Add new user builds, add school 548 course overview

+ minor doc fixes.

.github/workflows/build.yml

@@ -15,8 +15,17 @@ 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
@@ -46,15 +55,25 @@ 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
@@ -32,7 +32,7 @@ simulator: build_simulator
 	gazebo --verbose ${CURDIR}/gazebo/flix.world
 
 log:
-	PORT=$(PORT) tools/grab_log.py
+	tools/log.py
 
 plot:
 	plotjuggler -d $(shell ls -t tools/log/*.csv | head -n1)

README.md

@@ -1,6 +1,6 @@
 # Flix
 
-**Flix** (*flight + X*) — making an open source ESP32-based quadcopter from scratch.
+**Flix** (*flight + X*) — open source ESP32-based quadcopter made from scratch.
 
 <table>
   <tr>
@@ -15,51 +15,66 @@
 
 ## 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).
+## Documentation
 
-## Components (version 1)
+1. [Assembly instructions](docs/assembly.md).
+2. [Usage: build, setup and flight](docs/usage.md).
+3. [Simulation](gazebo/README.md).
+4. [Python library](tools/pyflix/README.md).
+
+Additional articles:
+
+* [User builds gallery](docs/user.md).
+* [Firmware architectural overview](docs/firmware.md).
+* [Troubleshooting](docs/troubleshooting.md).
+* [Log analysis](docs/log.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|
-|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|
+|IMU (and barometer¹) 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|
+|Boost converter (optional, for more stable power supply)|5V output|<img src="docs/img/buck-boost.jpg" width=100>|1|
+|Motor|8520 3.7V brushed motor.<br>Motor with exact 3.7V voltage is needed, not ranged working voltage (3.7V — 6V).<br>Make sure the motor shaft diameter and propeller hole diameter match!|<img src="docs/img/motor.jpeg" width=100>|4|
+|Propeller|55 mm (alternatively 65 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|
 |Pull-down resistor|10 kΩ|<img src="docs/img/resistor10k.jpg" width=100>|4|
 |3.7V Li-Po battery|LW 952540 (or any compatible by the size)|<img src="docs/img/battery.jpg" width=100>|1|
@@ -67,18 +82,17 @@ 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 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|
-|*RC receiver (optional)*|*DF500 or other⁵*|<img src="docs/img/rx.jpg" width=100>|1|
+|Frame main part|3D printed²: [`stl`](docs/assets/flix-frame-1.1.stl) [`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: [`stl`](docs/assets/esp32-holder.stl) [`step`](docs/assets/esp32-holder.step)|<img src="docs/img/esp32-holder.jpg" width=100>|1|
+|Washer for IMU board mounting|3D printed: [`stl`](docs/assets/washer-m3.stl) [`step`](docs/assets/washer-m3.step)|<img src="docs/img/washer-m3.jpg" width=100>|2|
+|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 other³*|<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>
-*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.*
+*¹ — barometer is not used for now.*<br>
+*² — this frame is optimized for GY-91 board, if using other, the board mount holes positions should be modified.*<br>
+*³ — you also may use any transmitter-receiver pair with SBUS interface.*
 
 Tools required for assembly:
 
@@ -88,13 +102,15 @@ Tools required for assembly:
 * Screwdrivers.
 * Multimeter.
 
-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)).
+Feel free to modify the design and or code, and create your own improved versions. 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 elements are optional).*
 
 Motor connection scheme:
 
@@ -102,8 +118,6 @@ Motor connection scheme:
 
 You can see a user-contributed [variant of complete circuit diagram](https://miro.com/app/board/uXjVN-dTjoo=/?moveToWidget=3458764612338222067&cot=14) of the drone.
 
