using git or [download the source code as a ZIP archive](https://codeload.github.com/okalachev/flix/zip/refs/heads/master).
+6. Open the downloaded Arduino sketch `flix/flix.ino` in Arduino IDE.
+7. Connect your ESP32 board to the computer and choose correct board type in Arduino IDE (*WEMOS D1 MINI ESP32* for ESP32 Mini) and the port.
+8. [Build and upload](https://docs.arduino.cc/software/ide-v2/tutorials/getting-started/ide-v2-uploading-a-sketch) the firmware using Arduino IDE.
+
+### Command line (Windows, Linux, macOS)
+
+1. [Install Arduino CLI](https://arduino.github.io/arduino-cli/installation/).
+
+   On Linux, use:
+
+   ```bash
+   curl -fsSL https://raw.githubusercontent.com/arduino/arduino-cli/master/install.sh | BINDIR=~/.local/bin sh
+   ```
+
+2. Windows users might need to install [USB to UART bridge driver from Silicon Labs](https://www.silabs.com/developers/usb-to-uart-bridge-vcp-drivers).
+3. Compile the firmware using `make`. Arduino dependencies will be installed automatically:
+
+   ```bash
+   make
+   ```
+
+   You can flash the firmware to the board using command:
+
+   ```bash
+   make upload
+   ```
+
+   You can also compile the firmware, upload it and start serial port monitoring using command:
+
+   ```bash
+   make upload monitor
+   ```
+
+See other available Make commands in the [Makefile](../Makefile).
+
+> [!TIP]
+> You can test the firmware on a bare ESP32 board without connecting IMU and other peripherals. The Wi-Fi network `flix` should appear and all the basic functionality including CLI and QGroundControl connection should work.
+
+### Setup
+
+Before flight you need to calibrate the accelerometer:
+
+1. Open Serial Monitor in Arduino IDE (or use `make monitor` command in the command line).
+2. Type `ca` command there and follow the instructions.
+
+#### Control with smartphone
+
+1. Install [QGroundControl mobile app](https://docs.qgroundcontrol.com/master/en/qgc-user-guide/getting_started/download_and_install.html#android) on your smartphone.
+2. Power the drone using the battery.
+3. Connect your smartphone to the appeared `flix` Wi-Fi network (password: `flixwifi`).
+4. Open QGroundControl app. It should connect and begin showing the drone's telemetry automatically.
+5. Go to the settings and enable *Virtual Joystick*. *Auto-Center Throttle* setting **should be disabled**.
+6. Use the virtual joystick to fly the drone!
+
+> [!TIP]
+> Decrease `TILT_MAX` parameter when flying using the smartphone to make the controls less sensitive.
+
+#### Control with remote control
+
+Before flight using remote control, you need to calibrate it:
+
+1. Open Serial Monitor in Arduino IDE (or use `make monitor` command in the command line).
+2. Type `cr` command there and follow the instructions.
+3. Use the remote control to fly the drone!
+
+#### Control with USB remote control (Wi-Fi)
+
+If your drone doesn't have RC receiver installed, you can use USB remote control and QGroundControl app to fly it.
+
+1. Install [QGroundControl](https://docs.qgroundcontrol.com/master/en/qgc-user-guide/getting_started/download_and_install.html) app on your computer.
+2. Connect your USB remote control to the computer.
+3. Power up the drone.
+4. Connect your computer to the appeared `flix` Wi-Fi network (password: `flixwifi`).
+5. Launch QGroundControl app. It should connect and begin showing the drone's telemetry automatically.
+6. Go the the QGroundControl menu ⇒ *Vehicle Setup* ⇒ *Joystick*. Calibrate you USB remote control there.
+7. Use the USB remote control to fly the drone!
+
+> [!NOTE]
+> If something goes wrong, go to the [Troubleshooting](troubleshooting.md) article.
+
+## Flight
+
+For both virtual sticks and a physical joystick, the default control scheme is left stick for throttle and yaw and right stick for pitch and roll:
+
+<img src="img/controls.svg" width="300">
+
+### Arming and disarming
+
+To start the motors, you should **arm** the drone. To do that, move the left stick to the bottom right corner:
+
+<img src="img/arming.svg" width="150">
+
+After that, the motors **will start spinning** at low speed, indicating that the drone is armed and ready to fly.
+
+When finished flying, **disarm** the drone, moving the left stick to the bottom left corner:
+
+<img src="img/disarming.svg" width="150">
+
+### Flight modes
+
+Flight mode is changed using mode switch on the remote control or using the command line.
+
+#### STAB
+
+The default mode is *STAB*. In this mode, the drone stabilizes its attitude (orientation). The left stick controls throttle and yaw rate, the right stick controls pitch and roll angles.
+
+> [!IMPORTANT]
+> The drone doesn't stabilize its position, so slight drift is possible. The pilot should compensate it manually.
+
+#### ACRO
+
+In this mode, the pilot controls the angular rates. This control method is difficult to fly and mostly used in FPV racing.
+
+#### MANUAL
+
+Manual mode disables all the stabilization, and the pilot inputs are passed directly to the motors. This mode is intended for testing and demonstration purposes only, and basically the drone **cannot fly in this mode**.
+
+#### AUTO
+
+In this mode, the pilot inputs are ignored (except the mode switch, if configured). The drone can be controlled using [pyflix](../tools/pyflix/) Python library, or by modifying the firmware to implement the needed autonomous behavior.
+
+If the pilot moves the control sticks, the drone will switch back to *STAB* mode.
+
+## Adjusting parameters
+
+You can adjust some of the drone's parameters (include PID coefficients) in QGroundControl app. In order to do that, go to the QGroundControl menu ⇒ *Vehicle Setup* ⇒ *Parameters*.
+
+<img src="img/parameters.png" width="400">
+
+## CLI access
+
+In addition to accessing the drone's command line interface (CLI) using the serial port, you can also access it with QGroundControl using Wi-Fi connection. To do that, go to the QGroundControl menu ⇒ *Vehicle Setup* ⇒ *Analyze Tools* ⇒ *MAVLink Console*.
+
+<img src="img/cli.png" width="400">

docs/user.md

@@ -4,6 +4,62 @@ This page contains user-built drones based on the Flix project. Publish your pro
 
 ---
 
+## RoboCamp
+
+Author: RoboCamp participants.<br>
+Description: 3D-printed and wooden frames, ESP32 Mini, DC-DC buck-boost converters. BetaFPV LiteRadio 3 to control the drones via Wi-Fi connection.<br>
+Features: altitude hold, obstacle avoidance, autonomous flight elements.<br>
+Some of the designed model files: https://drive.google.com/drive/folders/18YHWGquKeIevzrMH4-OUT-zKXMETTEUu?usp=share_link.
+
+RoboCamp took place in July 2025, Saint Petersburg, where 9 participants designed and built their own drones using the Flix project, and then modified the firmware to complete specific flight tasks.
+
+See the detailed video about the event:
+
+<a href="https://youtu.be/Wd3yaorjTx0"><img width=500 src="https://img.youtube.com/vi/Wd3yaorjTx0/sddefault.jpg"></a>
+
+Built drones:
+
+<img src="img/user/robocamp/1.jpg" width=500>
+
+---
+
+Author: chkroko.<br>
+Description: the first Flix drone built with **brushless motors** (DShot interface).<br>
+Features: SpeedyBee BLS 35A Mini V2 ESC, ESP32-S3 board, EMAX ECO 2 2207 1700kv motors, ICM20948V2 IMU, INA226 power monitor and Bluetooth gamepad for control.<br>
+Patch for DShot ESC: https://github.com/Krokodilushka/flix/commit/568345a45ca7ed5b458a11a9d0a9f4c8a91e70ac.
+
+**Flight video:**
+
+<a href="https://drive.google.com/file/d/1GFRanASxKmXINi70fxS5RuzV3LJp7f3m/view?usp=share_link"><img height=300 src="img/user/chkroko-bldc/video.jpg"></a>
+
+<img src="img/user/chkroko-bldc/1.jpg" height=150> <img src="img/user/chkroko-bldc/2.jpg" height=150> <img src="img/user/chkroko-bldc/3.jpg" height=150>
+
+---
+
+Author: chkroko.<br>
+Modification: Control using Bluetooth with **Flydigi Vader 3** gamepad. Source code: https://github.com/Krokodilushka/flix/tree/dev.<br>
+Features: ESP32-C3 SuperMini, BMP580 barometer, INA226 power monitor, IRLZ44N MOSFETs.<br>
+Full description: https://telegra.ph/Flix-dron-06-13.
+
+**Flight video:**
+
+<a href="https://drive.google.com/file/d/1orVKA_-gsezDTns2Xt8xW1BCWPcyPitR/view?usp=sharing"><img height=300 src="img/user/chkroko/video.jpg"></a>
+
+<img src="img/user/chkroko/1.jpg" height=150> <img src="img/user/chkroko/2.jpg" height=150>
+
+---
+
+Author: chkroko.<br>
+Features: ESP32-C3 SuperMini board, INA226 power monitor, IRLZ44N MOSFETs, MPU-6500 IMU.
+
+**Flight video:**
+
+<a href="https://drive.google.com/file/d/1-4ciDsj8slTEaxxRl1-QAkx0cUDkb8iy/view?usp=sharing"><img height=300 src="img/user/cryptokobans/video.jpg"></a>
+
+<img src="img/user/cryptokobans/1.jpg" height=150> <img src="img/user/cryptokobans/2.jpg" height=150>
+
+---
+
 Author: [@jeka_chex](https://t.me/jeka_chex).<br>
 Features: custom frame, FPV camera, 3-blade 31 mm propellers.<br>
 Motor drivers: AON7410 MOSFET + capacitors.<br>
@@ -17,27 +73,14 @@ Custom frame files: https://drive.google.com/drive/folders/1QCIc-_YYFxJN4cMhVLjL
 
 <a href="https://drive.google.com/file/d/1RSU6VWs9omsge4hGloH5NQqnxvLyhMKB/view?usp=sharing"><img height=300 src="img/user/jeka_chex/video-fpv.jpg"></a>
 
-<table>
-	<tr>
-		<td><img src="img/user/jeka_chex/1.jpg" height=150></td>
-		<td><img src="img/user/jeka_chex/2.jpg" height=150></td>
-		<td><img src="img/user/jeka_chex/3.jpg" height=150></td>
-		<td><img src="img/user/jeka_chex/4.jpg" height=150></td>
-		<td><img src="img/user/jeka_chex/5.jpg" height=150></td>
-	</tr>
-</table>
+<img src="img/user/jeka_chex/1.jpg" height=150> <img src="img/user/jeka_chex/2.jpg" height=150> <img src="img/user/jeka_chex/3.jpg" height=150> <img src="img/user/jeka_chex/4.jpg" height=150> <img src="img/user/jeka_chex/5.jpg" height=150>
 
 ---
 
 Author: [@fisheyeu](https://t.me/fisheyeu).<br>
 [Video](https://drive.google.com/file/d/1IT4eMmWPZpmaZR_qsIRmNJ52hYkFB_0q/view?usp=share_link).
 
-<table>
-	<tr>
-		<td><img src="img/user/fisheyeu/1.jpg" height=300></td>
-		<td><img src="img/user/fisheyeu/2.jpg" height=300></td>
-	</tr>
-</table>
+<img src="img/user/fisheyeu/1.jpg" height=300> <img src="img/user/fisheyeu/2.jpg" height=300>
 
 ---
 
@@ -46,13 +89,7 @@ Custom propellers guard 3D-model: https://drive.google.com/file/d/1TKnzwvrZYzYuR
 Features: ESP32-C3 microcontroller is used.<br>
 [Video](https://drive.google.com/file/d/1B0NMcsk0fgwUgNr9XuLOdR2yYCuaj008/view?usp=share_link).
 
-<table>
-	<tr>
-		<td><img src="img/user/p_kabakov/1.jpg" width=150></td>
-		<td><img src="img/user/p_kabakov/2.jpg" width=150></td>
-		<td><img src="img/user/p_kabakov/3.jpg" width=150></td>
-	</tr>
-</table>
+<img src="img/user/p_kabakov/1.jpg" width=150> <img src="img/user/p_kabakov/2.jpg" width=150> <img src="img/user/p_kabakov/3.jpg" width=150>
 
 **Custom Wi-Fi RC control:**
 
@@ -65,12 +102,7 @@ See source and description (in Russian): https://github.com/pavelkabakov/flix/tr
 Author: [@yi_lun](https://t.me/yi_lun).<br>
 [Video](https://drive.google.com/file/d/1TkSuvHQ_0qQPFUpY5XjJzmhnpX_07cTg/view?usp=share_link).
 
-<table>
-	<tr>
-		<td><img src="img/user/yi_lun/1.jpg" width=300></td>
-		<td><img src="img/user/yi_lun/2.jpg" width=300></td>
-	</tr>
-</table>
+<img src="img/user/yi_lun/1.jpg" width=300> <img src="img/user/yi_lun/2.jpg" width=300>
 
 ---
 
@@ -81,12 +113,7 @@ Schematics: https://miro.com/app/board/uXjVN-dTjoo=/?moveToWidget=34587646121795
 
 <a href="https://www.youtube.com/watch?v=wi4w_hOmKcQ"><img width=500 src="img/user/peter_ukhov-2/video.jpg"></a>
 
-<table>
-	<tr>
-		<td><img src="img/user/peter_ukhov-2/1.jpg" width=300></td>
-		<td><img src="img/user/peter_ukhov-2/2.jpg" width=300></td>
-	</tr>
-</table>
+<img src="img/user/peter_ukhov-2/1.jpg" width=300> <img src="img/user/peter_ukhov-2/2.jpg" width=300>
 
 ---
 
@@ -95,15 +122,7 @@ Files for 3D printing of the custom frame: https://drive.google.com/file/d/1tkNm
 
 <a href="https://t.me/opensourcequadcopter/61"><img width=500 src="img/user/alexey_karakash/video.jpg"></a>
 
-<table>
-	<tr>
-		<td><img src="img/user/alexey_karakash/1.jpg" height=150></td>
-		<td><img src="img/user/alexey_karakash/2.jpg" height=150></td>
-		<td><img src="img/user/alexey_karakash/3.jpg" height=150></td>
-		<td><img src="img/user/alexey_karakash/4.jpg" height=150></td>
-		<td><img src="img/user/alexey_karakash/5.jpg" height=150></td>
-	</tr>
-</table>
+<img src="img/user/alexey_karakash/1.jpg" height=150> <img src="img/user/alexey_karakash/2.jpg" height=150> <img src="img/user/alexey_karakash/3.jpg" height=150> <img src="img/user/alexey_karakash/4.jpg" height=150> <img src="img/user/alexey_karakash/5.jpg" height=150>
 
 ---
 
@@ -111,13 +130,7 @@ Author: [@rudpa](https://t.me/rudpa).<br>
 
 <a href="https://t.me/opensourcequadcopter/46"><img width=500 src="img/user/rudpa/video.jpg"></a>
 
-<table>
-	<tr>
-		<td><img src="img/user/rudpa/1.jpg" height=150></td>
-		<td><img src="img/user/rudpa/2.jpg" height=150></td>
-		<td><img src="img/user/rudpa/3.jpg" height=150></td>
-	</tr>
-</table>
+<img src="img/user/rudpa/1.jpg" height=150> <img src="img/user/rudpa/2.jpg" height=150> <img src="img/user/rudpa/3.jpg" height=150>
 
 ---
 
@@ -126,10 +139,4 @@ Schematics: https://miro.com/app/board/uXjVN-dTjoo=/?moveToWidget=34587646123382
 
 <a href="https://t.me/opensourcequadcopter/24"><img width=500 src="img/user/peter_ukhov/video.jpg"></a>
 
