Calibrate gyro continuously when landed and stationary

Don't have to wait until the request is timed out.

.editorconfig

@@ -4,8 +4,12 @@ root = true
 end_of_line = lf
 insert_final_newline = true
 
-[*.{ino,cpp,c,h,hpp,sdf,world}]
+[*.{ino,cpp,c,h,hpp,sdf,world,json}]
 charset = utf-8
 indent_style = tab
 tab_width = 4
 trim_trailing_whitespace = true
+
+[{*.yml,*.yaml,CMakeLists.txt}]
+indent_style = space
+indent_size = 2

.gitattributes

@@ -0,0 +1,2 @@
+# https://github.com/github-linguist/linguist/blob/master/docs/overrides.md
+*.h linguist-language=C++

.github/workflows/build.yml

@@ -7,39 +7,47 @@ on:
     branches: [ master ]
 
 jobs:
-  build:
+  build_linux:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - name: Install Arduino CLI
-      uses: arduino/setup-arduino-cli@v1.1.1
+      run: curl -fsSL https://raw.githubusercontent.com/arduino/arduino-cli/master/install.sh | BINDIR=/usr/local/bin sh
     - name: Build firmware
       run: make
+    - name: Check c_cpp_properties.json
+      run: tools/check_c_cpp_properties.py
 
   build_macos:
     runs-on: macos-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - name: Install Arduino CLI
       run: brew install arduino-cli
     - name: Build firmware
       run: make
+    - name: Check c_cpp_properties.json
+      run: tools/check_c_cpp_properties.py
 
   build_windows:
     runs-on: windows-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - name: Install Arduino CLI
       run: choco install arduino-cli
     - name: Install Make
       run: choco install make
     - name: Build firmware
       run: make
+    - name: Check c_cpp_properties.json
+      run: python3 tools/check_c_cpp_properties.py
 
   build_simulator:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - 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
     - name: Install SDL2
@@ -55,9 +63,18 @@ jobs:
 #  build_simulator_macos:
 #    runs-on: macos-latest
 #    steps:
-  #   - uses: actions/checkout@v3
+#    - name: Install Arduino CLI
+#      run: brew install arduino-cli
+#    - uses: actions/checkout@v4
+#    - name: Clean up python binaries # Workaround for https://github.com/actions/setup-python/issues/577
+#      run: |
+#        rm -f /usr/local/bin/2to3*
+#        rm -f /usr/local/bin/idle3*
+#        rm -f /usr/local/bin/pydoc3*
+#        rm -f /usr/local/bin/python3*
+#        rm -f /usr/local/bin/python3*-config
 #    - name: Install Gazebo
-  #     run: brew tap osrf/simulation && brew install gazebo11
+#      run: brew update && brew tap osrf/simulation && brew install gazebo11
 #    - name: Install SDL2
 #      run: brew install sdl2
 #    - name: Build simulator

.github/workflows/docs.yml

@@ -0,0 +1,51 @@
+name: Docs
+
+on:
+  push:
+    branches: [ '*' ]
+  pull_request:
+    branches: [ master ]
+
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+jobs:
+  markdownlint:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+    - name: Install markdownlint
+      run: npm install -g markdownlint-cli2
+    - name: Run markdownlint
+      run: markdownlint-cli2 "**/*.md"
+
+  build_book:
+    runs-on: ubuntu-latest
+    needs: markdownlint
+    steps:
+    - uses: actions/checkout@v4
+    - name: Install mdBook
+      run: cargo install mdbook --vers 0.4.43 --locked
+    - name: Build book
+      run: cd docs && mdbook build
+    - name: Upload artifact
+      uses: actions/upload-pages-artifact@v3
+      with:
+        path: docs/build
+
+  deploy:
+    if: ${{ github.event_name == 'push' && github.ref == 'refs/heads/master' }}
+    concurrency:
+      group: "pages"
+      cancel-in-progress: true
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    runs-on: ubuntu-latest
+    needs: build_book
+    steps:
+      - name: Deploy to GitHub Pages
+        id: deployment
+        uses: actions/deploy-pages@v4