-See [assembly guide](docs/assembly.md) for instructions on assembling the drone.
-
 ### Notes
 
 * Power ESP32 Mini with Li-Po battery using VCC (+) and GND (-) pins.
@@ -121,14 +135,15 @@ See [assembly guide](docs/assembly.md) for instructions on assembling the drone.
 * Solder pull-down resistors to the MOSFETs.
 * Connect the motors to the ESP32 Mini using MOSFETs, by following scheme:
 
-  |Motor|Position|Direction|Wires|GPIO|
-  |-|-|-|-|-|
-  |Motor 0|Rear left|Counter-clockwise|Black & White|GPIO12 (*TDI*)|
-  |Motor 1|Rear right|Clockwise|Blue & Red|GPIO13 (*TCK*)|
-  |Motor 2|Front right|Counter-clockwise|Black & White|GPIO14 (*TMS*)|
-  |Motor 3|Front left|Clockwise|Blue & Red|GPIO15 (*TD0*)|
+  |Motor|Position|Direction|Prop type|Motor wires|GPIO|
+  |-|-|-|-|-|-|
+  |Motor 0|Rear left|Counter-clockwise|B|Black & White|GPIO12 (*TDI*)|
+  |Motor 1|Rear right|Clockwise|A|Blue & Red|GPIO13 (*TCK*)|
+  |Motor 2|Front right|Counter-clockwise|B|Black & White|GPIO14 (*TMS*)|
+  |Motor 3|Front left|Clockwise|A|Blue & Red|GPIO15 (*TD0*)|
 
-  Counter-clockwise motors have black and white wires and clockwise motors have blue and red wires.
+  Clockwise motors have blue & red wires and correspond to propeller type A (marked on the propeller).
+  Counter-clockwise motors have black & white wires correspond to propeller type B.
 
 * Optionally connect the RC receiver to the ESP32's UART2:
 
@@ -136,28 +151,18 @@ See [assembly guide](docs/assembly.md) for instructions on assembling the drone.
   |-|-|
   |GND|GND|
   |VIN|VCC (or 3.3V depending on the receiver)|
-  |Signal (TX)|GPIO4⁶|
+  |Signal (TX)|GPIO4¹|
 
-*⁶ — UART2 RX pin was [changed](https://docs.espressif.com/projects/arduino-esp32/en/latest/migration_guides/2.x_to_3.0.html#id14) to GPIO4 in Arduino ESP32 core 3.0.*
+*¹ — UART2 RX pin was [changed](https://docs.espressif.com/projects/arduino-esp32/en/latest/migration_guides/2.x_to_3.0.html#id14) to GPIO4 in Arduino ESP32 core 3.0.*
 
-### IMU placement
+## Resources
 
-Default IMU orientation in the code is **LFD** (Left-Forward-Down):
+* Telegram channel on developing the drone and the flight controller (in Russian): https://t.me/opensourcequadcopter.
+* 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/.
 
-<img src="docs/img/gy91-lfd.svg" width=400 alt="GY-91 axes">
+## Disclaimer
 
-In case of using other IMU orientation, modify the `rotateIMU` function in the `imu.ino` file.
+This is a 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.
 
-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.
-
-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/.
+⚠️ 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/assembly.md

@@ -27,3 +27,27 @@ Soldered components ([schematics variant](https://miro.com/app/board/uXjVN-dTjoo
 <br>Assembled drone:
 
 <img src="img/assembly/7.jpg" width=600>
+
+## Motor directions
+
+> [!WARNING]
+> The drone above is an early build, and it has **inversed** motor directions scheme. The photos only illustrate the assembly process in general.
+
+Use standard motor directions scheme:
+
+<img src="img/motors.svg" width=200>
+
+Motors connection table:
+
+|Motor|Position|Direction|Prop type|Motor wires|GPIO|
+|-|-|-|-|-|-|
+|Motor 0|Rear left|Counter-clockwise|B|Black & White|GPIO12 (*TDI*)|
+|Motor 1|Rear right|Clockwise|A|Blue & Red|GPIO13 (*TCK*)|
+|Motor 2|Front right|Counter-clockwise|B|Black & White|GPIO14 (*TMS*)|
+|Motor 3|Front left|Clockwise|A|Blue & Red|GPIO15 (*TD0*)|
+
+## Motors tightening
+
+Motors should be installed very tightly — any vibration may lead to bad attitude estimation and unstable flight. If motors are loose, use tiny tape pieces to fix them tightly as shown below:
+
+<img src="img/motor-tape.jpg" width=600>

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`, `controlYaw`, `controlThrottle`, `controlMode` *(float)* — команды управления от пилота, в диапазоне [-1, 1].
+* `motors` *(float[4])* — 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 +1,2 @@
-# 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.
+<!-- markdownlint-disable MD041 -->
+Build instructions are moved to [usage article](usage.md).

docs/firmware.md

@@ -1,37 +1,67 @@
 # 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. The dataflow goes through global variables, including:
 
-* `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`, `controlYaw`, `controlThrottle`, `controlMode` *(float)* — pilot control inputs, range [-1, 1].
+* `motors` *(float[4])* — 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.
 