-<table>
-	<tr>
-		<td><img src="img/user/peter_ukhov/1.jpg" height=150></td>
-		<td><img src="img/user/peter_ukhov/2.jpg" height=150></td>
-		<td><img src="img/user/peter_ukhov/3.jpg" height=150></td>
-	</tr>
-</table>
+<img src="img/user/peter_ukhov/1.jpg" height=150> <img src="img/user/peter_ukhov/2.jpg" height=150> <img src="img/user/peter_ukhov/3.jpg" height=150>

flix/cli.ino

@@ -8,9 +8,12 @@
 #include "util.h"
 
 extern const int MOTOR_REAR_LEFT, MOTOR_REAR_RIGHT, MOTOR_FRONT_RIGHT, MOTOR_FRONT_LEFT;
-extern float loopRate, dt;
-extern double t;
-extern int rollChannel, pitchChannel, throttleChannel, yawChannel, armedChannel, modeChannel;
+extern const int ACRO, STAB, AUTO;
+extern float t, dt, loopRate;
+extern uint16_t channels[16];
+extern float controlRoll, controlPitch, controlThrottle, controlYaw, controlMode;
+extern int mode;
+extern bool armed;
 
 const char* motd =
 "\nWelcome to\n"
@@ -30,13 +33,16 @@ const char* motd =
 "ps - show pitch/roll/yaw\n"
 "psq - show attitude quaternion\n"
 "imu - show IMU data\n"
+"arm - arm the drone\n"
+"disarm - disarm the drone\n"
+"stab/acro/auto - set mode\n"
 "rc - show RC data\n"
 "mot - show motor output\n"
 "log - dump in-RAM log\n"
 "cr - calibrate RC\n"
-"cg - calibrate gyro\n"
 "ca - calibrate accel\n"
 "mfr, mfl, mrr, mrl - test motor (remove props)\n"
+"sys - show system info\n"
 "reset - reset drone's state\n"
 "reboot - reboot the drone\n";
 
@@ -53,31 +59,30 @@ void print(const char* format, ...) {
 }
 
 void pause(float duration) {
-#if ARDUINO
-	double start = t;
+	float start = t;
 	while (t - start < duration) {
 		step();
 		handleInput();
 #if WIFI_ENABLED
 		processMavlink();
 #endif
+		delay(50);
 	}
-#else
-	// Code above won't work in the simulation
-	delay(duration * 1000);
-#endif
 }
 
 void doCommand(String str, bool echo = false) {
 	// parse command
 	String command, arg0, arg1;
 	splitString(str, command, arg0, arg1);
+	if (command.isEmpty()) return;
 
 	// echo command
-	if (echo && !command.isEmpty()) {
+	if (echo) {
 		print("> %s\n", str.c_str());
 	}
 
+	command.toLowerCase();
+
 	// execute command
 	if (command == "help" || command == "motd") {
 		print("%s\n", motd);
@@ -96,36 +101,43 @@ void doCommand(String str, bool echo = false) {
 		resetParameters();
 	} else if (command == "time") {
 		print("Time: %f\n", t);
-		print("Loop rate: %f\n", loopRate);
+		print("Loop rate: %.0f\n", loopRate);
 		print("dt: %f\n", dt);
 	} else if (command == "ps") {
-		Vector a = attitude.toEulerZYX();
+		Vector a = attitude.toEuler();
 		print("roll: %f pitch: %f yaw: %f\n", degrees(a.x), degrees(a.y), degrees(a.z));
 	} else if (command == "psq") {
-		print("qx: %f qy: %f qz: %f qw: %f\n", attitude.x, attitude.y, attitude.z, attitude.w);
+		print("qw: %f qx: %f qy: %f qz: %f\n", attitude.w, attitude.x, attitude.y, attitude.z);
 	} else if (command == "imu") {
 		printIMUInfo();
-		print("gyro: %f %f %f\n", rates.x, rates.y, rates.z);
-		print("acc: %f %f %f\n", acc.x, acc.y, acc.z);
-		printIMUCal();
-		print("rate: %f\n", loopRate);
+		printIMUCalibration();
+		print("landed: %d\n", landed);
+	} else if (command == "arm") {
+		armed = true;
+	} else if (command == "disarm") {
+		armed = false;
+	} else if (command == "stab") {
+		mode = STAB;
+	} else if (command == "acro") {
+		mode = ACRO;
+	} else if (command == "auto") {
+		mode = AUTO;
 	} else if (command == "rc") {
-		print("Raw: throttle %d yaw %d pitch %d roll %d armed %d mode %d\n",
-			channels[throttleChannel], channels[yawChannel], channels[pitchChannel],
-			channels[rollChannel], channels[armedChannel], channels[modeChannel]);
-		print("Control: throttle %g yaw %g pitch %g roll %g armed %g mode %g\n",
-			controls[throttleChannel], controls[yawChannel], controls[pitchChannel],
-			controls[rollChannel], controls[armedChannel], controls[modeChannel]);
-		print("Mode: %s\n", getModeName());
+		print("channels: ");
+		for (int i = 0; i < 16; i++) {
+			print("%u ", channels[i]);
+		}
+		print("\nroll: %g pitch: %g yaw: %g throttle: %g mode: %g\n",
+			controlRoll, controlPitch, controlYaw, controlThrottle, controlMode);
+		print("mode: %s\n", getModeName());
+		print("armed: %d\n", armed);
 	} else if (command == "mot") {
-		print("Motors: front-right %g front-left %g rear-right %g rear-left %g\n",
+		print("front-right %g front-left %g rear-right %g rear-left %g\n",
 			motors[MOTOR_FRONT_RIGHT], motors[MOTOR_FRONT_LEFT], motors[MOTOR_REAR_RIGHT], motors[MOTOR_REAR_LEFT]);
 	} else if (command == "log") {
 		dumpLog();
 	} else if (command == "cr") {
 		calibrateRC();
-	} else if (command == "cg") {
-		calibrateGyro();
 	} else if (command == "ca") {
 		calibrateAccel();
 	} else if (command == "mfr") {
@@ -136,12 +148,29 @@ void doCommand(String str, bool echo = false) {
 		testMotor(MOTOR_REAR_RIGHT);
 	} else if (command == "mrl") {
 		testMotor(MOTOR_REAR_LEFT);
+	} else if (command == "sys") {
+#ifdef ESP32
+		print("Chip: %s\n", ESP.getChipModel());
+		print("Temperature: %.1f °C\n", temperatureRead());
+		print("Free heap: %d\n", ESP.getFreeHeap());
+		// Print tasks table
+		print("Num  Task                Stack  Prio  Core  CPU%%\n");
+		int taskCount = uxTaskGetNumberOfTasks();
+		TaskStatus_t *systemState = new TaskStatus_t[taskCount];
+		uint32_t totalRunTime;
+		uxTaskGetSystemState(systemState, taskCount, &totalRunTime);
+		for (int i = 0; i < taskCount; i++) {
+			String core = systemState[i].xCoreID == tskNO_AFFINITY ? "*" : String(systemState[i].xCoreID);
+			int cpuPercentage = systemState[i].ulRunTimeCounter / (totalRunTime / 100);
+			print("%-5d%-20s%-7d%-6d%-6s%d\n",systemState[i].xTaskNumber, systemState[i].pcTaskName,
+				systemState[i].usStackHighWaterMark, systemState[i].uxCurrentPriority, core, cpuPercentage);
+		}
+		delete[] systemState;
+#endif
 	} else if (command == "reset") {
 		attitude = Quaternion();
 	} else if (command == "reboot") {
 		ESP.restart();
-	} else if (command == "") {
-		// do nothing
 	} else {
 		print("Invalid command: %s\n", command.c_str());
 	}

flix/control.ino

@@ -21,7 +21,7 @@
 #define YAWRATE_I 0.0
 #define YAWRATE_D 0.0
 #define YAWRATE_I_LIM 0.3
-#define ROLL_P 4.5
+#define ROLL_P 6
 #define ROLL_I 0
 #define ROLL_D 0
 #define PITCH_P ROLL_P
@@ -32,11 +32,10 @@
 #define ROLLRATE_MAX radians(360)
 #define YAWRATE_MAX radians(300)
 #define TILT_MAX radians(30)
-
 #define RATES_D_LPF_ALPHA 0.2 // cutoff frequency ~ 40 Hz
 
-enum { MANUAL, ACRO, STAB, USER } mode = STAB;
-enum { YAW, YAW_RATE } yawMode = YAW;
+const int MANUAL = 0, ACRO = 1, STAB = 2, AUTO = 3; // flight modes
+int mode = STAB;
 bool armed = false;
 
 PID rollRatePID(ROLLRATE_P, ROLLRATE_I, ROLLRATE_D, ROLLRATE_I_LIM, RATES_D_LPF_ALPHA);
@@ -50,111 +49,96 @@ float tiltMax = TILT_MAX;
 
 Quaternion attitudeTarget;
 Vector ratesTarget;
+Vector ratesExtra; // feedforward rates
 Vector torqueTarget;
 float thrustTarget;
 
 extern const int MOTOR_REAR_LEFT, MOTOR_REAR_RIGHT, MOTOR_FRONT_RIGHT, MOTOR_FRONT_LEFT;
-extern int rollChannel, pitchChannel, throttleChannel, yawChannel, armedChannel, modeChannel;
+extern float controlRoll, controlPitch, controlThrottle, controlYaw, controlMode;
 
 void control() {
-	interpretRC();
+	interpretControls();
 	failsafe();
-	if (mode == STAB) {
-		controlAttitude();
-		controlRate();
-		controlTorque();
-	} else if (mode == ACRO) {
-		controlRate();
-		controlTorque();
-	} else if (mode == MANUAL) {
-		controlTorque();
-	}
+	controlAttitude();
+	controlRates();
+	controlTorque();
 }
 
-void interpretRC() {
-	armed = controls[throttleChannel] >= 0.05 &&
-		(controls[armedChannel] >= 0.5 || isnan(controls[armedChannel])); // assume armed if armed channel is not defined
-
+void interpretControls() {
 	// NOTE: put ACRO or MANUAL modes there if you want to use them
-	if (controls[modeChannel] < 0.25) {
-		mode = STAB;
-	} else if (controls[modeChannel] < 0.75) {
-		mode = STAB;
-	} else {
-		mode = STAB;
-	}
+	if (controlMode < 0.25) mode = STAB;
+	if (controlMode < 0.75) mode = STAB;
+	if (controlMode > 0.75) mode = STAB;
 
-	thrustTarget = controls[throttleChannel];
+	if (mode == AUTO) return; // pilot is not effective in AUTO mode
+
+	if (controlThrottle < 0.05 && controlYaw > 0.95) armed = true; // arm gesture
+	if (controlThrottle < 0.05 && controlYaw < -0.95) armed = false; // disarm gesture
+
+	thrustTarget = controlThrottle;
+
+	if (mode == STAB) {
+		float yawTarget = attitudeTarget.getYaw();
+		if (!armed || invalid(yawTarget) || controlYaw != 0) yawTarget = attitude.getYaw(); // reset yaw target
+		attitudeTarget = Quaternion::fromEuler(Vector(controlRoll * tiltMax, controlPitch * tiltMax, yawTarget));
+		ratesExtra = Vector(0, 0, -controlYaw * maxRate.z); // positive yaw stick means clockwise rotation in FLU
+	}
 
 	if (mode == ACRO) {
-		yawMode = YAW_RATE;
-		ratesTarget.x = controls[rollChannel] * maxRate.x;
-		ratesTarget.y = controls[pitchChannel] * maxRate.y;
-		ratesTarget.z = -controls[yawChannel] * maxRate.z; // positive yaw stick means clockwise rotation in FLU
-
-	} else if (mode == STAB) {
-		yawMode = controls[yawChannel] == 0 ? YAW : YAW_RATE;
-
-		attitudeTarget = Quaternion::fromEulerZYX(Vector(
-			controls[rollChannel] * tiltMax,
-			controls[pitchChannel] * tiltMax,
-			attitudeTarget.getYaw()));
-		ratesTarget.z = -controls[yawChannel] * maxRate.z; // positive yaw stick means clockwise rotation in FLU
-
-	} else if (mode == MANUAL) {
-		// passthrough mode
-		yawMode = YAW_RATE;
-		torqueTarget = Vector(controls[rollChannel], controls[pitchChannel], -controls[yawChannel]) * 0.01;
+		attitudeTarget.invalidate(); // skip attitude control
+		ratesTarget.x = controlRoll * maxRate.x;
+		ratesTarget.y = controlPitch * maxRate.y;
+		ratesTarget.z = -controlYaw * maxRate.z; // positive yaw stick means clockwise rotation in FLU
 	}
 
-	if (yawMode == YAW_RATE || !motorsActive()) {
-		// update yaw target as we don't have control over the yaw
-		attitudeTarget.setYaw(attitude.getYaw());
+	if (mode == MANUAL) { // passthrough mode
+		attitudeTarget.invalidate(); // skip attitude control
+		ratesTarget.invalidate(); // skip rate control
+		torqueTarget = Vector(controlRoll, controlPitch, -controlYaw) * 0.01;
 	}
 }
 
 void controlAttitude() {
-	if (!armed) {
-		rollPID.reset();
-		pitchPID.reset();
-		yawPID.reset();
-		return;
-	}
+	if (!armed || attitudeTarget.invalid() || thrustTarget < 0.1) return; // skip attitude control
 
 	const Vector up(0, 0, 1);
-	Vector upActual = attitude.rotateVector(up);
-	Vector upTarget = attitudeTarget.rotateVector(up);
+	Vector upActual = Quaternion::rotateVector(up, attitude);
+	Vector upTarget = Quaternion::rotateVector(up, attitudeTarget);
 
-	Vector error = Vector::angularRatesBetweenVectors(upTarget, upActual);
+	Vector error = Vector::rotationVectorBetween(upTarget, upActual);
 
-	ratesTarget.x = rollPID.update(error.x, dt);
-	ratesTarget.y = pitchPID.update(error.y, dt);
+	ratesTarget.x = rollPID.update(error.x) + ratesExtra.x;
+	ratesTarget.y = pitchPID.update(error.y) + ratesExtra.y;
 
-	if (yawMode == YAW) {
-		float yawError = wrapAngle(attitudeTarget.getYaw() - attitude.getYaw());
-		ratesTarget.z = yawPID.update(yawError, dt);
-	}
+	float yawError = wrapAngle(attitudeTarget.getYaw() - attitude.getYaw());
+	ratesTarget.z = yawPID.update(yawError) + ratesExtra.z;
 }
 
-void controlRate() {
-	if (!armed) {
-		rollRatePID.reset();
-		pitchRatePID.reset();
-		yawRatePID.reset();
-		return;
-	}
+
+void controlRates() {
+	if (!armed || ratesTarget.invalid() || thrustTarget < 0.1) return; // skip rates control
 
 	Vector error = ratesTarget - rates;
 
 	// Calculate desired torque, where 0 - no torque, 1 - maximum possible torque
-	torqueTarget.x = rollRatePID.update(error.x, dt);
-	torqueTarget.y = pitchRatePID.update(error.y, dt);
-	torqueTarget.z = yawRatePID.update(error.z, dt);
+	torqueTarget.x = rollRatePID.update(error.x);
+	torqueTarget.y = pitchRatePID.update(error.y);
+	torqueTarget.z = yawRatePID.update(error.z);
 }
 
 void controlTorque() {
+	if (!torqueTarget.valid()) return; // skip torque control
+
 	if (!armed) {
-		memset(motors, 0, sizeof(motors));
+		memset(motors, 0, sizeof(motors)); // stop motors if disarmed
+		return;
+	}
+
+	if (thrustTarget < 0.1) {
+		motors[0] = 0.1; // idle thrust
+		motors[1] = 0.1;
+		motors[2] = 0.1;
+		motors[3] = 0.1;
 		return;
 	}
 
@@ -174,7 +158,7 @@ const char* getModeName() {
 		case MANUAL: return "MANUAL";
 		case ACRO: return "ACRO";
 		case STAB: return "STAB";
-		case USER: return "USER";
+		case AUTO: return "AUTO";
 		default: return "UNKNOWN";
 	}
 }

flix/estimate.ino

@@ -11,8 +11,6 @@
 #define WEIGHT_ACC 0.003
 #define RATES_LFP_ALPHA 0.2 // cutoff frequency ~ 40 Hz
 
-LowPassFilter<Vector> ratesFilter(RATES_LFP_ALPHA);
-
 void estimate() {
 	applyGyro();
 	applyAcc();
@@ -20,23 +18,24 @@ void estimate() {
 
 void applyGyro() {
 	// filter gyro to get angular rates
+	static LowPassFilter<Vector> ratesFilter(RATES_LFP_ALPHA);
 	rates = ratesFilter.update(gyro);
 
 	// apply rates to attitude
-	attitude = attitude.rotate(Quaternion::fromAngularRates(rates * dt));
+	attitude = Quaternion::rotate(attitude, Quaternion::fromRotationVector(rates * dt));
 }
 
 void applyAcc() {
 	// test should we apply accelerometer gravity correction
 	float accNorm = acc.norm();
-	bool landed = !motorsActive() && abs(accNorm - ONE_G) < ONE_G * 0.1f;
+	landed = !motorsActive() && abs(accNorm - ONE_G) < ONE_G * 0.1f;
 
 	if (!landed) return;
 