.github/workflows/tools.yml

@@ -0,0 +1,33 @@
+name: Build tools
+
+on:
+  push:
+    branches: [ '*' ]
+  pull_request:
+    branches: [ master ]
+
+jobs:
+  csv_to_ulog:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+    - name: Build csv_to_ulog
+      run: cd tools/csv_to_ulog && mkdir build && cd build && cmake .. && make
+    - name: Test csv_to_ulog
+      run: |
+        cd tools/csv_to_ulog/build
+        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
+  python_tools:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+    - name: Install Python dependencies
+      run: pip install -r tools/requirements.txt
+    - name: Test csv_to_mcap tool
+      run: |
+        cd tools
+        echo -e "t,x,y,z\n0,1,2,3\n1,4,5,6" > log.csv
+        ./csv_to_mcap.py log.csv
+        test $(stat -c %s log.mcap) -eq 883

.gitignore

@@ -1,5 +1,12 @@
 *.hex
 *.elf
-gazebo/build/
+build/
 tools/log/
 .dependencies
+.vscode/*
+!.vscode/settings.json
+!.vscode/c_cpp_properties.json
+!.vscode/tasks.json
+!.vscode/launch.json
+!.vscode/extensions.json
+!.vscode/intellisense.h

.markdownlint.json

@@ -0,0 +1,67 @@
+{
+	"MD004": {
+		"style": "asterisk"
+	},
+	"MD010": false,
+	"MD013": false,
+	"MD024": false,
+	"MD033": false,
+	"MD034": false,
+	"MD044": {
+		"html_elements": false,
+		"code_blocks": false,
+		"names": [
+			"FlixPeriph",
+			"Wi-Fi",
+			"STM",
+			"Li-ion",
+			"GitHub",
+			"github.com",
+			"PPM",
+			"PWM",
+			"Futaba",
+			"S.Bus",
+			"C++",
+			"PID",
+			"Arduino IDE",
+			"Arduino",
+			"Arduino Nano",
+			"ESP32",
+			"IMU",
+			"MEMS",
+			"imu.ino",
+			"InvenSense",
+			"MPU-6050",
+			"MPU-9250",
+			"GY-91",
+			"ICM-20948",
+			"Linux",
+			"Windows",
+			"macOS",
+			"iOS",
+			"Android",
+			"Bluetooth",
+			"GPS",
+			"GPIO",
+			"USB",
+			"SPI",
+			"I²C",
+			"UART",
+			"GND",
+			"3V3",
+			"VCC",
+			"SCL",
+			"SDA",
+			"SAO",
+			"AD0",
+			"MOSI",
+			"MISO",
+			"NCS",
+			"MOSFET",
+			"ArduPilot",
+			"Betaflight",
+			"PX4"
+		]
+	},
+	"MD045": false
+}