-* [`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.
+* [`cli.ino`](../flix/cli.ino) — serial and MAVLink console.
 
-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.
 
-## Building
+### Control subsystem
 
-See build instructions in [build.md](build.md).
+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 handled in `controlAttitude()`, `controlRates()`, `controlTorque()` functions. Each function may be skipped if the corresponding control 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.
+
+### Console
+
+To write into the console, `print()` function is used. This function sends data both to the Serial console and to the MAVLink console (which can be accessed wirelessly in QGroundControl). The function supports formatting:
+
+```cpp
+print("Test value: %.2f\n", testValue);
+```
+
+In order to add a console command, modify the `doCommand()` function in `cli.ino` file.
+
+## Building the firmware
+
+See build instructions in [usage.md](usage.md).

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docs/log.md

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 Flix quadcopter uses RAM to store flight log data. The default log capacity is 10 seconds at 100 Hz. This configuration can be adjusted in the `log.ino` file.
 
-To perform log analysis, you need to download the log right after the flight without powering off the drone. Then you can use several tools to analyze the log data.
-
-## Log download
-
-To download the log, connect the ESP32 using USB right after the flight and run the following command:
+To perform log analysis, you need to download the flight log. To to that, ensure you're connected to the drone using Wi-Fi and run the following command:
 
 ```bash
 make log

docs/rotation.css

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+	.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 +32,8 @@ 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 propeller directions are correct**. Make sure your propeller types (A or B) are installed as on the picture:
+  <img src="img/user/peter_ukhov-2/1.jpg" width="200">
+* **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 +1,238 @@
+# Usage: build, setup and flight
+
+To fly Flix quadcopter, you need to build the firmware, upload it to the ESP32 board, and set up the drone for flight.
+
+To get the firmware sources, clone the repository using git:
+
+```bash
+git clone https://github.com/okalachev/flix.git && cd flix
+```
+
+Beginners can [download the source code as a ZIP archive](https://github.com/okalachev/flix/archive/refs/heads/master.zip).
+
+## Building the firmware
+
+You can build and upload the firmware using either **Arduino IDE** (easier for beginners) or **command line**.
+
+### Arduino IDE (Windows, Linux, macOS)
+
+<img src="img/arduino-ide.png" width="400" alt="Flix firmware open in Arduino IDE">
+
+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. Open the `flix/flix.ino` sketch from downloaded firmware sources in Arduino IDE.
+6. 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.
+7. [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, install it like this:
+
+   ```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 [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 console and QGroundControl connection should work.
+
+## Before first flight
+
+### Choose the IMU model
+
+In case if using different IMU model than MPU9250, change `imu` variable declaration in the `imu.ino`:
+
+```cpp
+ICM20948 imu(SPI);  // For ICM-20948
+MPU6050 imu(Wire);  // For MPU-6050
+```
+
+### Setup the IMU orientation
+
+The IMU orientation is defined in `rotateIMU` function in the `imu.ino` file. Change it so it converts the IMU axes to the drone's axes correctly. **Drone axes are X forward, Y left, Z up**:
+
+<img src="img/drone-axes.svg" width="200">
+
+See various [IMU boards axes orientations table](https://github.com/okalachev/flixperiph/?tab=readme-ov-file#imu-axes-orientation) to help you set up the correct orientation.
+
+### Connect using QGroundControl
+