 	// calculate accelerometer correction
-	Vector up = attitude.rotateVector(Vector(0, 0, 1));
-	Vector correction = Vector::angularRatesBetweenVectors(acc, up) * WEIGHT_ACC;
+	Vector up = Quaternion::rotateVector(Vector(0, 0, 1), attitude);
+	Vector correction = Vector::rotationVectorBetween(acc, up) * WEIGHT_ACC;
 
 	// apply correction
-	attitude = attitude.rotate(Quaternion::fromAngularRates(correction));
+	attitude = Quaternion::rotate(attitude, Quaternion::fromRotationVector(correction));
 }

flix/failsafe.ino

@@ -1,41 +0,0 @@
-// Copyright (c) 2024 Oleg Kalachev <okalachev@gmail.com>
-// Repository: https://github.com/okalachev/flix
-
-// Fail-safe functions
-
-#define RC_LOSS_TIMEOUT 0.2
-#define DESCEND_TIME 3.0 // time to descend from full throttle to zero
-
-extern double controlsTime;
-extern int rollChannel, pitchChannel, throttleChannel, yawChannel;
-
-void failsafe() {
-	armingFailsafe();
-	rcLossFailsafe();
-}
-
-// Prevent arming without zero throttle input
-void armingFailsafe() {
-	static double zeroThrottleTime;
-	static double armingTime;
-	if (!armed) armingTime = t; // stores the last time when the drone was disarmed, therefore contains arming time
-	if (controlsTime > 0 && controls[throttleChannel] < 0.05) zeroThrottleTime = controlsTime;
-	if (armingTime - zeroThrottleTime > 0.1) armed = false; // prevent arming if there was no zero throttle for 0.1 sec
-}
-
-// RC loss failsafe
-void rcLossFailsafe() {
-	if (t - controlsTime > RC_LOSS_TIMEOUT) {
-		descend();
-	}
-}
-
-// Smooth descend on RC lost
-void descend() {
-	mode = STAB;
-	controls[rollChannel] = 0;
-	controls[pitchChannel] = 0;
-	controls[yawChannel] = 0;
-	controls[throttleChannel] -= dt / DESCEND_TIME;
-	if (controls[throttleChannel] < 0) controls[throttleChannel] = 0;
-}

flix/flix.ino

@@ -10,19 +10,20 @@
 #define SERIAL_BAUDRATE 115200
 #define WIFI_ENABLED 1
 
-double t = NAN; // current step time, s
+float t = NAN; // current step time, s
 float dt; // time delta from previous step, s
-int16_t channels[16]; // raw rc channels
-float controls[16]; // normalized controls in range [-1..1] ([0..1] for throttle)
+float controlRoll, controlPitch, controlYaw, controlThrottle; // pilot's inputs, range [-1, 1]
+float controlMode = NAN;
 Vector gyro; // gyroscope data
 Vector acc; // accelerometer data, m/s/s
 Vector rates; // filtered angular rates, rad/s
 Quaternion attitude; // estimated attitude
-float motors[4]; // normalized motors thrust in range [-1..1]
+bool landed; // are we landed and stationary
+float motors[4]; // normalized motors thrust in range [0..1]
 
 void setup() {
 	Serial.begin(SERIAL_BAUDRATE);
-	print("Initializing flix");
+	print("Initializing flix\n");
 	disableBrownOut();
 	setupParameters();
 	setupLED();
@@ -34,7 +35,7 @@ void setup() {
 	setupIMU();
 	setupRC();
 	setLED(false);
-	print("Initializing complete");
+	print("Initializing complete\n");
 }
 
 void loop() {

flix/imu.ino

@@ -4,34 +4,36 @@
 // Work with the IMU sensor
 
 #include <SPI.h>
-#include <MPU9250.h>
+#include <FlixPeriph.h>
+#include "vector.h"
+#include "lpf.h"
 #include "util.h"
 
-MPU9250 IMU(SPI);
+MPU9250 imu(SPI);
 
 Vector accBias;
-Vector gyroBias;
 Vector accScale(1, 1, 1);
+Vector gyroBias;
 
 void setupIMU() {
 	print("Setup IMU\n");
-	IMU.begin();
+	imu.begin();
 	configureIMU();
-	delay(500); // wait a bit before calibrating
-	calibrateGyro();
 }
 
 void configureIMU() {
-	IMU.setAccelRange(IMU.ACCEL_RANGE_4G);
-	IMU.setGyroRange(IMU.GYRO_RANGE_2000DPS);
-	IMU.setDLPF(IMU.DLPF_MAX);
-	IMU.setRate(IMU.RATE_1KHZ_APPROX);
+	imu.setAccelRange(imu.ACCEL_RANGE_4G);
+	imu.setGyroRange(imu.GYRO_RANGE_2000DPS);
+	imu.setDLPF(imu.DLPF_MAX);
+	imu.setRate(imu.RATE_1KHZ_APPROX);
+	imu.setupInterrupt();
 }
 
 void readIMU() {
-	IMU.waitForData();
-	IMU.getGyro(gyro.x, gyro.y, gyro.z);
-	IMU.getAccel(acc.x, acc.y, acc.z);
+	imu.waitForData();
+	imu.getGyro(gyro.x, gyro.y, gyro.z);
+	imu.getAccel(acc.x, acc.y, acc.z);
+	calibrateGyroOnce();
 	// apply scale and bias
 	acc = (acc - accBias) / accScale;
 	gyro = gyro - gyroBias;
@@ -47,47 +49,39 @@ void rotateIMU(Vector& data) {
 	// Axes orientation for various boards: https://github.com/okalachev/flixperiph#imu-axes-orientation
 }
 
-void calibrateGyro() {
-	const int samples = 1000;
-	print("Calibrating gyro, stand still\n");
-	IMU.setGyroRange(IMU.GYRO_RANGE_250DPS); // the most sensitive mode
+void calibrateGyroOnce() {
+	static Delay landedDelay(2);
+	if (!landedDelay.update(landed)) return; // calibrate only if definitely stationary
 
-	gyroBias = Vector(0, 0, 0);
-	for (int i = 0; i < samples; i++) {
-		IMU.waitForData();
-		IMU.getGyro(gyro.x, gyro.y, gyro.z);
-		gyroBias = gyroBias + gyro;
-	}
-	gyroBias = gyroBias / samples;
-
-	printIMUCal();
-	configureIMU();
+	static LowPassFilter<Vector> gyroCalibrationFilter(0.001);
+	gyroBias = gyroCalibrationFilter.update(gyro);
 }
 
 void calibrateAccel() {
 	print("Calibrating accelerometer\n");
-	IMU.setAccelRange(IMU.ACCEL_RANGE_2G); // the most sensitive mode
+	imu.setAccelRange(imu.ACCEL_RANGE_2G); // the most sensitive mode
 
-	print("Place level [8 sec]\n");
+	print("1/6 Place level [8 sec]\n");
 	pause(8);
 	calibrateAccelOnce();
-	print("Place nose up [8 sec]\n");
+	print("2/6 Place nose up [8 sec]\n");
 	pause(8);
 	calibrateAccelOnce();
-	print("Place nose down [8 sec]\n");
+	print("3/6 Place nose down [8 sec]\n");
 	pause(8);
 	calibrateAccelOnce();
-	print("Place on right side [8 sec]\n");
+	print("4/6 Place on right side [8 sec]\n");
 	pause(8);
 	calibrateAccelOnce();
-	print("Place on left side [8 sec]\n");
+	print("5/6 Place on left side [8 sec]\n");
 	pause(8);
 	calibrateAccelOnce();
-	print("Place upside down [8 sec]\n");
+	print("6/6 Place upside down [8 sec]\n");
 	pause(8);
 	calibrateAccelOnce();
 
-	printIMUCal();
+	printIMUCalibration();
+	print("✓ Calibration done!\n");
 	configureIMU();
 }
 
@@ -99,9 +93,9 @@ void calibrateAccelOnce() {
 	// Compute the average of the accelerometer readings
 	acc = Vector(0, 0, 0);
 	for (int i = 0; i < samples; i++) {
-		IMU.waitForData();
+		imu.waitForData();
 		Vector sample;
-		IMU.getAccel(sample.x, sample.y, sample.z);
+		imu.getAccel(sample.x, sample.y, sample.z);
 		acc = acc + sample;
 	}
 	acc = acc / samples;
@@ -113,22 +107,28 @@ void calibrateAccelOnce() {
 	if (acc.x < accMin.x) accMin.x = acc.x;
 	if (acc.y < accMin.y) accMin.y = acc.y;
 	if (acc.z < accMin.z) accMin.z = acc.z;
-	print("acc %f %f %f\n", acc.x, acc.y, acc.z);
-	print("max %f %f %f\n", accMax.x, accMax.y, accMax.z);
-	print("min %f %f %f\n", accMin.x, accMin.y, accMin.z);
 	// Compute scale and bias
 	accScale = (accMax - accMin) / 2 / ONE_G;
 	accBias = (accMax + accMin) / 2;
 }
 
-void printIMUCal() {
+void printIMUCalibration() {
 	print("gyro bias: %f %f %f\n", gyroBias.x, gyroBias.y, gyroBias.z);
 	print("accel bias: %f %f %f\n", accBias.x, accBias.y, accBias.z);
 	print("accel scale: %f %f %f\n", accScale.x, accScale.y, accScale.z);
 }
 
 void printIMUInfo() {
-	IMU.status() ? print("status: ERROR %d\n", IMU.status()) : print("status: OK\n");
-	print("model: %s\n", IMU.getModel());
-	print("who am I: 0x%02X\n", IMU.whoAmI());
+	imu.status() ? print("status: ERROR %d\n", imu.status()) : print("status: OK\n");
+	print("model: %s\n", imu.getModel());
+	print("who am I: 0x%02X\n", imu.whoAmI());
+	print("rate: %.0f\n", loopRate);
+	print("gyro: %f %f %f\n", rates.x, rates.y, rates.z);
+	print("acc: %f %f %f\n", acc.x, acc.y, acc.z);
+	imu.waitForData();
+	Vector rawGyro, rawAcc;
+	imu.getGyro(rawGyro.x, rawGyro.y, rawGyro.z);
+	imu.getAccel(rawAcc.x, rawAcc.y, rawAcc.z);
+	print("raw gyro: %f %f %f\n", rawGyro.x, rawGyro.y, rawGyro.z);
+	print("raw acc: %f %f %f\n", rawAcc.x, rawAcc.y, rawAcc.z);
 }

flix/log.ino

@@ -10,7 +10,6 @@
 #define LOG_PERIOD 1.0 / LOG_RATE
 #define LOG_SIZE LOG_DURATION * LOG_RATE
 
-float tFloat;
 Vector attitudeEuler;
 Vector attitudeTargetEuler;
 
@@ -20,7 +19,7 @@ struct LogEntry {
 };
 
 LogEntry logEntries[] = {
-	{"t", &tFloat},
+	{"t", &t},
 	{"rates.x", &rates.x},
 	{"rates.y", &rates.y},
 	{"rates.z", &rates.z},
@@ -40,15 +39,14 @@ const int logColumns = sizeof(logEntries) / sizeof(logEntries[0]);
 float logBuffer[LOG_SIZE][logColumns];
 
 void prepareLogData() {
-	tFloat = t;
-	attitudeEuler = attitude.toEulerZYX();
-	attitudeTargetEuler = attitudeTarget.toEulerZYX();
+	attitudeEuler = attitude.toEuler();
+	attitudeTargetEuler = attitudeTarget.toEuler();
 }
 
 void logData() {
 	if (!armed) return;
 	static int logPointer = 0;
-	static double logTime = 0;
+	static float logTime = 0;
 	if (t - logTime < LOG_PERIOD) return;
 	logTime = t;
 

flix/lpf.h

@@ -22,7 +22,8 @@ public:
 			output = input;
 			initialized = true;
 		}
-		return output = output * (1 - alpha) + input * alpha;
+
+		return output += alpha * (input - output);
 	}
 
 	void setCutOffFrequency(float cutOffFreq, float dt) {

flix/mavlink.ino

@@ -10,13 +10,13 @@
 #define SYSTEM_ID 1
 #define PERIOD_SLOW 1.0
 #define PERIOD_FAST 0.1
-#define MAVLINK_CONTROL_SCALE 0.7f
 #define MAVLINK_CONTROL_YAW_DEAD_ZONE 0.1f
 
-float mavlinkControlScale = 0.7;
+bool mavlinkConnected = false;
+String mavlinkPrintBuffer;
 
-extern double controlsTime;
-extern int rollChannel, pitchChannel, throttleChannel, yawChannel, armedChannel, modeChannel;
+extern float controlTime;
+extern float controlRoll, controlPitch, controlThrottle, controlYaw, controlMode;
 
 void processMavlink() {
 	sendMavlink();
@@ -24,8 +24,10 @@ void processMavlink() {
 }
 
 void sendMavlink() {
-	static double lastSlow = 0;
-	static double lastFast = 0;
+	sendMavlinkPrint();
+
+	static float lastSlow = 0;
+	static float lastFast = 0;
 
 	mavlink_message_t msg;
 	uint32_t time = t * 1000;
@@ -33,35 +35,40 @@ void sendMavlink() {
 	if (t - lastSlow >= PERIOD_SLOW) {
 		lastSlow = t;
 
-		mavlink_msg_heartbeat_pack(SYSTEM_ID, MAV_COMP_ID_AUTOPILOT1, &msg, MAV_TYPE_QUADROTOR,
-			MAV_AUTOPILOT_GENERIC, MAV_MODE_FLAG_MANUAL_INPUT_ENABLED | (armed ? MAV_MODE_FLAG_SAFETY_ARMED : 0),
-			0, MAV_STATE_STANDBY);
+		mavlink_msg_heartbeat_pack(SYSTEM_ID, MAV_COMP_ID_AUTOPILOT1, &msg, MAV_TYPE_QUADROTOR, MAV_AUTOPILOT_GENERIC,
+			(armed ? MAV_MODE_FLAG_SAFETY_ARMED : 0) |
+			((mode == STAB) ? MAV_MODE_FLAG_STABILIZE_ENABLED : 0) |
+			((mode == AUTO) ? MAV_MODE_FLAG_AUTO_ENABLED : MAV_MODE_FLAG_MANUAL_INPUT_ENABLED),
+			mode, MAV_STATE_STANDBY);
+		sendMessage(&msg);
+
+		if (!mavlinkConnected) return; // send only heartbeat until connected
+
+		mavlink_msg_extended_sys_state_pack(SYSTEM_ID, MAV_COMP_ID_AUTOPILOT1, &msg,
+			MAV_VTOL_STATE_UNDEFINED, landed ? MAV_LANDED_STATE_ON_GROUND : MAV_LANDED_STATE_IN_AIR);
 		sendMessage(&msg);
 	}
 
-	if (t - lastFast >= PERIOD_FAST) {
+	if (t - lastFast >= PERIOD_FAST && mavlinkConnected) {
 		lastFast = t;
 
 		const float zeroQuat[] = {0, 0, 0, 0};
-		Quaternion attitudeFRD = fluToFrd(attitude); // MAVLink uses FRD coordinate system
 		mavlink_msg_attitude_quaternion_pack(SYSTEM_ID, MAV_COMP_ID_AUTOPILOT1, &msg,
-			time, attitudeFRD.w, attitudeFRD.x, attitudeFRD.y, attitudeFRD.z, rates.x, rates.y, rates.z, zeroQuat);
+			time, attitude.w, attitude.x, -attitude.y, -attitude.z, rates.x, -rates.y, -rates.z, zeroQuat); // convert to frd
 		sendMessage(&msg);
 
-		mavlink_msg_rc_channels_scaled_pack(SYSTEM_ID, MAV_COMP_ID_AUTOPILOT1, &msg, controlsTime * 1000, 0,
-			controls[0] * 10000, controls[1] * 10000, controls[2] * 10000,
-			controls[3] * 10000, controls[4] * 10000, controls[5] * 10000,
-			INT16_MAX, INT16_MAX, UINT8_MAX);
-		sendMessage(&msg);
+		mavlink_msg_rc_channels_raw_pack(SYSTEM_ID, MAV_COMP_ID_AUTOPILOT1, &msg, controlTime * 1000, 0,
+			channels[0], channels[1], channels[2], channels[3], channels[4], channels[5], channels[6], channels[7], UINT8_MAX);
+		if (channels[0] != 0) sendMessage(&msg); // 0 means no RC input
 