.vscode/c_cpp_properties.json

@@ -0,0 +1,150 @@
+{
+	"configurations": [
+		{
+			"name": "Linux",
+			"includePath": [
+				"${workspaceFolder}/flix",
+				"${workspaceFolder}/gazebo",
+				"~/.arduino15/packages/esp32/hardware/esp32/3.0.7/cores/esp32",
+				"~/.arduino15/packages/esp32/hardware/esp32/3.0.7/libraries/**",
+				"~/.arduino15/packages/esp32/hardware/esp32/3.0.7/variants/d1_mini32",
+				"~/.arduino15/packages/esp32/tools/esp32-arduino-libs/idf-release_v5.1-632e0c2a/esp32/**",
+				"~/.arduino15/packages/esp32/tools/esp32-arduino-libs/idf-release_v5.1-632e0c2a/esp32/dio_qspi/include",
+				"~/Arduino/libraries/**",
+				"/usr/include/**"
+			],
+			"forcedInclude": [
+				"${workspaceFolder}/.vscode/intellisense.h",
+				"~/.arduino15/packages/esp32/hardware/esp32/3.0.7/cores/esp32/Arduino.h",
+				"~/.arduino15/packages/esp32/hardware/esp32/3.0.7/variants/d1_mini32/pins_arduino.h",
+				"${workspaceFolder}/flix/cli.ino",
+				"${workspaceFolder}/flix/control.ino",
+				"${workspaceFolder}/flix/estimate.ino",
+				"${workspaceFolder}/flix/flix.ino",
+				"${workspaceFolder}/flix/imu.ino",
+				"${workspaceFolder}/flix/led.ino",
+				"${workspaceFolder}/flix/log.ino",
+				"${workspaceFolder}/flix/mavlink.ino",
+				"${workspaceFolder}/flix/motors.ino",
+				"${workspaceFolder}/flix/rc.ino",
+				"${workspaceFolder}/flix/time.ino",
+				"${workspaceFolder}/flix/util.ino",
+				"${workspaceFolder}/flix/wifi.ino",
+				"${workspaceFolder}/flix/parameters.ino"
+			],
+			"compilerPath": "~/.arduino15/packages/esp32/tools/esp-x32/2302/bin/xtensa-esp32-elf-g++",
+			"cStandard": "c11",
+			"cppStandard": "c++17",
+			"defines": [
+				"F_CPU=240000000L",
+				"ARDUINO=10607",
+				"ARDUINO_D1_MINI32",
+				"ARDUINO_ARCH_ESP32",
+				"ARDUINO_BOARD=D1_MINI32",
+				"ARDUINO_VARIANT=d1_mini32",
+				"ARDUINO_PARTITION_default",
+				"ESP32",
+				"CORE_DEBUG_LEVEL=0",
+				"ARDUINO_USB_CDC_ON_BOOT="
+			]
+		},
+		{
+			"name": "Mac",
+			"includePath": [
+				"${workspaceFolder}/flix",
+				"${workspaceFolder}/gazebo",
+				"~/Library/Arduino15/packages/esp32/hardware/esp32/3.0.7/cores/esp32",
+				"~/Library/Arduino15/packages/esp32/hardware/esp32/3.0.7/libraries/**",
+				"~/Library/Arduino15/packages/esp32/hardware/esp32/3.0.7/variants/d1_mini32",
+				"~/Library/Arduino15/packages/esp32/tools/esp32-arduino-libs/idf-release_v5.1-632e0c2a/esp32/include/**",
+				"~/Library/Arduino15/packages/esp32/tools/esp32-arduino-libs/idf-release_v5.1-632e0c2a/esp32/dio_qspi/include",
+				"~/Documents/Arduino/libraries/**",
+				"/opt/homebrew/include/**"
+			],
+			"forcedInclude": [
+				"${workspaceFolder}/.vscode/intellisense.h",
+				"~/Library/Arduino15/packages/esp32/hardware/esp32/3.0.7/cores/esp32/Arduino.h",
+				"~/Library/Arduino15/packages/esp32/hardware/esp32/3.0.7/variants/d1_mini32/pins_arduino.h",
+				"${workspaceFolder}/flix/flix.ino",
+				"${workspaceFolder}/flix/cli.ino",
+				"${workspaceFolder}/flix/control.ino",
+				"${workspaceFolder}/flix/estimate.ino",
+				"${workspaceFolder}/flix/imu.ino",
+				"${workspaceFolder}/flix/led.ino",
+				"${workspaceFolder}/flix/log.ino",
+				"${workspaceFolder}/flix/mavlink.ino",
+				"${workspaceFolder}/flix/motors.ino",
+				"${workspaceFolder}/flix/rc.ino",
+				"${workspaceFolder}/flix/time.ino",
+				"${workspaceFolder}/flix/util.ino",
+				"${workspaceFolder}/flix/wifi.ino",
+				"${workspaceFolder}/flix/parameters.ino"
+			],
+			"compilerPath": "~/Library/Arduino15/packages/esp32/tools/esp-x32/2302/bin/xtensa-esp32-elf-g++",
+			"cStandard": "c11",
+			"cppStandard": "c++17",
+			"defines": [
+				"F_CPU=240000000L",
+				"ARDUINO=10607",
+				"ARDUINO_D1_MINI32",
+				"ARDUINO_ARCH_ESP32",
+				"ARDUINO_BOARD=D1_MINI32",
+				"ARDUINO_VARIANT=d1_mini32",
+				"ARDUINO_PARTITION_default",
+				"ARDUINO_FQBN=esp32:esp32:d1_mini32",
+				"ESP32",
+				"CORE_DEBUG_LEVEL=0",
+				"ARDUINO_USB_CDC_ON_BOOT="
+			]
+		},
+		{
+			"name": "Win32",
+			"includePath": [
+				"${workspaceFolder}/flix",
+				"${workspaceFolder}/gazebo",
+				"~/AppData/Local/Arduino15/packages/esp32/hardware/esp32/3.0.7/cores/esp32",
+				"~/AppData/Local/Arduino15/packages/esp32/hardware/esp32/3.0.7/libraries/**",
+				"~/AppData/Local/Arduino15/packages/esp32/hardware/esp32/3.0.7/variants/d1_mini32",
+				"~/AppData/Local/Arduino15/packages/esp32/tools/esp32-arduino-libs/idf-release_v5.1-632e0c2a/esp32/**",
+				"~/AppData/Local/Arduino15/packages/esp32/tools/esp32-arduino-libs/idf-release_v5.1-632e0c2a/esp32/dio_qspi/include",
+				"~/Documents/Arduino/libraries/**"
+			],
+			"forcedInclude": [
+				"${workspaceFolder}/.vscode/intellisense.h",
+				"~/AppData/Local/Arduino15/packages/esp32/hardware/esp32/3.0.7/cores/esp32/Arduino.h",
+				"~/AppData/Local/Arduino15/packages/esp32/hardware/esp32/3.0.7/variants/d1_mini32/pins_arduino.h",
+				"${workspaceFolder}/flix/cli.ino",
+				"${workspaceFolder}/flix/control.ino",
+				"${workspaceFolder}/flix/estimate.ino",
+				"${workspaceFolder}/flix/flix.ino",
+				"${workspaceFolder}/flix/imu.ino",
+				"${workspaceFolder}/flix/led.ino",
+				"${workspaceFolder}/flix/log.ino",
+				"${workspaceFolder}/flix/mavlink.ino",
+				"${workspaceFolder}/flix/motors.ino",
+				"${workspaceFolder}/flix/rc.ino",
+				"${workspaceFolder}/flix/time.ino",
+				"${workspaceFolder}/flix/util.ino",
+				"${workspaceFolder}/flix/wifi.ino",
+				"${workspaceFolder}/flix/parameters.ino"
+			],
+			"compilerPath": "~/AppData/Local/Arduino15/packages/esp32/tools/esp-x32/2302/bin/xtensa-esp32-elf-g++.exe",
+			"cStandard": "c11",
+			"cppStandard": "c++17",
+			"defines": [
+				"F_CPU=240000000L",
+				"ARDUINO=10607",
+				"ARDUINO_D1_MINI32",
+				"ARDUINO_ARCH_ESP32",
+				"ARDUINO_BOARD=D1_MINI32",
+				"ARDUINO_VARIANT=d1_mini32",
+				"ARDUINO_PARTITION_default",
+				"ARDUINO_FQBN=esp32:esp32:d1_mini32",
+				"ESP32",
+				"CORE_DEBUG_LEVEL=0",
+				"ARDUINO_USB_CDC_ON_BOOT="
+			]
+		}
+	],
+	"version": 4
+}