+QGroundControl is a ground control station software that can be used to monitor and control the drone.
+
+1. Install mobile or desktop version of [QGroundControl](https://docs.qgroundcontrol.com/master/en/qgc-user-guide/getting_started/download_and_install.html).
+2. Power up the drone.
+3. Connect your computer or smartphone to the appeared `flix` Wi-Fi network (password: `flixwifi`).
+4. Launch QGroundControl app. It should connect and begin showing the drone's telemetry automatically
+
+### Access console
+
+The console is a command line interface (CLI) that allows to interact with the drone, change parameters, and perform various actions. There are two ways of accessing the console: using **serial port** or using **QGroundControl (wirelessly)**.
+
+To access the console using serial port:
+
+1. Connect the ESP32 board to the computer using USB cable.
+2. Open Serial Monitor in Arduino IDE (or use `make monitor` in the command line).
+3. In Arduino IDE, make sure the baudrate is set to 115200.
+
+To access the console using QGroundControl:
+
+1. Connect to the drone using QGroundControl app.
+2. Go to the QGroundControl menu ⇒ *Vehicle Setup* ⇒ *Analyze Tools* ⇒ *MAVLink Console*.
+   <img src="img/cli.png" width="400">
+
+> [!TIP]
+> Use `help` command to see the list of available commands.
+
+### Calibrate accelerometer
+
+Before flight you need to calibrate the accelerometer:
+
+1. Access the console using QGroundControl (recommended) or Serial Monitor.
+2. Type `ca` command there and follow the instructions.
+
+### Check everything works
+
+1. 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).
+   * The `accel` and `gyro` fields should change as you move the drone.
+   * The `landed` field should be `1` when the drone is still on the ground and `0` when you lift it up.
+
+2. Check the attitude estimation: connect to the drone using QGroundControl, rotate the drone in different orientations and check if the attitude estimation shown in QGroundControl is correct. Attitude indicator in QGroundControl is shown below:
+
+   <img src="img/qgc-attitude.png" height="200">
+
+3. Perform motor tests in the console. Use the following commands **— remove the propellers before running the tests!**
+
+   * `mfr` — should rotate front right motor (counter-clockwise).
+   * `mfl` — should rotate front left motor (clockwise).
+   * `mrl` — should rotate rear left motor (counter-clockwise).
+   * `mrr` — should rotate rear right motor (clockwise).
+
+> [!WARNING]
+> Never run the motors when powering the drone from USB, always use the battery for that.
+
+## Setup remote control
+
+There are several ways to control the drone's flight: using **smartphone** (Wi-Fi), using **SBUS remote control**, or using **USB remote control** (Wi-Fi).
+
+### 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 `CTL_TILT_MAX` parameter when flying using the smartphone to make the controls less sensitive.
+
+### Control with remote control
+
+Before using remote SBUS-connected remote control, you need to calibrate it:
+
+1. Access the console using QGroundControl (recommended) or Serial Monitor.
+2. Type `cr` command 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 (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!
+
+## 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">
+
+> [!NOTE]
+> If something goes wrong, go to the [Troubleshooting](troubleshooting.md) article.
+
+### 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.
+
+#### RAW
+
+*RAW* mode disables all the stabilization, and the pilot inputs are mixed directly to the motors. The IMU sensor is not involved. 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. In order to do that, go to the QGroundControl menu ⇒ *Vehicle Setup* ⇒ *Parameters*.
+
+<img src="img/parameters.png" width="400">
+
+## Flight log
+
+After the flight, you can download the flight log for analysis wirelessly. Use the following for that:
+
+```bash
+make log
+```
+
+See more details about log analysis in the [log analysis](log.md) article.