-		float actuator[32];
-		memcpy(actuator, motors, sizeof(motors));
-		mavlink_msg_actuator_output_status_pack(SYSTEM_ID, MAV_COMP_ID_AUTOPILOT1, &msg, time, 4, actuator);
+		float controls[8];
+		memcpy(controls, motors, sizeof(motors));
+		mavlink_msg_actuator_control_target_pack(SYSTEM_ID, MAV_COMP_ID_AUTOPILOT1, &msg, time, 0, controls);
 		sendMessage(&msg);
 
 		mavlink_msg_scaled_imu_pack(SYSTEM_ID, MAV_COMP_ID_AUTOPILOT1, &msg, time,
-			acc.x * 1000, acc.y * 1000, acc.z * 1000,
-			gyro.x * 1000, gyro.y * 1000, gyro.z * 1000,
+			acc.x * 1000, -acc.y * 1000, -acc.z * 1000, // convert to frd
+			gyro.x * 1000, -gyro.y * 1000, -gyro.z * 1000,
 			0, 0, 0, 0);
 		sendMessage(&msg);
 	}
@@ -76,6 +83,7 @@ void sendMessage(const void *msg) {
 void receiveMavlink() {
 	uint8_t buf[MAVLINK_MAX_PACKET_LEN];
 	int len = receiveWiFi(buf, MAVLINK_MAX_PACKET_LEN);
+	if (len) mavlinkConnected = true;
 
 	// New packet, parse it
 	mavlink_message_t msg;
@@ -88,22 +96,21 @@ void receiveMavlink() {
 }
 
 void handleMavlink(const void *_msg) {
-	const mavlink_message_t &msg = *(mavlink_message_t *)_msg;
+	const mavlink_message_t& msg = *(mavlink_message_t *)_msg;
 
 	if (msg.msgid == MAVLINK_MSG_ID_MANUAL_CONTROL) {
 		mavlink_manual_control_t m;
 		mavlink_msg_manual_control_decode(&msg, &m);
 		if (m.target && m.target != SYSTEM_ID) return; // 0 is broadcast
 
-		controls[throttleChannel] = m.z / 1000.0f;
-		controls[pitchChannel] = m.x / 1000.0f * mavlinkControlScale;
-		controls[rollChannel] = m.y / 1000.0f * mavlinkControlScale;
-		controls[yawChannel] = m.r / 1000.0f * mavlinkControlScale;
-		controls[modeChannel] = 1; // STAB mode
-		controls[armedChannel] = 1; // armed
-		controlsTime = t;
+		controlThrottle = m.z / 1000.0f;
+		controlPitch = m.x / 1000.0f;
+		controlRoll = m.y / 1000.0f;
+		controlYaw = m.r / 1000.0f;
+		controlMode = NAN;
+		controlTime = t;
 
-		if (abs(controls[yawChannel]) < MAVLINK_CONTROL_YAW_DEAD_ZONE) controls[yawChannel] = 0;
+		if (abs(controlYaw) < MAVLINK_CONTROL_YAW_DEAD_ZONE) controlYaw = 0;
 	}
 
 	if (msg.msgid == MAVLINK_MSG_ID_PARAM_REQUEST_LIST) {
@@ -171,43 +178,95 @@ void handleMavlink(const void *_msg) {
 		doCommand(data, true);
 	}
 
+	if (msg.msgid == MAVLINK_MSG_ID_SET_ATTITUDE_TARGET) {
+		if (mode != AUTO) return;
+
+		mavlink_set_attitude_target_t m;
+		mavlink_msg_set_attitude_target_decode(&msg, &m);
+		if (m.target_system && m.target_system != SYSTEM_ID) return;
+
+		// copy attitude, rates and thrust targets
+		ratesTarget.x = m.body_roll_rate;
+		ratesTarget.y = -m.body_pitch_rate; // convert to flu
+		ratesTarget.z = -m.body_yaw_rate;
+		attitudeTarget.w = m.q[0];
+		attitudeTarget.x = m.q[1];
+		attitudeTarget.y = -m.q[2];
+		attitudeTarget.z = -m.q[3];
+		thrustTarget = m.thrust;
+		ratesExtra = Vector(0, 0, 0);
+
+		if (m.type_mask & ATTITUDE_TARGET_TYPEMASK_ATTITUDE_IGNORE) attitudeTarget.invalidate();
+		armed = m.thrust > 0;
+	}
+
+	if (msg.msgid == MAVLINK_MSG_ID_SET_ACTUATOR_CONTROL_TARGET) {
+		if (mode != AUTO) return;
+
+		mavlink_set_actuator_control_target_t m;
+		mavlink_msg_set_actuator_control_target_decode(&msg, &m);
+		if (m.target_system && m.target_system != SYSTEM_ID) return;
+
+		attitudeTarget.invalidate();
+		ratesTarget.invalidate();
+		torqueTarget.invalidate();
+		memcpy(motors, m.controls, sizeof(motors)); // copy motor thrusts
+		armed = motors[0] > 0 || motors[1] > 0 || motors[2] > 0 || motors[3] > 0;
+	}
+
 	// Handle commands
 	if (msg.msgid == MAVLINK_MSG_ID_COMMAND_LONG) {
 		mavlink_command_long_t m;
 		mavlink_msg_command_long_decode(&msg, &m);
 		if (m.target_system && m.target_system != SYSTEM_ID) return;
-		mavlink_message_t ack;
 		mavlink_message_t response;
+		bool accepted = false;
 
 		if (m.command == MAV_CMD_REQUEST_MESSAGE && m.param1 == MAVLINK_MSG_ID_AUTOPILOT_VERSION) {
-			mavlink_msg_command_ack_pack(SYSTEM_ID, MAV_COMP_ID_AUTOPILOT1, &ack, m.command, MAV_RESULT_ACCEPTED, UINT8_MAX, 0, msg.sysid, msg.compid);
-			sendMessage(&ack);
+			accepted = true;
 			mavlink_msg_autopilot_version_pack(SYSTEM_ID, MAV_COMP_ID_AUTOPILOT1, &response,
 				MAV_PROTOCOL_CAPABILITY_PARAM_FLOAT | MAV_PROTOCOL_CAPABILITY_MAVLINK2, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0);
 			sendMessage(&response);
-		} else {
-			mavlink_msg_command_ack_pack(SYSTEM_ID, MAV_COMP_ID_AUTOPILOT1, &ack, m.command, MAV_RESULT_UNSUPPORTED, UINT8_MAX, 0, msg.sysid, msg.compid);
-			sendMessage(&ack);
 		}
+
+		if (m.command == MAV_CMD_COMPONENT_ARM_DISARM) {
+			if (m.param1 && controlThrottle > 0.05) return; // don't arm if throttle is not low
+			accepted = true;
+			armed = m.param1 == 1;
+		}
+
+		if (m.command == MAV_CMD_DO_SET_MODE) {
+			if (m.param2 < 0 || m.param2 > AUTO) return; // incorrect mode
+			accepted = true;
+			mode = m.param2;
+		}
+
+		// send command ack
+		mavlink_message_t ack;
+		mavlink_msg_command_ack_pack(SYSTEM_ID, MAV_COMP_ID_AUTOPILOT1, &ack, m.command, accepted ? MAV_RESULT_ACCEPTED : MAV_RESULT_UNSUPPORTED, UINT8_MAX, 0, msg.sysid, msg.compid);
+		sendMessage(&ack);
 	}
 }
 
 // Send shell output to GCS
 void mavlinkPrint(const char* str) {
-	// Send data in chunks
+	mavlinkPrintBuffer += str;
+}
+
+void sendMavlinkPrint() {
+	// Send mavlink print data in chunks
+	const char *str = mavlinkPrintBuffer.c_str();
 	for (int i = 0; i < strlen(str); i += MAVLINK_MSG_SERIAL_CONTROL_FIELD_DATA_LEN) {
 		char data[MAVLINK_MSG_SERIAL_CONTROL_FIELD_DATA_LEN + 1];
 		strlcpy(data, str + i, sizeof(data));
 		mavlink_message_t msg;
 		mavlink_msg_serial_control_pack(SYSTEM_ID, MAV_COMP_ID_AUTOPILOT1, &msg,
-			SERIAL_CONTROL_DEV_SHELL, 0, 0, 0, strlen(data), (uint8_t *)data, 0, 0);
+			SERIAL_CONTROL_DEV_SHELL,
+			i + MAVLINK_MSG_SERIAL_CONTROL_FIELD_DATA_LEN < strlen(str) ? SERIAL_CONTROL_FLAG_MULTI : 0, // more chunks to go
+			0, 0, strlen(data), (uint8_t *)data, 0, 0);
 		sendMessage(&msg);
 	}
-}
-
-// Convert Forward-Left-Up to Forward-Right-Down quaternion
-inline Quaternion fluToFrd(const Quaternion &q) {
-	return Quaternion(q.w, q.x, -q.y, -q.z);
+	mavlinkPrintBuffer.clear();
 }
 
 #endif

flix/motors.ino

@@ -11,8 +11,8 @@
 #define MOTOR_2_PIN 14 // front right
 #define MOTOR_3_PIN 15 // front left
 
-#define PWM_FREQUENCY 1000
-#define PWM_RESOLUTION 12
+#define PWM_FREQUENCY 78000
+#define PWM_RESOLUTION 10
 #define PWM_STOP 0
 #define PWM_MIN 0
 #define PWM_MAX 1000000 / PWM_FREQUENCY
@@ -25,37 +25,39 @@ const int MOTOR_FRONT_LEFT = 3;
 
 void setupMotors() {
 	print("Setup Motors\n");
-
-	// configure pins
+#ifdef ESP32
 	ledcAttach(MOTOR_0_PIN, PWM_FREQUENCY, PWM_RESOLUTION);
 	ledcAttach(MOTOR_1_PIN, PWM_FREQUENCY, PWM_RESOLUTION);
 	ledcAttach(MOTOR_2_PIN, PWM_FREQUENCY, PWM_RESOLUTION);
 	ledcAttach(MOTOR_3_PIN, PWM_FREQUENCY, PWM_RESOLUTION);
-
+#else
+	analogWriteResolution(PWM_RESOLUTION);
+	analogWriteFrequency(PWM_FREQUENCY);
+#endif
 	sendMotors();
 	print("Motors initialized\n");
 }
 
 int getDutyCycle(float value) {
 	value = constrain(value, 0, 1);
-	float pwm = mapff(value, 0, 1, PWM_MIN, PWM_MAX);
+	float pwm = mapf(value, 0, 1, PWM_MIN, PWM_MAX);
 	if (value == 0) pwm = PWM_STOP;
-	float duty = mapff(pwm, 0, 1000000 / PWM_FREQUENCY, 0, (1 << PWM_RESOLUTION) - 1);
+	float duty = mapf(pwm, 0, 1000000 / PWM_FREQUENCY, 0, (1 << PWM_RESOLUTION) - 1);
 	return round(duty);
 }
 
 void sendMotors() {
-	ledcWrite(MOTOR_0_PIN, getDutyCycle(motors[0]));
-	ledcWrite(MOTOR_1_PIN, getDutyCycle(motors[1]));
-	ledcWrite(MOTOR_2_PIN, getDutyCycle(motors[2]));
-	ledcWrite(MOTOR_3_PIN, getDutyCycle(motors[3]));
+	analogWrite(MOTOR_0_PIN, getDutyCycle(motors[0]));
+	analogWrite(MOTOR_1_PIN, getDutyCycle(motors[1]));
+	analogWrite(MOTOR_2_PIN, getDutyCycle(motors[2]));
+	analogWrite(MOTOR_3_PIN, getDutyCycle(motors[3]));
 }
 
 bool motorsActive() {
 	return motors[0] != 0 || motors[1] != 0 || motors[2] != 0 || motors[3] != 0;
 }
 
-void testMotor(uint8_t n) {
+void testMotor(int n) {
 	print("Testing motor %d\n", n);
 	motors[n] = 1;
 	delay(50); // ESP32 may need to wait until the end of the current cycle to change duty https://github.com/espressif/arduino-esp32/issues/5306

flix/parameters.ino

@@ -5,14 +5,14 @@
 
 #include <Preferences.h>
 
-extern float channelNeutral[16];
+extern float channelZero[16];
 extern float channelMax[16];
-extern float mavlinkControlScale;
+extern float rollChannel, pitchChannel, throttleChannel, yawChannel, armedChannel, modeChannel;
 
 Preferences storage;
 
 struct Parameter {
-	const char *name;
+	const char *name; // max length is 16
 	float *variable;
 	float value; // cache
 };
@@ -48,18 +48,15 @@ Parameter parameters[] = {
 	{"ACC_SCALE_X", &accScale.x},
 	{"ACC_SCALE_Y", &accScale.y},
 	{"ACC_SCALE_Z", &accScale.z},
-	{"GYRO_BIAS_X", &gyroBias.x},
-	{"GYRO_BIAS_Y", &gyroBias.y},
-	{"GYRO_BIAS_Z", &gyroBias.z},
 	// rc
-	{"RC_NEUTRAL_0", &channelNeutral[0]},
-	{"RC_NEUTRAL_1", &channelNeutral[1]},
-	{"RC_NEUTRAL_2", &channelNeutral[2]},
-	{"RC_NEUTRAL_3", &channelNeutral[3]},
-	{"RC_NEUTRAL_4", &channelNeutral[4]},
-	{"RC_NEUTRAL_5", &channelNeutral[5]},
-	{"RC_NEUTRAL_6", &channelNeutral[6]},
-	{"RC_NEUTRAL_7", &channelNeutral[7]},
+	{"RC_ZERO_0", &channelZero[0]},
+	{"RC_ZERO_1", &channelZero[1]},
+	{"RC_ZERO_2", &channelZero[2]},
+	{"RC_ZERO_3", &channelZero[3]},
+	{"RC_ZERO_4", &channelZero[4]},
+	{"RC_ZERO_5", &channelZero[5]},
+	{"RC_ZERO_6", &channelZero[6]},
+	{"RC_ZERO_7", &channelZero[7]},
 	{"RC_MAX_0", &channelMax[0]},
 	{"RC_MAX_1", &channelMax[1]},
 	{"RC_MAX_2", &channelMax[2]},
@@ -68,10 +65,11 @@ Parameter parameters[] = {
 	{"RC_MAX_5", &channelMax[5]},
 	{"RC_MAX_6", &channelMax[6]},
 	{"RC_MAX_7", &channelMax[7]},
-#if WIFI_ENABLED
-	// MAVLink
-	{"MAV_CTRL_SCALE", &mavlinkControlScale},
-#endif
+	{"RC_ROLL", &rollChannel},
+	{"RC_PITCH", &pitchChannel},
+	{"RC_THROTTLE", &throttleChannel},
+	{"RC_YAW", &yawChannel},
+	{"RC_MODE", &modeChannel},
 };
 
 void setupParameters() {
@@ -120,7 +118,7 @@ bool setParameter(const char *name, const float value) {
 }
 
 void syncParameters() {
-	static double lastSync = 0;
+	static float lastSync = 0;
 	if (t - lastSync < 1) return; // sync once per second
 	if (motorsActive()) return; // don't use flash while flying, it may cause a delay
 	lastSync = t;

flix/pid.h

@@ -9,40 +9,44 @@
 
 class PID {
 public:
-	float p = 0;
-	float i = 0;
-	float d = 0;
-	float windup = 0;
+	float p, i, d;
+	float windup;
+	float dtMax;
 
 	float derivative = 0;
 	float integral = 0;
 
 	LowPassFilter<float> lpf; // low pass filter for derivative term
 
-	PID(float p, float i, float d, float windup = 0, float dAlpha = 1) : p(p), i(i), d(d), windup(windup), lpf(dAlpha) {};
+	PID(float p, float i, float d, float windup = 0, float dAlpha = 1, float dtMax = 0.1) :
+		p(p), i(i), d(d), windup(windup), lpf(dAlpha), dtMax(dtMax) {}
 
-	float update(float error, float dt) {
-		integral += error * dt;
+	float update(float error) {
+		float dt = t - prevTime;
 
-		if (isfinite(prevError) && dt > 0) {
-			// calculate derivative if both dt and prevError are valid
-			derivative = (error - prevError) / dt;
-
-			// apply low pass filter to derivative
-			derivative = lpf.update(derivative);
+		if (dt > 0 && dt < dtMax) {
+			integral += error * dt;
+			derivative = lpf.update((error - prevError) / dt); // compute derivative and apply low-pass filter
+		} else {
+			integral = 0;
+			derivative = 0;
 		}
 
 		prevError = error;
+		prevTime = t;
 
 		return p * error + constrain(i * integral, -windup, windup) + d * derivative; // PID
 	}
 
 	void reset() {
 		prevError = NAN;
+		prevTime = NAN;
 		integral = 0;
 		derivative = 0;
+		lpf.reset();
 	}
 
 private:
 	float prevError = NAN;
+	float prevTime = NAN;
 };

flix/quaternion.h

@@ -15,22 +15,22 @@ public:
 
 	Quaternion(float w, float x, float y, float z): w(w), x(x), y(y), z(z) {};
 
-	static Quaternion fromAxisAngle(float a, float b, float c, float angle) {
+	static Quaternion fromAxisAngle(const Vector& axis, float angle) {
 		float halfAngle = angle * 0.5;
 		float sin2 = sin(halfAngle);
 		float cos2 = cos(halfAngle);
-		float sinNorm = sin2 / sqrt(a * a + b * b + c * c);
-		return Quaternion(cos2, a * sinNorm, b * sinNorm, c * sinNorm);
+		float sinNorm = sin2 / axis.norm();
+		return Quaternion(cos2, axis.x * sinNorm, axis.y * sinNorm, axis.z * sinNorm);
 	}
 
-	static Quaternion fromAngularRates(const Vector& rates) {
-		if (rates.zero()) {
+	static Quaternion fromRotationVector(const Vector& rotation) {
+		if (rotation.zero()) {
 			return Quaternion();
 		}
-		return Quaternion::fromAxisAngle(rates.x, rates.y, rates.z, rates.norm());
+		return Quaternion::fromAxisAngle(rotation, rotation.norm());
 	}
 
-	static Quaternion fromEulerZYX(const Vector& euler) {
+	static Quaternion fromEuler(const Vector& euler) {
 		float cx = cos(euler.x / 2);
 		float cy = cos(euler.y / 2);
 		float cz = cos(euler.z / 2);
@@ -45,7 +45,7 @@ public:
 			cx * cy * sz - sx * sy * cz);
 	}
 
-	static Quaternion fromBetweenVectors(Vector u, Vector v) {
+	static Quaternion fromBetweenVectors(const Vector& u, const Vector& v) {
 		float dot = u.x * v.x + u.y * v.y + u.z * v.z;
 		float w1 = u.y * v.z - u.z * v.y;
 		float w2 = u.z * v.x - u.x * v.z;
@@ -60,14 +60,54 @@ public:
 		return ret;
 	}
 
-	void toAxisAngle(float& a, float& b, float& c, float& angle) const {
-		angle = acos(w) * 2;
-		a = x / sin(angle / 2);
-		b = y / sin(angle / 2);
-		c = z / sin(angle / 2);
+	bool finite() const {
+		return isfinite(w) && isfinite(x) && isfinite(y) && isfinite(z);
 	}
 
-	Vector toEulerZYX() const {
+	bool valid() const {
+		return finite();
+	}
+
+	bool invalid() const {
+		return !valid();
+	}
+
+	void invalidate() {
+		w = NAN;
+		x = NAN;
+		y = NAN;
+		z = NAN;
+	}
+
+
+	float norm() const {
+		return sqrt(w * w + x * x + y * y + z * z);
+	}
+
+	void normalize() {
+		float n = norm();
+		w /= n;
+		x /= n;
+		y /= n;
+		z /= n;
+	}
+
+	void toAxisAngle(Vector& axis, float& angle) const {
+		angle = acos(w) * 2;
+		axis.x = x / sin(angle / 2);
+		axis.y = y / sin(angle / 2);
+		axis.z = z / sin(angle / 2);
+	}
+
+	Vector toRotationVector() const {
+		if (w == 1 && x == 0 && y == 0 && z == 0) return Vector(0, 0, 0); // neutral quaternion
+		float angle;
+		Vector axis;
+		toAxisAngle(axis, angle);
+		return angle * axis;
+	}
+
+	Vector toEuler() const {
 		// https://github.com/ros/geometry2/blob/589caf083cae9d8fae7effdb910454b4681b9ec1/tf2/include/tf2/impl/utils.h#L87
 		Vector euler;
 		float sqx = x * x;
@@ -92,38 +132,31 @@ public:
 		return euler;
 	}
 
+	float getRoll() const {
+		return toEuler().x;
+	}
+
+	float getPitch() const {
+		return toEuler().y;
+	}
+
 	float getYaw() const {
-		// https://github.com/ros/geometry2/blob/589caf083cae9d8fae7effdb910454b4681b9ec1/tf2/include/tf2/impl/utils.h#L122
-		float yaw;
-		float sqx = x * x;
-		float sqy = y * y;
-		float sqz = z * z;
-		float sqw = w * w;
-		double sarg = -2 * (x * z - w * y) / (sqx + sqy + sqz + sqw);
-		if (sarg <= -0.99999) {
-			yaw = -2 * atan2(y, x);
-		} else if (sarg >= 0.99999) {
-			yaw = 2 * atan2(y, x);
-		} else {
-			yaw = atan2(2 * (x * y + w * z), sqw + sqx - sqy - sqz);
-		}
-		return yaw;
+		return toEuler().z;
+	}
+
+	void setRoll(float roll) {
+		Vector euler = toEuler();
+		*this = Quaternion::fromEuler(Vector(roll, euler.y, euler.z));
+	}
+
+	void setPitch(float pitch) {
+		Vector euler = toEuler();
+		*this = Quaternion::fromEuler(Vector(euler.x, pitch, euler.z));
 	}
 
 	void setYaw(float yaw) {
-		// TODO: optimize?
-		Vector euler = toEulerZYX();
-		euler.z = yaw;
-		(*this) = Quaternion::fromEulerZYX(euler);
-	}
-
-	Quaternion& operator *= (const Quaternion& q) {
-		Quaternion ret(
-			w * q.w - x * q.x - y * q.y - z * q.z,
-			w * q.x + x * q.w + y * q.z - z * q.y,
-			w * q.y + y * q.w + z * q.x - x * q.z,
-			w * q.z + z * q.w + x * q.y - y * q.x);
-		return (*this = ret);
+		Vector euler = toEuler();
+		*this = Quaternion::fromEuler(Vector(euler.x, euler.y, yaw));
 	}
 
 	Quaternion operator * (const Quaternion& q) const {
@@ -134,6 +167,14 @@ public:
 			w * q.z + z * q.w + x * q.y - y * q.x);
 	}
 
+	bool operator == (const Quaternion& q) const {
+		return w == q.w && x == q.x && y == q.y && z == q.z;
+	}
+
+	bool operator != (const Quaternion& q) const {
+		return !(*this == q);
+	}
+
 	Quaternion inversed() const {
 		float normSqInv = 1 / (w * w + x * x + y * y + z * z);
 		return Quaternion(
@@ -143,18 +184,6 @@ public:
 			-z * normSqInv);
 	}
 
-	float norm() const {
-		return sqrt(w * w + x * x + y * y + z * z);
-	}
-
-	void normalize() {
-		float n = norm();
-		w /= n;
-		x /= n;
-		y /= n;
-		z /= n;
-	}
-
 	Vector conjugate(const Vector& v) const {
 		Quaternion qv(0, v.x, v.y, v.z);
 		Quaternion res = (*this) * qv * inversed();
@@ -167,22 +196,27 @@ public:
 		return Vector(res.x, res.y, res.z);
 	}
 
-	// Rotate vector by quaternion
-	Vector rotateVector(const Vector& v) const {
-		return conjugateInversed(v);
-	}
-
 	// Rotate quaternion by quaternion
-	Quaternion rotate(const Quaternion& q, const bool normalize = true) const {
-		Quaternion rotated = (*this) * q;
+	static Quaternion rotate(const Quaternion& a, const Quaternion& b, const bool normalize = true) {
+		Quaternion rotated = a * b;
 		if (normalize) {
 			rotated.normalize();
 		}
 		return rotated;
 	}
 
-	bool finite() const {
-		return isfinite(w) && isfinite(x) && isfinite(y) && isfinite(z);
+	// Rotate vector by quaternion
+	static Vector rotateVector(const Vector& v, const Quaternion& q) {
+		return q.conjugateInversed(v);
+	}
+
+	// Quaternion between two quaternions a and b
+	static Quaternion between(const Quaternion& a, const Quaternion& b, const bool normalize = true) {
+		Quaternion q = a * b.inversed();
+		if (normalize) {
+			q.normalize();
+		}
+		return q;
 	}
 
 	size_t printTo(Print& p) const {

flix/rc.ino

@@ -6,64 +6,91 @@
 #include <SBUS.h>
 #include "util.h"
 
-SBUS RC(Serial2); // NOTE: Use RC(Serial2, 16, 17) if you use the old UART2 pins
+SBUS rc(Serial2); // NOTE: Use RC(Serial2, 16, 17) if you use the old UART2 pins
 
-// RC channels mapping:
-int rollChannel = 0;
-int pitchChannel = 1;
-int throttleChannel = 2;
-int yawChannel = 3;
-int armedChannel = 4;
-int modeChannel = 5;
+uint16_t channels[16]; // raw rc channels
+float controlTime; // time of the last controls update
+float channelZero[16]; // calibration zero values
+float channelMax[16]; // calibration max values
 
-double controlsTime; // time of the last controls update
-float channelNeutral[16] = {NAN}; // first element NAN means not calibrated
-float channelMax[16];
+// Channels mapping (using float to store in parameters):
+float rollChannel = NAN, pitchChannel = NAN, throttleChannel = NAN, yawChannel = NAN, modeChannel = NAN;
 
 void setupRC() {
 	print("Setup RC\n");
-	RC.begin();
+	rc.begin();
 }
 
 bool readRC() {
-	if (RC.read()) {
-		SBUSData data = RC.data();
-		memcpy(channels, data.ch, sizeof(channels)); // copy channels data
+	if (rc.read()) {
+		SBUSData data = rc.data();
+		for (int i = 0; i < 16; i++) channels[i] = data.ch[i]; // copy channels data
 		normalizeRC();
-		controlsTime = t;
+		controlTime = t;
 		return true;
 	}
 	return false;
 }
 
 void normalizeRC() {
-	if (isnan(channelNeutral[0])) return; // skip if not calibrated
-	for (uint8_t i = 0; i < 16; i++) {
-		controls[i] = mapf(channels[i], channelNeutral[i], channelMax[i], 0, 1);
+	float controls[16];
+	for (int i = 0; i < 16; i++) {
+		controls[i] = mapf(channels[i], channelZero[i], channelMax[i], 0, 1);
 	}
+	// Update control values
+	controlRoll = rollChannel >= 0 ? controls[(int)rollChannel] : NAN;
+	controlPitch = pitchChannel >= 0 ? controls[(int)pitchChannel] : NAN;
+	controlYaw = yawChannel >= 0 ? controls[(int)yawChannel] : NAN;
+	controlThrottle = throttleChannel >= 0 ? controls[(int)throttleChannel] : NAN;
+	controlMode = modeChannel >= 0 ? controls[(int)modeChannel] : NAN;
 }
 
 void calibrateRC() {
-	print("Calibrate RC: move all sticks to maximum positions [4 sec]\n");
-	print("··o     ··o\n···     ···\n···     ···\n");
-	pause(4);
-	while (!readRC());
-	for (int i = 0; i < 16; i++) {
-		channelMax[i] = channels[i];
-	}
-	print("Calibrate RC: move all sticks to neutral positions [4 sec]\n");
-	print("···     ···\n···     ·o·\n·o·     ···\n");
-	pause(4);
-	while (!readRC());
-	for (int i = 0; i < 16; i++) {
-		channelNeutral[i] = channels[i];
-	}
-	printRCCal();
+	uint16_t zero[16];
+	uint16_t center[16];
+	uint16_t max[16];
+	print("1/8 Calibrating RC: put all switches to default positions [3 sec]\n");
+	pause(3);
+	calibrateRCChannel(NULL, zero, zero, "2/8 Move sticks [3 sec]\n...     ...\n...     .o.\n.o.     ...\n");
+	calibrateRCChannel(NULL, center, center, "3/8 Move sticks [3 sec]\n...     ...\n.o.     .o.\n...     ...\n");
+	calibrateRCChannel(&throttleChannel, zero, max, "4/8 Move sticks [3 sec]\n.o.     ...\n...     .o.\n...     ...\n");
+	calibrateRCChannel(&yawChannel, center, max, "5/8 Move sticks [3 sec]\n...     ...\n..o     .o.\n...     ...\n");
+	calibrateRCChannel(&pitchChannel, zero, max, "6/8 Move sticks [3 sec]\n...     .o.\n...     ...\n.o.     ...\n");
+	calibrateRCChannel(&rollChannel, zero, max, "7/8 Move sticks [3 sec]\n...     ...\n...     ..o\n.o.     ...\n");
+	calibrateRCChannel(&modeChannel, zero, max, "8/8 Put mode switch to max [3 sec]\n");
+	printRCCalibration();
 }
 
-void printRCCal() {
-	for (int i = 0; i < sizeof(channelNeutral) / sizeof(channelNeutral[0]); i++) print("%g ", channelNeutral[i]);
-	print("\n");
-	for (int i = 0; i < sizeof(channelMax) / sizeof(channelMax[0]); i++) print("%g ", channelMax[i]);
-	print("\n");
+void calibrateRCChannel(float *channel, uint16_t in[16], uint16_t out[16], const char *str) {
+	print("%s", str);
+	pause(3);
+	for (int i = 0; i < 30; i++) readRC(); // try update 30 times max
+	memcpy(out, channels, sizeof(channels));
+
+	if (channel == NULL) return; // no channel to calibrate
+
+	// Find channel that changed the most between in and out
+	int ch = -1, diff = 0;
+	for (int i = 0; i < 16; i++) {
+		if (abs(out[i] - in[i]) > diff) {
+			ch = i;
+			diff = abs(out[i] - in[i]);
+		}
+	}
+	if (ch >= 0 && diff > 10) { // difference threshold is 10
+		*channel = ch;
+		channelZero[ch] = in[ch];
+		channelMax[ch] = out[ch];
+	} else {
+		*channel = NAN;
+	}
+}
+
+void printRCCalibration() {
+	print("Control   Ch     Zero   Max\n");
+	print("Roll      %-7g%-7g%-7g\n", rollChannel, rollChannel >= 0 ? channelZero[(int)rollChannel] : NAN, rollChannel >= 0 ? channelMax[(int)rollChannel] : NAN);
+	print("Pitch     %-7g%-7g%-7g\n", pitchChannel, pitchChannel >= 0 ? channelZero[(int)pitchChannel] : NAN, pitchChannel >= 0 ? channelMax[(int)pitchChannel] : NAN);
+	print("Yaw       %-7g%-7g%-7g\n", yawChannel, yawChannel >= 0 ? channelZero[(int)yawChannel] : NAN, yawChannel >= 0 ? channelMax[(int)yawChannel] : NAN);
+	print("Throttle  %-7g%-7g%-7g\n", throttleChannel, throttleChannel >= 0 ? channelZero[(int)throttleChannel] : NAN, throttleChannel >= 0 ? channelMax[(int)throttleChannel] : NAN);
+	print("Mode      %-7g%-7g%-7g\n", modeChannel, modeChannel >= 0 ? channelZero[(int)modeChannel] : NAN, modeChannel >= 0 ? channelMax[(int)modeChannel] : NAN);
 }

flix/safety.ino

@@ -0,0 +1,48 @@
+// Copyright (c) 2024 Oleg Kalachev <okalachev@gmail.com>
+// Repository: https://github.com/okalachev/flix
+
+// Fail-safe functions
+
+#define RC_LOSS_TIMEOUT 1
+#define DESCEND_TIME 10
+
+extern float controlTime;
+extern float controlRoll, controlPitch, controlThrottle, controlYaw;
+
+void failsafe() {
+	rcLossFailsafe();
+	autoFailsafe();
+}
+
+// RC loss failsafe
+void rcLossFailsafe() {
+	if (controlTime == 0) return; // no RC at all
+	if (!armed) return;
+	if (t - controlTime > RC_LOSS_TIMEOUT) {
+		descend();
+	}
+}
+
+// Smooth descend on RC lost
+void descend() {
+	mode = AUTO;
+	attitudeTarget = Quaternion();
+	thrustTarget -= dt / DESCEND_TIME;
+	if (thrustTarget < 0) {
+		thrustTarget = 0;
+		armed = false;
+	}
+}
+
+// Allow pilot to interrupt automatic flight
+void autoFailsafe() {
+	static float roll, pitch, yaw, throttle;
+	if (roll != controlRoll || pitch != controlPitch || yaw != controlYaw || abs(throttle - controlThrottle) > 0.05) {
+		// controls changed
+		if (mode == AUTO) mode = STAB; // regain control by the pilot
+	}
+	roll = controlRoll;
+	pitch = controlPitch;
+	yaw = controlYaw;
+	throttle = controlThrottle;
+}

flix/time.ino

@@ -6,7 +6,7 @@
 float loopRate; // Hz
 
 void step() {
-	double now = micros() / 1000000.0;
+	float now = micros() / 1000000.0;
 	dt = now - t;
 	t = now;
 