docs/user.md

@@ -4,6 +4,111 @@ This page contains user-built drones based on the Flix project. Publish your pro
 
 ---
 
+Author: [goldarte](https://t.me/goldarte).<br>
+
+<img src="img/user/goldarte/1.jpg" height=150> <img src="img/user/goldarte/2.jpg" height=150>
+
+**Flight video:**
+
+<a href="https://drive.google.com/file/d/1nQtFjEcGGLx-l4xkL5ko9ZpOTVU-WDjL/view?usp=sharing"><img height=200 src="img/user/goldarte/video.jpg"></a>
+
+---
+
+## School 548 course
+
+Special quadcopter design and engineering course took place in october-november 2025 in School 548, Moscow. Course included UAV control theory, electronics, and practical drone assembly and setup using the Flix project.
+
+<img height=200 src="img/user/school548/1.jpg"> <img height=200 src="img/user/school548/2.jpg"> <img height=200 src="img/user/school548/3.jpg">
+
+### Selected works
+
+Author: [KiraFlux](https://t.me/@kiraflux_0XC0000005).<br>
+Description: **custom ESPNOW remote control** is implemented, firmware modified to support ESPNOW protocol.<br>
+Telegram posts: https://t.me/opensourcequadcopter/106, https://t.me/opensourcequadcopter/114.<br>
+Modified Flix firmware: https://github.com/KiraFlux/flix/tree/klyax.<br>
+Remote control project: https://github.com/KiraFlux/ESP32-DJC.<br>
+Drone design: https://github.com/KiraFlux/Klyax.<br>
+
+<img src="img/user/school548/kiraflux1.jpg" height=150> <img src="img/user/school548/kiraflux2.jpg" height=150>
+
+**Flight video**:
+
+<img height=200 src="img/user/school548/kiraflux-video.jpg"><a href="https://drive.google.com/file/d/1soHDAeHQWnm97Y4dg4nWevJuMiTdJJXW/view?usp=sharing"></a>
+
+Author: [tolyan4krut](https://t.me/tolyan4krut).<br>
+Description: the first drone based on ESP32-S3-CAM board **with a camera**, implementing Wi-Fi video streaming. Runs HTTP server and HTTP video stream.<br>
+Modified Flix firmware: https://github.com/CatRey/Flix-Camera-Streaming.<br>
+Telegram post: https://t.me/opensourcequadcopter/117.
+
+<img src="img/user/school548/tolyan4krut.jpg" height=150>
+
+**Flight video**:
+
+<a href="https://drive.google.com/file/d/1KuOBsujLsk7q8FoqKD8u7uoq4ptS5onp/view?usp=sharing"><img height=200 src="img/user/school548/tolyan4krut-video.jpg"></a>
+
+Author: [Vlad Tolshinov](https://t.me/Vlad_Tolshinov).<br>
+Description: custom frame with enlarged arm length, that provides very high level of stability, 65 mm props.
+
+<img src="img/user/school548/vlad_tolshinov1.jpg" height=150> <img src="img/user/school548/vlad_tolshinov2.jpg" height=150>
+
+---
+
+## 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 +122,14 @@ 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 +138,7 @@ 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 +151,7 @@ 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 +162,7 @@ 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 +171,7 @@ 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 +179,7 @@ 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 +188,4 @@ 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>

docs/version0.md

@@ -14,7 +14,7 @@ Flix version 0 (obsolete):
 |Motor|8520 3.7V brushed motor (**shaft 0.8mm!**)|<img src="img/motor.jpeg" width=100>|4|
 |Propeller|Hubsan 55 mm|<img src="img/prop.jpg" width=100>|4|
 |Motor ESC|2.7A 1S Dual Way Micro Brush ESC|<img src="img/esc.jpg" width=100>|4|
-|RC transmitter|KINGKONG TINY X8|<img src="img/tx.jpg" width=100>|1|
+|RC transmitter|KINGKONG TINY X8|<img src="img/kingkong.jpg" width=100>|1|
 |RC receiver|DF500 (SBUS)|<img src="img/rx.jpg" width=100>|1|
 |~~SBUS inverter~~*||<img src="img/inv.jpg" width=100>|~~1~~|
 |Battery|3.7 Li-Po 850 MaH 60C|||

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 RAW, 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 +33,17 @@ 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"
+"raw/stab/acro/auto - set mode\n"
 "rc - show RC data\n"
+"wifi - show Wi-Fi info\n"
 "mot - show motor output\n"
-"log - dump in-RAM log\n"
+"log [dump] - print log header [and data]\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 +60,30 @@ 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 +102,50 @@ 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 == "raw") {
+		mode = RAW;
+	} 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 == "wifi") {
+#if WIFI_ENABLED
+		printWiFiInfo();
+#endif
 	} 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();
+		printLogHeader();
+		if (arg0 == "dump") printLogData();
 	} else if (command == "cr") {
 		calibrateRC();
-	} else if (command == "cg") {
-		calibrateGyro();
 	} else if (command == "ca") {
 		calibrateAccel();
 	} else if (command == "mfr") {
@@ -136,12 +156,29 @@ 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 RAW = 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 +49,97 @@ 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() {
+	if (controlMode < 0.25) mode = STAB;
+	if (controlMode < 0.75) mode = STAB;
+	if (controlMode > 0.75) mode = STAB;
 
-	// 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 (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
+
+	if (abs(controlYaw) < 0.1) controlYaw = 0; // yaw dead zone
+
+	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
 	}
 
-	thrustTarget = controls[throttleChannel];
-
 	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 == RAW) { // direct torque control
+		attitudeTarget.invalidate(); // skip attitude control
+		ratesTarget.invalidate(); // skip rate control
+		torqueTarget = Vector(controlRoll, controlPitch, -controlYaw) * 0.1;
 	}
 }
 