@@ -18,7 +18,7 @@ void step() {
 }
 
 void computeLoopRate() {
-	static double windowStart = 0;
+	static float windowStart = 0;
 	static uint32_t rate = 0;
 	rate++;
 	if (t - windowStart >= 1) { // 1 second window

flix/util.h

@@ -6,17 +6,24 @@
 #pragma once
 
 #include <math.h>
+#ifdef ESP32
 #include <soc/soc.h>
 #include <soc/rtc_cntl_reg.h>
+#endif
 
 const float ONE_G = 9.80665;
+extern float t;
 
-float mapf(long x, long in_min, long in_max, float out_min, float out_max) {
-	return (float)(x - in_min) * (out_max - out_min) / (float)(in_max - in_min) + out_min;
+float mapf(float x, float in_min, float in_max, float out_min, float out_max) {
+	return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;
 }
 
-float mapff(float x, float in_min, float in_max, float out_min, float out_max) {
-	return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;
+bool invalid(float x) {
+	return !isfinite(x);
+}
+
+bool valid(float x) {
+	return isfinite(x);
 }
 
 // Wrap angle to [-PI, PI)
@@ -32,7 +39,9 @@ float wrapAngle(float angle) {
 
 // Disable reset on low voltage
 void disableBrownOut() {
+#ifdef ESP32
 	REG_CLR_BIT(RTC_CNTL_BROWN_OUT_REG, RTC_CNTL_BROWN_OUT_ENA);
+#endif
 }
 
 // Trim and split string by spaces
@@ -44,3 +53,23 @@ void splitString(String& str, String& token0, String& token1, String& token2) {
 	token1 = strtok(NULL, " "); // String(NULL) creates empty string
 	token2 = strtok(NULL, "");
 }
+
+// Delay filter for boolean signals - ensures the signal is on for at least 'delay' seconds
+class Delay {
+public:
+	float delay;
+	float start = NAN;
+
+	Delay(float delay) : delay(delay) {}
+
+	bool update(bool on) {
+		if (!on) {
+			start = NAN;
+			return false;
+		}
+		if (isnan(start)) {
+			start = t;
+		}
+		return t - start >= delay;
+	}
+};

flix/vector.h

@@ -13,14 +13,33 @@ public:
 
 	Vector(float x, float y, float z): x(x), y(y), z(z) {};
 
-	float norm() const {
-		return sqrt(x * x + y * y + z * z);
-	}
-
 	bool zero() const {
 		return x == 0 && y == 0 && z == 0;
 	}
 
+	bool finite() const {
+		return isfinite(x) && isfinite(y) && isfinite(z);
+	}
+
+	bool valid() const {
+		return finite();
+	}
+
+	bool invalid() const {
+		return !valid();
+	}
+
+	void invalidate() {
+		x = NAN;
+		y = NAN;
+		z = NAN;
+	}
+
+
+	float norm() const {
+		return sqrt(x * x + y * y + z * z);
+	}
+
 	void normalize() {
 		float n = norm();
 		x /= n;
@@ -28,6 +47,10 @@ public:
 		z /= n;
 	}
 
+	Vector operator + (const float b) const {
+		return Vector(x + b, y + b, z + b);
+	}
+
 	Vector operator * (const float b) const {
 		return Vector(x * b, y * b, z * b);
 	}
@@ -44,6 +67,14 @@ public:
 		return Vector(x - b.x, y - b.y, z - b.z);
 	}
 
+	Vector& operator += (const Vector& b) {
+		return *this = *this + b;
+	}
+
+	Vector& operator -= (const Vector& b) {
+		return *this = *this - b;
+	}
+
 	// Element-wise multiplication
 	Vector operator * (const Vector& b) const {
 		return Vector(x * b.x, y * b.y, z * b.z);
@@ -62,10 +93,6 @@ public:
 		return !(*this == b);
 	}
 
-	bool finite() const {
-		return isfinite(x) && isfinite(y) && isfinite(z);
-	}
-
 	static float dot(const Vector& a, const Vector& b) {
 		return a.x * b.x + a.y * b.y + a.z * b.z;
 	}
@@ -74,18 +101,18 @@ public:
 		return Vector(a.y * b.z - a.z * b.y, a.z * b.x - a.x * b.z, a.x * b.y - a.y * b.x);
 	}
 
-	static float angleBetweenVectors(const Vector& a, const Vector& b) {
+	static float angleBetween(const Vector& a, const Vector& b) {
 		return acos(constrain(dot(a, b) / (a.norm() * b.norm()), -1, 1));
 	}
 
-	static Vector angularRatesBetweenVectors(const Vector& a, const Vector& b) {
+	static Vector rotationVectorBetween(const Vector& a, const Vector& b) {
 		Vector direction = cross(a, b);
 		if (direction.zero()) {
 			// vectors are opposite, return any perpendicular vector
 			return cross(a, Vector(1, 0, 0));
 		}
 		direction.normalize();
-		float angle = angleBetweenVectors(a, b);
+		float angle = angleBetween(a, b);
 		return direction * angle;
 	}
 
@@ -96,3 +123,6 @@ public:
 			p.print(z, 15);
 	}
 };
+
+Vector operator * (const float a, const Vector& b) { return b * a; }
+Vector operator + (const float a, const Vector& b) { return b + a; }

flix/wifi.ino

@@ -11,8 +11,9 @@
 
 #define WIFI_SSID "flix"
 #define WIFI_PASSWORD "flixwifi"
-#define WIFI_UDP_IP "255.255.255.255"
 #define WIFI_UDP_PORT 14550
+#define WIFI_UDP_REMOTE_PORT 14550
+#define WIFI_UDP_REMOTE_ADDR "255.255.255.255"
 
 WiFiUDP udp;
 
@@ -24,7 +25,7 @@ void setupWiFi() {
 
 void sendWiFi(const uint8_t *buf, int len) {
 	if (WiFi.softAPIP() == IPAddress(0, 0, 0, 0) && WiFi.status() != WL_CONNECTED) return;
-	udp.beginPacket(WIFI_UDP_IP, WIFI_UDP_PORT);
+	udp.beginPacket(udp.remoteIP() ? udp.remoteIP() : WIFI_UDP_REMOTE_ADDR, WIFI_UDP_REMOTE_PORT);
 	udp.write(buf, len);
 	udp.endPacket();
 }

gazebo/Arduino.h

@@ -11,6 +11,8 @@
 #include <stdio.h>
 #include <unistd.h>
 #include <sys/poll.h>
+#include <chrono>
+#include <thread>
 
 #define PI 3.1415926535897932384626433832795
 #define DEG_TO_RAD 0.017453292519943295769236907684886
@@ -52,6 +54,10 @@ public:
 		this->erase(0, this->find_first_not_of(" \t\n\r"));
 		this->erase(this->find_last_not_of(" \t\n\r") + 1);
 	}
+	void toLowerCase() {
+		std::transform(this->begin(), this->end(), this->begin(),
+			[](unsigned char c) { return std::tolower(c); });
+	}
 };
 
 class Print;
@@ -150,8 +156,11 @@ public:
 	void restart() { Serial.println("Ignore reboot in simulation"); }
 } ESP;
 
+unsigned long __delayTime = 0;
+
 void delay(uint32_t ms) {
 	std::this_thread::sleep_for(std::chrono::milliseconds(ms));
+	__delayTime += ms * 1000;
 }
 
 bool ledcAttach(uint8_t pin, uint32_t freq, uint8_t resolution) { return true; }
@@ -161,5 +170,5 @@ unsigned long __micros;
 unsigned long __resetTime = 0;
 
 unsigned long micros() {
-	return __micros + __resetTime; // keep the time monotonic
+	return __micros + __resetTime + __delayTime; // keep the time monotonic
 }

gazebo/CMakeLists.txt

@@ -1,7 +1,7 @@
 cmake_minimum_required(VERSION 3.5 FATAL_ERROR)
 project(flix_gazebo)
 
-# === gazebo plugin
+# Gazebo plugin
 find_package(gazebo REQUIRED)
 find_package(SDL2 REQUIRED)
 include_directories(${GAZEBO_INCLUDE_DIRS})

gazebo/Preferences.h

@@ -14,10 +14,9 @@ private:
 
 	void readFromFile() {
 		std::ifstream file(storagePath);
-		std::string key;
-		float value;
+		std::string key, value;
 		while (file >> key >> value) {
-			storage[key] = value;
+			storage[key] = std::stof(value); // using stof to support NaN and Infinity
 		}
 	}
 

gazebo/README.md

@@ -4,7 +4,7 @@
 
 ## Building and running
 
-See [building and running instructions](../docs/build.md#simulation).
+See [building and running instructions](../docs/usage.md#simulation).
 
 ## Code structure
 

gazebo/SBUS.h

@@ -18,6 +18,9 @@ public:
 	SBUSData data() {
 		SBUSData data;
 		joystickGet(data.ch);
+		for (int i = 0; i < 16; i++) {
+			data.ch[i] = map(data.ch[i], -32768, 32767, 1000, 2000); // convert to pulse width style
+		}
 		return data;
 	};
 };

gazebo/flix.h

@@ -12,15 +12,16 @@
 
 #define WIFI_ENABLED 1
 
-double t = NAN;
+float t = NAN;
 float dt;
 float motors[4];
-int16_t channels[16]; // raw rc channels
-float controls[16];
+float controlRoll, controlPitch, controlYaw, controlThrottle = NAN;
+float controlMode = NAN;
 Vector acc;
 Vector gyro;
 Vector rates;
 Quaternion attitude;
+bool landed;
 
 // declarations
 void step();
@@ -28,21 +29,22 @@ void computeLoopRate();
 void applyGyro();
 void applyAcc();
 void control();
-void interpretRC();
+void interpretControls();
 void controlAttitude();
-void controlRate();
+void controlRates();
 void controlTorque();
 const char* getModeName();
 void sendMotors();
 bool motorsActive();
-void testMotor(uint8_t n);
+void testMotor(int n);
 void print(const char* format, ...);
 void pause(float duration);
 void doCommand(String str, bool echo);
 void handleInput();
-void calibrateRC();
 void normalizeRC();
-void printRCCal();
+void calibrateRC();
+void calibrateRCChannel(float *channel, uint16_t zero[16], uint16_t max[16], const char *str);
+void printRCCalibration();
 void dumpLog();
 void processMavlink();
 void sendMavlink();
@@ -50,11 +52,12 @@ void sendMessage(const void *msg);
 void receiveMavlink();
 void handleMavlink(const void *_msg);
 void mavlinkPrint(const char* str);
+void sendMavlinkPrint();
 inline Quaternion fluToFrd(const Quaternion &q);
 void failsafe();
-void armingFailsafe();
 void rcLossFailsafe();
 void descend();
+void autoFailsafe();
 int parametersCount();
 const char *getParameterName(int index);
 float getParameter(int index);
@@ -67,6 +70,6 @@ void resetParameters();
 void setLED(bool on) {};
 void calibrateGyro() { print("Skip gyro calibrating\n"); };
 void calibrateAccel() { print("Skip accel calibrating\n"); };
-void printIMUCal() { print("cal: N/A\n"); };
+void printIMUCalibration() { print("cal: N/A\n"); };
 void printIMUInfo() {};
 Vector accBias, gyroBias, accScale(1, 1, 1);

gazebo/models/flix/flix.sdf

@@ -1,6 +1,7 @@
 <?xml version="1.0"?>
 <sdf version="1.5">
 	<model name="flix">
+		<plugin name="flix" filename="libflix.so"/>
 		<link name="body">
 			<inertial>
 				<mass>0.065</mass>
@@ -23,38 +24,14 @@
 				<update_rate>1000</update_rate>
 				<imu>
 					<angular_velocity>
-						<x>
-							<noise type="gaussian">
-								<stddev>0.00174533</stddev><!-- 0.1 degrees per second -->
-							</noise>
-						</x>
-						<y>
-							<noise type="gaussian">
-								<stddev>0.00174533</stddev>
-							</noise>
-						</y>
-						<z>
-							<noise type="gaussian">
-								<stddev>0.00174533</stddev>
-							</noise>
-						</z>
+						<x><noise type="gaussian"><stddev>0.00174533</stddev></noise></x><!-- 0.1 degrees per second -->
+						<y><noise type="gaussian"><stddev>0.00174533</stddev></noise></y>
+						<z><noise type="gaussian"><stddev>0.00174533</stddev></noise></z>
 					</angular_velocity>
 					<linear_acceleration>
-						<x>
-							<noise type="gaussian">
-								<stddev>0.0784</stddev><!-- 8 mg -->
-							</noise>
-						</x>
-						<y>
-							<noise type="gaussian">
-								<stddev>0.0784</stddev>
-							</noise>
-						</y>
-						<z>
-							<noise type="gaussian">
-								<stddev>0.0784</stddev>
-							</noise>
-						</z>
+						<x><noise type="gaussian"><stddev>0.0784</stddev></noise></x><!-- 8 mg -->
+						<y><noise type="gaussian"><stddev>0.0784</stddev></noise></y>
+						<z><noise type="gaussian"><stddev>0.0784</stddev></noise></z>
 					</linear_acceleration>
 				</imu>
 			</sensor>
@@ -90,6 +67,5 @@
 				<material><ambient>1 1 1 0.5</ambient><diffuse>1 1 1 0.5</diffuse></material>
 			</visual>
 		</link>
-		<plugin name="flix" filename="libflix.so"/>
 	</model>
 </sdf>

gazebo/simulator.cpp

@@ -21,7 +21,7 @@
 #include "cli.ino"
 #include "control.ino"
 #include "estimate.ino"
-#include "failsafe.ino"
+#include "safety.ino"
 #include "log.ino"
 #include "lpf.h"
 #include "mavlink.ino"
@@ -59,6 +59,7 @@ public:
 
 	void OnReset() {
 		attitude = Quaternion(); // reset estimated attitude
+		armed = false;
 		__resetTime += __micros;
 		gzmsg << "Flix plugin reset" << endl;
 	}
@@ -71,11 +72,7 @@ public:
 		gyro = Vector(imu->AngularVelocity().X(), imu->AngularVelocity().Y(), imu->AngularVelocity().Z());
 		acc = this->accFilter.update(Vector(imu->LinearAcceleration().X(), imu->LinearAcceleration().Y(), imu->LinearAcceleration().Z()));
 
-		// read rc
 		readRC();
-		controls[modeChannel] = 1; // 0 acro, 1 stab
-		controls[armedChannel] = 1; // armed
-
 		estimate();
 
 		// correct yaw to the actual yaw

gazebo/wifi.h

@@ -11,8 +11,9 @@
 #include <sys/poll.h>
 #include <gazebo/gazebo.hh>
 
-#define WIFI_UDP_PORT_LOCAL 14580
-#define WIFI_UDP_PORT_REMOTE 14550
+#define WIFI_UDP_PORT 14580
+#define WIFI_UDP_REMOTE_PORT 14550
+#define WIFI_UDP_REMOTE_ADDR "255.255.255.255"
 
 int wifiSocket;
 
@@ -21,22 +22,22 @@ void setupWiFi() {
 	sockaddr_in addr; // local address
 	addr.sin_family = AF_INET;
 	addr.sin_addr.s_addr = INADDR_ANY;
-	addr.sin_port = htons(WIFI_UDP_PORT_LOCAL);
+	addr.sin_port = htons(WIFI_UDP_PORT);
 	if (bind(wifiSocket, (sockaddr *)&addr, sizeof(addr))) {
-		gzerr << "Failed to bind WiFi UDP socket on port " << WIFI_UDP_PORT_LOCAL << std::endl;
+		gzerr << "Failed to bind WiFi UDP socket on port " << WIFI_UDP_PORT << std::endl;
 		return;
 	}
 	int broadcast = 1;
 	setsockopt(wifiSocket, SOL_SOCKET, SO_BROADCAST, &broadcast, sizeof(broadcast)); // enable broadcast
-	gzmsg << "WiFi UDP socket initialized on port " << WIFI_UDP_PORT_LOCAL << " (remote port " << WIFI_UDP_PORT_REMOTE << ")" << std::endl;
+	gzmsg << "WiFi UDP socket initialized on port " << WIFI_UDP_PORT << " (remote port " << WIFI_UDP_REMOTE_PORT << ")" << std::endl;
 }
 
 void sendWiFi(const uint8_t *buf, int len) {
 	if (wifiSocket == 0) setupWiFi();
 	sockaddr_in addr; // remote address
 	addr.sin_family = AF_INET;
-	addr.sin_addr.s_addr = INADDR_BROADCAST; // send UDP broadcast
-	addr.sin_port = htons(WIFI_UDP_PORT_REMOTE);
+	addr.sin_addr.s_addr = inet_addr(WIFI_UDP_REMOTE_ADDR);
+	addr.sin_port = htons(WIFI_UDP_REMOTE_PORT);
 	sendto(wifiSocket, buf, len, 0, (sockaddr *)&addr, sizeof(addr));
 }
 

tools/check_c_cpp_properties.py

@@ -49,6 +49,8 @@ for configuration in props['configurations']:
     print('Check configuration', configuration['name'])
 
     for include_path in configuration.get('includePath', []):
+        if include_path.startswith('/opt/') or include_path.startswith('/usr/'): # don't check non-Arduino libs
+            continue
         check_path(include_path)
 
     for forced_include in configuration.get('forcedInclude', []):

tools/cli.py

@@ -0,0 +1,13 @@
+#!/usr/bin/env python3
+
+# Remote CLI for Flix
+
+from pyflix import Flix
+
+flix = Flix()
+
+flix.on('print', lambda text: print(text, end=''))
+
+while True:
+    command = input()
+    flix.cli(command, wait_response=False)

tools/example.py

@@ -0,0 +1,39 @@
+#!/usr/bin/env python3
+
+import math
+from pyflix import Flix
+
+print('=== Connect...')
+flix = Flix()
+
+print('Connected:', flix.connected)
+print('Mode:', flix.mode)
+print('Armed:', flix.armed)
+print('Landed:', flix.landed)
+print('Rates:', *[f'{math.degrees(r):.0f}°/s' for r in flix.rates])
+print('Attitude:', *[f'{math.degrees(a):.0f}°' for a in flix.attitude_euler])
+print('Motors:', flix.motors)
+print('Acc', flix.acc)
+print('Gyro', flix.gyro)
+
+print('=== Execute commands...')
+print('> time')
+print(flix.cli('time'))
+print('> imu')
+print(flix.cli('imu'))
+
+print('=== Get parameter...')
+pitch_p = flix.get_param('PITCH_P')
+print('PITCH_P = ', pitch_p)
+
+print('=== Set parameter...')
+flix.set_param('PITCH_P', pitch_p)
+
+print('=== Wait for gyro update...')
+print('Gyro: ', flix.wait('gyro'))
+
+print('=== Wait for HEARTBEAT message...')
+print(flix.wait('mavlink.HEARTBEAT'))
+
+print('=== When until landed = False (remove drone from the surface)')
+flix.wait('landed', value=False)

tools/log.py

@@ -0,0 +1,23 @@
+#!/usr/bin/env python3
+
+# Download flight log remotely and save to file
+
+import os
+import datetime
+from pyflix import Flix
+
+DIR = os.path.dirname(os.path.realpath(__file__))
+
+flix = Flix()
+
+print('Downloading log...')
+lines = flix.cli('log').splitlines()
+
+# sort by timestamp
+header = lines.pop(0)
+lines.sort(key=lambda line: float(line.split(',')[0]))
+
+log = open(f'{DIR}/log/{datetime.datetime.now().isoformat()}.csv', 'wb')
+content = header.encode() + b'\n' + b'\n'.join(line.encode() for line in lines)
+log.write(content)
+print(f'Written {os.path.relpath(log.name, os.curdir)}')

tools/pyflix/README.md

@@ -0,0 +1,280 @@
+# Flix Python library
+
+The Flix Python library allows you to remotely connect to a Flix quadcopter. It provides access to telemetry data, supports executing CLI commands, and controlling the drone's flight.
+
+To use the library, connect to the drone's Wi-Fi. To use it with the simulator, ensure the script runs on the same local network as the simulator.
+
+## Installation
+
+If you have cloned the [repo](https://github.com/okalachev/flix), install the library from the repo:
+
+```bash
+cd /path/to/flix/repo
+pip install -e tools
+```
+
+Alternatively, install from pip:
+
+```bash
+pip install pyflix
+```
+
+## Usage
+
+The API is accessed through the `Flix` class:
+
+```python
+from flix import Flix
+flix = Flix()  # create a Flix object and wait for connection
+```
+
+### Telemetry
+
+Basic telemetry is available through object properties. The properties names generally match the corresponding variables in the firmware itself:
+
+```python
+print(flix.connected)       # True if connected to the drone
+print(flix.mode)            # current flight mode (str)
+print(flix.armed)           # True if the drone is armed
+print(flix.landed)          # True if the drone is landed
+print(flix.attitude)        # attitude quaternion [w, x, y, z]
+print(flix.attitude_euler)  # attitude as Euler angles [roll, pitch, yaw]
+print(flix.rates)           # angular rates [roll_rate, pitch_rate, yaw_rate]
+print(flix.channels)        # raw RC channels (list)
+print(flix.motors)          # motors outputs (list)
+print(flix.acc)             # accelerometer output (list)
+print(flix.gyro)            # gyroscope output (list)
+```
+
+> [!NOTE]
+> The library uses the Front-Left-Up coordinate system — the same as in the firmware. All angles are in radians.
+
+### Events
+
+The Flix object implements the *Observable* pattern, allowing to listen for events. You can subscribe to events using `on` method:
+
+```python
+flix.on('connected', lambda: print('Connected to Flix'))
+flix.on('disconnected', lambda: print('Disconnected from Flix'))
+flix.on('print', lambda text: print(f'Flix says: {text}'))
+```
+
+Unsubscribe from events using `off` method:
+
+```python
+flix.off('print')  # unsubscribe from print events
+flix.off(callback)  # unsubscribe specific callback
+```
+
+You can also wait for specific events using `wait` method. This method returns the data associated with the event:
+
+```python
+gyro = flix.wait('gyro')  # wait for gyroscope update
+attitude = flix.wait('attitude', timeout=3)  # wait for attitude update, raise TimeoutError after 3 seconds
+```
+
+The second argument (`value`) specifies a condition for filtering events. It can be either an expected value or a callable:
+
+```python
+flix.wait('armed', True)  # wait until armed
+flix.wait('armed', False)  # wait until disarmed
+flix.wait('mode', 'AUTO')  # wait until flight mode is switched to AUTO
+flix.wait('motors', lambda motors: not any(motors))  # wait until all motors stop
+flix.wait('attitude_euler', lambda att: att[0] > 0)  # wait until roll angle is positive
+```
+
+Full list of events:
+
+|Event|Description|Associated data|
+|-----|-----------|----------------|
+|`connected`|Connected to the drone||
+|`disconnected`|Connection is lost||
+|`armed`|Armed state update|Armed state (*bool*)|
+|`mode`|Flight mode update|Flight mode (*str*)|
+|`landed`|Landed state update|Landed state (*bool*)|
+|`print`|The drone sends text to the console|Text|
+|`attitude`|Attitude update|Attitude quaternion (*list*)|
+|`attitude_euler`|Attitude update|Euler angles (*list*)|
+|`rates`|Angular rates update|Angular rates (*list*)|
+|`channels`|Raw RC channels update|Raw RC channels (*list*)|
+|`motors`|Motors outputs update|Motors outputs (*list*)|
+|`acc`|Accelerometer update|Accelerometer output (*list*)|
+|`gyro`|Gyroscope update|Gyroscope output (*list*)|
+|`mavlink`|Received MAVLink message|Message object|
+|`mavlink.<message_name>`|Received specific MAVLink message|Message object|
+|`mavlink.<message_id>`|Received specific MAVLink message|Message object|
+|`value`|Named value update (see below)|Name, value|
+|`value.<name>`|Specific named value update (see bellow)|Value|
+
+> [!NOTE]
+> Update events trigger on every new data from the drone, and do not mean the value is changed.
+
+### Common methods
+
+Get and set firmware parameters using `get_param` and `set_param` methods:
+
+```python
+pitch_p = flix.get_param('PITCH_P')  # get parameter value
+flix.set_param('PITCH_P', 5)         # set parameter value
+```
+
+Execute CLI commands using `cli` method. This method returns command response:
+
+```python
+imu = flix.cli('imu')    # get detailed IMU data
+time = flix.cli('time')  # get detailed time data
+flix.cli('reboot')       # reboot the drone
+```
+
+> [!TIP]
+> Use `help` command to get the list of available commands.
+
+You can arm and disarm the drone using `set_armed` method (warning: the drone will fall if disarmed in the air):
+
+```python
+flix.set_armed(True)   # arm the drone
+flix.set_armed(False)  # disarm the drone
+```
+
+You can imitate pilot's controls using `set_controls` method:
+
+```python
+flix.set_controls(roll=0, pitch=0, yaw=0, throttle=0.6)
+```
+
+> [!WARNING]
+> This method **is not intended for automatic flights**, only for adding support for a custom pilot input device.
+
+### Automatic flight
+
+To perform automatic flight, switch the mode to *AUTO*, either from the remote control, or from the code:
+
+```python
+flix.set_mode('AUTO')
+```
+
+In this mode you can set flight control targets. Setting attitude target:
+
+```python
+flix.set_attitude([0.1, 0.2, 0.3], 0.6)  # set target roll, pitch, yaw and thrust
+flix.set_attitude([1, 0, 0, 0], 0.6)  # set target attitude quaternion and thrust
+```
+
+Setting angular rates target:
+
+```python
+flix.set_rates([0.1, 0.2, 0.3], 0.6)  # set target roll rate, pitch rate, yaw rate and thrust
+```
+
+You also can control raw motors outputs directly:
+
+```python
+flix.set_motors([0.5, 0.5, 0.5, 0.5])  # set motors outputs in range [0, 1]
+```
+
+In *AUTO* mode, the drone will arm automatically if the thrust is greater than zero, and disarm if thrust is zero. Therefore, to disarm the drone, set thrust to zero:
+
+```python
+flix.set_attitude([0, 0, 0], 0)  # disarm the drone
+```
+
+The following methods are in development and are not functional yet:
+
+* `set_position` — set target position.
+* `set_velocity` — set target velocity.
+
+To exit from *AUTO* mode move control sticks and the drone will switch to *STAB* mode.
+
+## Usage alongside QGroundControl
+
+You can use the Flix library alongside the QGroundControl app, using proxy mode. To do that:
+
+1. Run proxy for `pyflix` and QGroundControl in background:
+
+   ```bash
+   flix-proxy
+   ```
+
+2. Go to QGroundControl settings ⇒ *Comm Links*.
+3. Add new link with the following settings:
+   * *Name*: Proxy
+   * *Automatically Connect on Start*: ✓
+   * *Type*: UDP
+   * *Port*: 14560
+4. Restart QGroundControl.
+
+<img src="../../docs/img/qgc-proxy.png" width="300">
+
+Now you can run `pyflix` scripts and QGroundControl simultaneously.
+
+## Tools
+
+The following scripts demonstrate how to use the library:
+
+* [`cli.py`](../cli.py) — remote access to the drone's command line interface.
+* [`log.py`](../log.py) — download flight logs from the drone.
+* [`example.py`](../example.py) — a simple example, prints telemetry data and waits for events.
+
+## Advanced usage
+
+### MAVLink
+
+You can access the most recently received messages using `messages` property:
+
+```python
+print(flix.messages.get('HEARTBEAT'))  # print the latest HEARTBEAT message
+```
+
+You can wait for a specific message using `wait` method:
+
+```python
+heartbeat = flix.wait('mavlink.HEARTBEAT')
+```
+
+You can send raw messages using `mavlink` property:
+
+```python
+from pymavlink.dialects.v20 import common as mavlink
+
+flix.mavlink.heartbeat_send(mavlink.MAV_TYPE_GCS, mavlink.MAV_AUTOPILOT_INVALID,
+                            mavlink.MAV_MODE_FLAG_CUSTOM_MODE_ENABLED, 0, 0)
+```
+
+### Named values
+
+You can pass arbitrary named values from the firmware to the Python script using `NAMED_VALUE_FLOAT`, `NAMED_VALUE_INT`, `DEBUG`, `DEBUG_VECT`, and `DEBUG_FLOAT_ARRAY` MAVLink messages.
+
+All these named values will appear in the `values` dictionary:
+
+```python
+print(flix.values['some_value'])
+print(flix.values['some_vector'])
+```
+
+You can send values from the firmware like this (`mavlink.ino`):
+
+```cpp
+// Send float named value
+mavlink_msg_named_value_float_pack(SYSTEM_ID, MAV_COMP_ID_AUTOPILOT1, &msg, t, "loop_rate", loopRate);
+sendMessage(&msg);
+
+// Send vector named value
+mavlink_msg_debug_vect_pack(SYSTEM_ID, MAV_COMP_ID_AUTOPILOT1, &msg, "gyro_bias", t, gyroBias.x, gyroBias.y, gyroBias.z);
+sendMessage(&msg);
+```
+
+### Logging
+
+You can control Flix library verbosity using Python's `logging` module:
+
+```python
+import logging
+
+logger = logging.getLogger('flix')
+logger.setLevel(logging.DEBUG)  # be more verbose
+logger.setLevel(logging.WARNING)  # be less verbose
+```
+
+## Stability
+
+The library is in development stage. The API is not stable.