 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;
 	}
 
@@ -171,10 +156,10 @@ void controlTorque() {
 
 const char* getModeName() {
 	switch (mode) {
-		case MANUAL: return "MANUAL";
+		case RAW: return "RAW";
 		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

@@ -7,22 +7,22 @@
 #include "quaternion.h"
 #include "util.h"
 
-#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");
+	Serial.begin(115200);
+	print("Initializing flix\n");
 	disableBrownOut();
 	setupParameters();
 	setupLED();
@@ -34,7 +34,7 @@ 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

@@ -4,13 +4,12 @@
 // In-RAM logging
 
 #include "vector.h"
+#include "util.h"
 
 #define LOG_RATE 100
 #define LOG_DURATION 10
-#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},
@@ -40,17 +39,15 @@ 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;
-	if (t - logTime < LOG_PERIOD) return;
-	logTime = t;
+	static Rate period(LOG_RATE);
+	if (!period) return;
 
 	prepareLogData();
 
@@ -64,12 +61,13 @@ void logData() {
 	}
 }
 
-void dumpLog() {
-	// Print header
+void printLogHeader() {
 	for (int i = 0; i < logColumns; i++) {
 		print("%s%s", logEntries[i].name, i < logColumns - 1 ? "," : "\n");
 	}
-	// Print data
+}
+
+void printLogData() {
 	for (int i = 0; i < LOG_SIZE; i++) {
 		if (logBuffer[i][0] == 0) continue; // skip empty records
 		for (int j = 0; j < logColumns; j++) {

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

@@ -6,17 +6,17 @@
 #if WIFI_ENABLED
 
 #include <MAVLink.h>
+#include "util.h"
 
 #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
+#define MAVLINK_RATE_SLOW 1
+#define MAVLINK_RATE_FAST 10
 
-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();
@@ -24,44 +24,46 @@ void processMavlink() {
 }
 
 void sendMavlink() {
-	static double lastSlow = 0;
-	static double lastFast = 0;
+	sendMavlinkPrint();
 
 	mavlink_message_t msg;
 	uint32_t time = t * 1000;
 
-	if (t - lastSlow >= PERIOD_SLOW) {
-		lastSlow = t;
+	static Rate slow(MAVLINK_RATE_SLOW), fast(MAVLINK_RATE_FAST);
 
-		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);
+	if (slow) {
+		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) {
-		lastFast = t;
-
+	if (fast && mavlinkConnected) {
 		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 +78,7 @@ 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 +91,19 @@ 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;
-
-		if (abs(controls[yawChannel]) < MAVLINK_CONTROL_YAW_DEAD_ZONE) controls[yawChannel] = 0;
+		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 (msg.msgid == MAVLINK_MSG_ID_PARAM_REQUEST_LIST) {
@@ -171,43 +171,109 @@ 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;
+	}
+
+	if (msg.msgid == MAVLINK_MSG_ID_LOG_REQUEST_DATA) {
+		mavlink_log_request_data_t m;
+		mavlink_msg_log_request_data_decode(&msg, &m);
+		if (m.target_system && m.target_system != SYSTEM_ID) return;
+
+		// Send all log records
+		for (int i = 0; i < sizeof(logBuffer) / sizeof(logBuffer[0]); i++) {
+			mavlink_message_t msg;
+			mavlink_msg_log_data_pack(SYSTEM_ID, MAV_COMP_ID_AUTOPILOT1, &msg, 0, i,
+				sizeof(logBuffer[0]), (uint8_t *)logBuffer[i]);
+			sendMessage(&msg);
+		}
+	}
+
 	// 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
@@ -38,9 +38,9 @@ void setupMotors() {
 
 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);
 }
 
@@ -55,7 +55,7 @@ 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

@@ -4,62 +4,60 @@
 // Parameters storage in flash memory
 
 #include <Preferences.h>
+#include "util.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 15 (Preferences key limit)
 	float *variable;
 	float value; // cache
 };
 
 Parameter parameters[] = {
 	// control
-	{"ROLLRATE_P", &rollRatePID.p},
-	{"ROLLRATE_I", &rollRatePID.i},
-	{"ROLLRATE_D", &rollRatePID.d},
-	{"ROLLRATE_I_LIM", &rollRatePID.windup},
-	{"PITCHRATE_P", &pitchRatePID.p},
-	{"PITCHRATE_I", &pitchRatePID.i},
-	{"PITCHRATE_D", &pitchRatePID.d},
-	{"PITCHRATE_I_LIM", &pitchRatePID.windup},
-	{"YAWRATE_P", &yawRatePID.p},
-	{"YAWRATE_I", &yawRatePID.i},
-	{"YAWRATE_D", &yawRatePID.d},
-	{"ROLL_P", &rollPID.p},
-	{"ROLL_I", &rollPID.i},
-	{"ROLL_D", &rollPID.d},
-	{"PITCH_P", &pitchPID.p},
-	{"PITCH_I", &pitchPID.i},
-	{"PITCH_D", &pitchPID.d},
-	{"YAW_P", &yawPID.p},
-	{"PITCHRATE_MAX", &maxRate.y},
-	{"ROLLRATE_MAX", &maxRate.x},
-	{"YAWRATE_MAX", &maxRate.z},
-	{"TILT_MAX", &tiltMax},
+	{"CTL_R_RATE_P", &rollRatePID.p},
+	{"CTL_R_RATE_I", &rollRatePID.i},
+	{"CTL_R_RATE_D", &rollRatePID.d},
+	{"CTL_R_RATE_WU", &rollRatePID.windup},
+	{"CTL_P_RATE_P", &pitchRatePID.p},
+	{"CTL_P_RATE_I", &pitchRatePID.i},
+	{"CTL_P_RATE_D", &pitchRatePID.d},
+	{"CTL_P_RATE_WU", &pitchRatePID.windup},
+	{"CTL_Y_RATE_P", &yawRatePID.p},
+	{"CTL_Y_RATE_I", &yawRatePID.i},
+	{"CTL_Y_RATE_D", &yawRatePID.d},
+	{"CTL_R_P", &rollPID.p},
+	{"CTL_R_I", &rollPID.i},
+	{"CTL_R_D", &rollPID.d},
+	{"CTL_P_P", &pitchPID.p},
+	{"CTL_P_I", &pitchPID.i},
+	{"CTL_P_D", &pitchPID.d},
+	{"CTL_Y_P", &yawPID.p},
+	{"CTL_P_RATE_MAX", &maxRate.y},
+	{"CTL_R_RATE_MAX", &maxRate.x},
+	{"CTL_Y_RATE_MAX", &maxRate.z},
+	{"CTL_TILT_MAX", &tiltMax},
 	// imu
-	{"ACC_BIAS_X", &accBias.x},
-	{"ACC_BIAS_Y", &accBias.y},
-	{"ACC_BIAS_Z", &accBias.z},
-	{"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},
+	{"IMU_ACC_BIAS_X", &accBias.x},
+	{"IMU_ACC_BIAS_Y", &accBias.y},
+	{"IMU_ACC_BIAS_Z", &accBias.z},
+	{"IMU_ACC_SCALE_X", &accScale.x},
+	{"IMU_ACC_SCALE_Y", &accScale.y},
+	{"IMU_ACC_SCALE_Z", &accScale.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 +66,11 @@ 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() {
@@ -120,10 +119,9 @@ bool setParameter(const char *name, const float value) {
 }
 
 void syncParameters() {
-	static double lastSync = 0;
-	if (t - lastSync < 1) return; // sync once per second
+	static Rate rate(1);
+	if (!rate) return; // sync once per second
 	if (motorsActive()) return; // don't use flash while flying, it may cause a delay
-	lastSync = t;
 
 	for (auto &parameter : parameters) {
 		if (parameter.value == *parameter.variable) continue;

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

@@ -10,13 +10,18 @@
 #include <soc/rtc_cntl_reg.h>
 
 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)
@@ -44,3 +49,37 @@ void splitString(String& str, String& token0, String& token1, String& token2) {
 	token1 = strtok(NULL, " "); // String(NULL) creates empty string
 	token2 = strtok(NULL, "");
 }
+
+// Rate limiter
+class Rate {
+public:
+	float rate;
+	float last = 0;
+	Rate(float rate) : rate(rate) {}
+
+	operator bool() {
+		if (t - last >= 1 / rate) {
+			last = t;
+			return true;
+		}
+		return false;
+	}
+};
+
+// 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;
+		} else 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();
 }
@@ -34,4 +35,15 @@ int receiveWiFi(uint8_t *buf, int len) {
 	return udp.read(buf, len);
 }
 