tools/pyflix/__init__.py

@@ -0,0 +1 @@
+from .flix import Flix

tools/pyflix/flix.py

@@ -0,0 +1,379 @@
+# Copyright (c) 2025 Oleg Kalachev <okalachev@gmail.com>
+# Repository: https://github.com/okalachev/flix
+
+"""Python API for Flix drone."""
+
+import os
+import time
+from queue import Queue, Empty
+from typing import Optional, Callable, List, Dict, Any, Union, Sequence
+import logging
+import errno
+from threading import Thread, Timer
+from pymavlink import mavutil
+from pymavlink.quaternion import Quaternion
+from pymavlink.dialects.v20 import common as mavlink
+
+logger = logging.getLogger('flix')
+if not logger.hasHandlers():
+    handler = logging.StreamHandler()
+    handler.setFormatter(logging.Formatter('%(name)s - %(levelname)s - %(message)s'))
+    logger.addHandler(handler)
+    logger.setLevel(logging.INFO)
+
+class Flix:
+    connected: bool = False
+    mode: str = ''
+    armed: bool = False
+    landed: bool = False
+    attitude: List[float]
+    attitude_euler: List[float]  # roll, pitch, yaw
+    rates: List[float]
+    channels: List[int]
+    motors: List[float]
+    acc: List[float]
+    gyro: List[float]
+
+    system_id: int
+    messages: Dict[str, Dict[str, Any]]  # MAVLink messages storage
+    values: Dict[Union[str, int], Union[float, List[float]]]  # named values
+
+    _connection_timeout = 3
+    _print_buffer: str = ''
+    _modes = ['MANUAL', 'ACRO', 'STAB', 'AUTO']
+
+    def __init__(self, system_id: int=1, wait_connection: bool=True):
+        if not (0 <= system_id < 256):
+            raise ValueError('system_id must be in range [0, 255]')
+        self._setup_mavlink()
+        self.system_id = system_id
+        self._init_state()
+        try:
+            # Direct connection
+            logger.debug('Listening on port 14550')
+            self.connection: mavutil.mavfile = mavutil.mavlink_connection('udpin:0.0.0.0:14550', source_system=255)  # type: ignore
+        except OSError as e:
+            if e.errno != errno.EADDRINUSE:
+                raise
+            # Port busy - using proxy
+            logger.debug('Listening on port 14555 (proxy)')
+            self.connection: mavutil.mavfile = mavutil.mavlink_connection('udpin:0.0.0.0:14555', source_system=254)  # type: ignore
+        self.connection.target_system = system_id
+        self.mavlink: mavlink.MAVLink = self.connection.mav
+        self._event_listeners: Dict[str, List[Callable[..., Any]]] = {}
+        self._disconnected_timer = Timer(0, self._disconnected)
+        self._reader_thread = Thread(target=self._read_mavlink, daemon=True)
+        self._reader_thread.start()
+        self._heartbeat_thread = Thread(target=self._send_heartbeat, daemon=True)
+        self._heartbeat_thread.start()
+        if wait_connection:
+            self.wait('mavlink.HEARTBEAT')
+            time.sleep(0.2) # give some time to receive initial state
+
+    def _init_state(self):
+        self.attitude = [1, 0, 0, 0]
+        self.attitude_euler = [0, 0, 0]
+        self.rates = [0, 0, 0]
+        self.channels = [0, 0, 0, 0, 0, 0, 0, 0]
+        self.motors = [0, 0, 0, 0]
+        self.acc = [0, 0, 0]
+        self.gyro = [0, 0, 0]
+        self.messages = {}
+        self.values = {}
+
+    def on(self, event: str, callback: Callable):
+        event = event.lower()
+        if event not in self._event_listeners:
+            self._event_listeners[event] = []
+        self._event_listeners[event].append(callback)
+
+    def off(self, event_or_callback: Union[str, Callable]):
+        if isinstance(event_or_callback, str):
+            event = event_or_callback.lower()
+            if event in self._event_listeners:
+                del self._event_listeners[event]
+        else:
+            for event in self._event_listeners:
+                if event_or_callback in self._event_listeners[event]:
+                    self._event_listeners[event].remove(event_or_callback)
+
+    def _trigger(self, event: str, *args):
+        event = event.lower()
+        for callback in self._event_listeners.get(event, []):
+            try:
+                callback(*args)
+            except Exception as e:
+                logger.error(f'Error in event listener for event {event}: {e}')
+
+    def wait(self, event: str, value: Union[Any, Callable[..., bool]] = lambda *args: True, timeout=None) -> Any:
+        """Wait for an event"""
+        event = event.lower()
+        q = Queue()
+        def callback(*args):
+            if len(args) == 0:
+                result = None
+            elif len(args) == 1:
+                result = args[0]
+            else:
+                result = args
+            if callable(value) and value(*args):
+                q.put_nowait(result)
+            elif value == result:
+                q.put_nowait(result)
+        self.on(event, callback)
+        try:
+            return q.get(timeout=timeout)
+        except Empty:
+            raise TimeoutError
+        finally:
+            self.off(callback)
+
+    @staticmethod
+    def _setup_mavlink():
+        # otherwise it will use MAVLink 1.0 until connected
+        os.environ['MAVLINK20'] = '1'
+        mavutil.set_dialect('common')
+
+    def _read_mavlink(self):
+        while True:
+            try:
+                msg: Optional[mavlink.MAVLink_message] = self.connection.recv_match(blocking=True)
+                if msg is None:
+                    continue
+                self._connected()
+                msg_dict = msg.to_dict()
+                msg_dict['_timestamp'] = time.time()  # add timestamp
+                self.messages[msg.get_type()] = msg_dict
+                self._trigger('mavlink', msg)
+                self._trigger(f'mavlink.{msg.get_type()}', msg)  # trigger mavlink.<message_type>
+                self._trigger(f'mavlink.{msg.get_msgId()}', msg)  # trigger mavlink.<message_id>
+                self._handle_mavlink_message(msg)
+
+            except Exception as e:
+                logger.error(f'Error reading MAVLink message: {e}')
+
+    def _handle_mavlink_message(self, msg: mavlink.MAVLink_message):
+        if isinstance(msg, mavlink.MAVLink_heartbeat_message):
+            self.mode = self._modes[msg.custom_mode] if msg.custom_mode < len(self._modes) else f'UNKNOWN({msg.custom_mode})'
+            self.armed = msg.base_mode & mavlink.MAV_MODE_FLAG_SAFETY_ARMED != 0
+            self._trigger('mode', self.mode)
+            self._trigger('armed', self.armed)
+
+        if isinstance(msg, mavlink.MAVLink_extended_sys_state_message):
+            self.landed = msg.landed_state == mavlink.MAV_LANDED_STATE_ON_GROUND
+            self._trigger('landed', self.landed)
+
+        if isinstance(msg, mavlink.MAVLink_attitude_quaternion_message):
+            self.attitude = self._mavlink_to_flu([msg.q1, msg.q2, msg.q3, msg.q4])
+            self.rates = self._mavlink_to_flu([msg.rollspeed, msg.pitchspeed, msg.yawspeed])
+            self.attitude_euler = list(Quaternion(self.attitude).euler)  # type: ignore
+            self._trigger('attitude', self.attitude)
+            self._trigger('attitude_euler', self.attitude_euler)
+
+        if isinstance(msg, mavlink.MAVLink_rc_channels_raw_message):
+            self.channels = [msg.chan1_raw, msg.chan2_raw, msg.chan3_raw, msg.chan4_raw,
+                             msg.chan5_raw, msg.chan6_raw, msg.chan7_raw, msg.chan8_raw]
+            self._trigger('channels', self.channels)
+
+        if isinstance(msg, mavlink.MAVLink_actuator_control_target_message):
+            self.motors = msg.controls[:4]  # type: ignore
+            self._trigger('motors', self.motors)
+
+        # TODO: to be removed: the old way of passing motor outputs
+        if isinstance(msg, mavlink.MAVLink_actuator_output_status_message):
+            self.motors = msg.actuator[:4]  # type: ignore
+            self._trigger('motors', self.motors)
+
+        if isinstance(msg, mavlink.MAVLink_scaled_imu_message):
+            self.acc = self._mavlink_to_flu([msg.xacc / 1000, msg.yacc / 1000, msg.zacc / 1000])
+            self.gyro = self._mavlink_to_flu([msg.xgyro / 1000, msg.ygyro / 1000, msg.zgyro / 1000])
+            self._trigger('acc', self.acc)
+            self._trigger('gyro', self.gyro)
+
+        if isinstance(msg, mavlink.MAVLink_serial_control_message):
+            # new chunk of data
+            text = bytes(msg.data)[:msg.count].decode('utf-8', errors='ignore')
+            logger.debug(f'Console: {repr(text)}')
+            self._trigger('print', text)
+            self._print_buffer += text
+            if msg.flags & mavlink.SERIAL_CONTROL_FLAG_MULTI == 0:
+                # last chunk
+                self._trigger('print_full', self._print_buffer)
+                self._print_buffer = ''
+
+        if isinstance(msg, mavlink.MAVLink_statustext_message):
+            logger.info(f'Flix #{msg.get_srcSystem()}: {msg.text}')
+            self._trigger('status', msg.text)
+
+        if isinstance(msg, (mavlink.MAVLink_named_value_float_message, mavlink.MAVLink_named_value_int_message)):
+            self.values[msg.name] = msg.value
+            self._trigger('value', msg.name, msg.value)
+            self._trigger(f'value.{msg.name}', msg.value)
+
+        if isinstance(msg, mavlink.MAVLink_debug_message):
+            self.values[msg.ind] = msg.value
+            self._trigger('value', msg.ind, msg.value)
+            self._trigger(f'value.{msg.ind}', msg.value)
+
+        if isinstance(msg, mavlink.MAVLink_debug_vect_message):
+            self.values[msg.name] = [msg.x, msg.y, msg.z]
+            self._trigger('value', msg.name, self.values[msg.name])
+            self._trigger(f'value.{msg.name}', self.values[msg.name])
+
+        if isinstance(msg, mavlink.MAVLink_debug_float_array_message):
+            self.values[msg.name] = list(msg.data)
+            self._trigger('value', msg.name, self.values[msg.name])
+            self._trigger(f'value.{msg.name}', self.values[msg.name])
+
+    def _send_heartbeat(self):
+        while True:
+            self.mavlink.heartbeat_send(mavlink.MAV_TYPE_GCS, mavlink.MAV_AUTOPILOT_INVALID, 0, 0, 0)
+            time.sleep(1)
+
+    @staticmethod
+    def _mavlink_to_flu(v: List[float]) -> List[float]:
+        if len(v) == 3:  # vector
+            return [v[0], -v[1], -v[2]]
+        elif len(v) == 4:  # quaternion
+            return [v[0], v[1], -v[2], -v[3]]
+        else:
+            raise ValueError(f'List must have 3 (vector) or 4 (quaternion) elements')
+
+    @staticmethod
+    def _flu_to_mavlink(v: List[float]) -> List[float]:
+        return Flix._mavlink_to_flu(v)
+
+    def _command_send(self, command: int, params: Sequence[float]):
+        if len(params) != 7:
+            raise ValueError('Command must have 7 parameters')
+        for attempt in range(3):
+            try:
+                logger.debug(f'Send command {command} with params {params} (attempt #{attempt + 1})')
+                self.mavlink.command_long_send(self.system_id, 0, command, 0, *params)  # type: ignore
+                self.wait('mavlink.COMMAND_ACK', value=lambda msg: msg.command == command and msg.result == mavlink.MAV_RESULT_ACCEPTED, timeout=0.1)
+                return
+            except TimeoutError:
+                continue
+        raise RuntimeError(f'Failed to send command {command} after 3 attempts')
+
+    def _connected(self):
+        # Reset disconnection timer
+        self._disconnected_timer.cancel()
+        self._disconnected_timer = Timer(self._connection_timeout, self._disconnected)
+        self._disconnected_timer.start()
+
+        if not self.connected:
+            logger.info('Connection is established')
+            self.connected = True
+            self._trigger('connected')
+
+    def _disconnected(self):
+        logger.info('Connection is lost')
+        self.connected = False
+        self._trigger('disconnected')
+
+    def get_param(self, name: str) -> float:
+        if len(name.encode('ascii')) > 16:
+            raise ValueError('Parameter name must be 16 characters or less')
+        for attempt in range(3):
+            try:
+                logger.debug(f'Get param {name} (attempt #{attempt + 1})')
+                self.mavlink.param_request_read_send(self.system_id, 0, name.encode('ascii'), -1)
+                msg: mavlink.MAVLink_param_value_message = \
+                    self.wait('mavlink.PARAM_VALUE', value=lambda msg: msg.param_id == name, timeout=0.1)
+                return msg.param_value
+            except TimeoutError:
+                continue
+        raise RuntimeError(f'Failed to get parameter {name} after 3 attempts')
+
+    def set_param(self, name: str, value: float):
+        if len(name.encode('ascii')) > 16:
+            raise ValueError('Parameter name must be 16 characters or less')
+        for attempt in range(3):
+            try:
+                logger.debug(f'Set param {name} to {value} (attempt #{attempt + 1})')
+                self.mavlink.param_set_send(self.system_id, 0, name.encode('ascii'), value, mavlink.MAV_PARAM_TYPE_REAL32)
+                self.wait('mavlink.PARAM_VALUE', value=lambda msg: msg.param_id == name, timeout=0.1)
+                return
+            except TimeoutError:
+                # on timeout try again
+                continue
+        raise RuntimeError(f'Failed to set parameter {name} to {value} after 3 attempts')
+
+    def set_mode(self, mode: Union[str, int]):
+        if isinstance(mode, str):
+            mode = self._modes.index(mode.upper())
+        self._command_send(mavlink.MAV_CMD_DO_SET_MODE, (0, mode, 0, 0, 0, 0, 0))
+
+    def set_armed(self, armed: bool):
+        self._command_send(mavlink.MAV_CMD_COMPONENT_ARM_DISARM, (1 if armed else 0, 0, 0, 0, 0, 0, 0))
+
+    def set_position(self, position: List[float], yaw: Optional[float] = None, wait: bool = False, tolerance: float = 0.1):
+        raise NotImplementedError('Position control is not implemented yet')
+
+    def set_velocity(self, velocity: List[float], yaw: Optional[float] = None):
+        raise NotImplementedError('Velocity control is not implemented yet')
+
+    def set_attitude(self, attitude: List[float], thrust: float):
+        if len(attitude) == 3:
+            attitude = Quaternion([attitude[0], attitude[1], attitude[2]]).q  # type: ignore
+        elif len(attitude) != 4:
+            raise ValueError('Attitude must be [roll, pitch, yaw] or [w, x, y, z] quaternion')
+        if not (0 <= thrust <= 1):
+            raise ValueError('Thrust must be in range [0, 1]')
+        attitude = self._flu_to_mavlink(attitude)
+        for _ in range(2): # duplicate to ensure delivery
+            self.mavlink.set_attitude_target_send(0, self.system_id, 0, 0,
+                [attitude[0], attitude[1], attitude[2], attitude[3]],
+                0, 0, 0, thrust)
+
+    def set_rates(self, rates: List[float], thrust: float):
+        if len(rates) != 3:
+            raise ValueError('Rates must be [roll_rate, pitch_rate, yaw_rate]')
+        if not (0 <= thrust <= 1):
+            raise ValueError('Thrust must be in range [0, 1]')
+        rates = self._flu_to_mavlink(rates)
+        for _ in range(2):  # duplicate to ensure delivery
+            self.mavlink.set_attitude_target_send(0, self.system_id, 0,
+                mavlink.ATTITUDE_TARGET_TYPEMASK_ATTITUDE_IGNORE,
+                [1, 0, 0, 0],
+                rates[0], rates[1], rates[2], thrust)
+
+    def set_motors(self, motors: List[float]):
+        if len(motors) != 4:
+            raise ValueError('motors must have 4 values')
+        if not all(0 <= m <= 1 for m in motors):
+            raise ValueError('motors must be in range [0, 1]')
+        for _ in range(2):  # duplicate to ensure delivery
+            self.mavlink.set_actuator_control_target_send(int(time.time() * 1000000), 0, self.system_id, 0, motors + [0] * 4)  # type: ignore
+
+    def set_controls(self, roll: float, pitch: float, yaw: float, throttle: float):
+        """Send pilot's controls. Warning: not intended for automatic control"""
+        if not (-1 <= roll <= 1 and -1 <= pitch <= 1 and -1 <= yaw <= 1):
+            raise ValueError('roll, pitch, yaw must be in range [-1, 1]')
+        if not 0 <= throttle <= 1:
+            raise ValueError('throttle must be in range [0, 1]')
+        self.mavlink.manual_control_send(self.system_id, int(pitch * 1000), int(roll * 1000), int(throttle * 1000), int(yaw * 1000), 0)  # type: ignore
+
+    def cli(self, cmd: str, wait_response: bool = True) -> str:
+        cmd = cmd.strip()
+        if cmd == 'reboot':
+            wait_response = False  # reboot command doesn't respond
+        cmd_bytes = (cmd + '\n').encode('utf-8')
+        if len(cmd_bytes) > 70:
+            raise ValueError(f'Command is too long: {len(cmd_bytes)} > 70')
+        cmd_bytes = cmd_bytes.ljust(70, b'\0')
+        response_prefix = f'> {cmd}\n'
+        for attempt in range(3):
+            logger.debug(f'Send command {cmd} (attempt #{attempt + 1})')
+            try:
+                self.mavlink.serial_control_send(0, 0, 0, 0, len(cmd_bytes), cmd_bytes)
+                if not wait_response:
+                    return ''
+                timeout = 0.1
+                if cmd == 'log': timeout = 10 # log download may take more time
+                response = self.wait('print_full', timeout=timeout, value=lambda text: text.startswith(response_prefix))
+                return response[len(response_prefix):].strip()
+            except TimeoutError:
+                continue
+        raise RuntimeError(f'Failed to send command {cmd} after 3 attempts')

tools/pyflix/proxy.py

@@ -0,0 +1,40 @@
+#!/usr/bin/env python3
+
+"""Proxy for running pyflix library alongside QGroundControl app."""
+
+import socket
+
+LOCAL = ('0.0.0.0', 14550)  # from Flix
+TARGETS = (
+    ('127.0.0.1', 14560),  # to QGroundControl
+    ('127.0.0.1', 14555),  # to pyflix
+)
+
+def main():
+    sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+    sock.bind(LOCAL)
+
+    source_addr = None
+    packets = 0
+
+    print('Proxy started - run QGroundControl')
+
+    while True:
+        data, addr = sock.recvfrom(1024)  # read entire UDP packet
+        if addr in TARGETS:  # packet from target
+            if source_addr is None:
+                continue
+            try:
+                sock.sendto(data, source_addr)
+                packets += 1
+            except: pass
+        else:  # packet from source
+            source_addr = addr
+            for target in TARGETS:
+                sock.sendto(data, target)
+                packets += 1
+
+        print(f'\rPackets: {packets}', end='')
+
+if __name__ == '__main__':
+    main()

tools/pyproject.toml

@@ -0,0 +1,29 @@
+[project]
+name = "pyflix"
+version = "0.9"
+description = "Python API for Flix drone"
+authors = [{ name="Oleg Kalachev", email="okalachev@gmail.com" }]
+license = "MIT"
+readme = "pyflix/README.md"
+requires-python = ">=3.8"
+dependencies = [
+    "pymavlink",
+]
+
+[project.scripts]
+flix-proxy = "pyflix.proxy:main"
+
+[build-system]
+requires = ["setuptools>=61.0"]
+build-backend = "setuptools.build_meta"
+
+[tool.setuptools]
+packages = ["pyflix"]
+
+[tool.setuptools.package-data]
+pyflix = ["README.md"]
+
+[project.urls]
+Homepage = "https://github.com/okalachev/flix/tree/master/tools/pyflix"
+Repository = "https://github.com/okalachev/flix"
+Issues = "https://github.com/okalachev/flix/issues"