+void printWiFiInfo() {
+	print("MAC: %s\n", WiFi.softAPmacAddress().c_str());
+	print("SSID: %s\n", WiFi.softAPSSID().c_str());
+	print("Password: %s\n", WIFI_PASSWORD);
+	print("Clients: %d\n", WiFi.softAPgetStationNum());
+	print("Status: %d\n", WiFi.status());
+	print("IP: %s\n", WiFi.softAPIP().toString().c_str());
+	print("Remote IP: %s\n", udp.remoteIP().toString().c_str());
+	print("MAVLink connected: %d\n", mavlinkConnected);
+}
+
 #endif

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

@@ -1,15 +1,99 @@
-# Gazebo Simulation
+# Simulation
 
-<img src="../docs/img/simulator.png" width=500 alt="Flix simulator">
+The Flix drone simulator is based on Gazebo 11 and runs the firmware code in virtual physical environment.
 
-## Building and running
+Gazebo 11 works on **Ubuntu 20.04** and used to work on macOS. However, on the recent macOS versions it seems to be broken, so Ubuntu 20.04 is recommended.
 
-See [building and running instructions](../docs/build.md#simulation).
+<img src="../docs/img/simulator1.png" width=600 alt="Flix simulator running on macOS">
+
+## Installation
+
+1. Clone the Flix repository using it:
+
+   ```bash
+   git clone https://github.com/okalachev/flix.git && cd flix
+   ```
+
+2. Install Arduino CLI:
+
+   ```bash
+   curl -fsSL https://raw.githubusercontent.com/arduino/arduino-cli/master/install.sh | BINDIR=~/.local/bin sh
+   ```
+
+3. 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
+   ```
+
+4. Install SDL2 and other dependencies:
+
+   ```bash
+   sudo apt-get update && sudo apt-get install build-essential libsdl2-dev
+   ```
+
+5. 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
+   ```
+
+6. Run the simulation:
+
+   ```bash
+   make simulator
+   ```
+
+## Usage
+
+Just like the real drone, the simulator can be controlled using a USB remote control or a smartphone.
+
+### 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!
+
+> [!TIP]
+> Decrease `CTL_TILT_MAX` parameter when flying using the smartphone to make the controls less sensitive.
+
+### 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. Use the USB remote control to fly the drone!
+
+### Piloting
+
+To start the flight, arm the drone moving the throttle stick to the bottom right position:
+
+<img src="../docs/img/arming.svg" width="150">
+
+To disarm, move the throttle stick to the bottom left position:
+
+<img src="../docs/img/disarming.svg" width="150">
+
+See other piloting and usage details in general [usage article](../docs/usage.md).
 
 ## Code structure
 
-Flix simulator is based on [Gazebo Classic](https://classic.gazebosim.org) and consists of the following components:
+Flix simulator consists of the following components:
 
-* Physical model of the drone: [`models/flix/flix.sdf`](models/flix/flix.sdf).
+* Physical model of the drone in Gazebo format: [`models/flix/flix.sdf`](models/flix/flix.sdf).
 * Plugin for Gazebo: [`simulator.cpp`](simulator.cpp). The plugin is attached to the physical model. It receives stick positions from the controller, gets the data from the virtual sensors, and then passes this data to the Arduino code.
-* Arduino imitation: [`Arduino.h`](Arduino.h). This file contains partial implementation of the Arduino API, that is working within Gazebo plugin environment.
+* Arduino emulation: [`Arduino.h`](Arduino.h). This file contains partial implementation of the Arduino API, that is working within Gazebo plugin environment.

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();
@@ -28,33 +29,36 @@ 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 dumpLog();
+void calibrateRC();
+void calibrateRCChannel(float *channel, uint16_t zero[16], uint16_t max[16], const char *str);
+void printRCCalibration();
+void printLogHeader();
+void printLogData();
 void processMavlink();
 void sendMavlink();
 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 +71,7 @@ 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() {};
+void printWiFiInfo() {};
 Vector accBias, gyroBias, accScale(1, 1, 1);