.vscode/extensions.json

@@ -0,0 +1,10 @@
+{
+	// 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"
+	],
+	"unwantedRecommendations": []
+}

.vscode/intellisense.h

@@ -0,0 +1,5 @@
+#ifdef __INTELLISENSE__
+	#pragma diag_suppress 144, 513
+	// diag 144: a value of type "enum <unnamed>" cannot be used to initialize an entity of type "enum <unnamed>"C/C++
+	// diag 513: a value of type "enum <unnamed>" cannot be assigned to an entity of type "enum <unnamed>"C/C++
+#endif

.vscode/launch.json

@@ -0,0 +1,25 @@
+{
+	"version": "0.2.0",
+	"configurations": [
+		{
+			"name": "Debug simulation",
+			"type": "cppdbg",
+			"request": "launch",
+			"program": "/usr/bin/gzserver",
+			"osx": {
+				"program": "/opt/homebrew/bin/gzserver",
+				"MIMode": "lldb",
+			},
+			"args": ["--verbose", "${workspaceFolder}/gazebo/flix.world"],
+			"stopAtEntry": false,
+			"cwd": "${fileDirname}",
+			"environment": [
+				{"name": "GAZEBO_MODEL_PATH", "value": "${workspaceFolder}/gazebo/models"},
+				{"name": "GAZEBO_PLUGIN_PATH", "value": "${workspaceFolder}/gazebo/build"}
+			],
+			"MIMode": "gdb",
+			"preLaunchTask": "Build simulator",
+			"externalConsole": true,
+		},
+	]
+}

.vscode/settings.json

@@ -0,0 +1,13 @@
+{
+	"C_Cpp.intelliSenseEngineFallback": "enabled",
+	"files.associations": {
+		"*.sdf": "xml",
+		"*.ino": "cpp",
+		"*.h": "cpp"
+	},
+	"C_Cpp.vcFormat.newLine.beforeOpenBrace.function": "newLine",
+	"C_Cpp.vcFormat.newLine.beforeOpenBrace.block": "sameLine",
+	"C_Cpp.vcFormat.newLine.beforeOpenBrace.lambda": "sameLine",
+	"C_Cpp.vcFormat.newLine.beforeOpenBrace.namespace": "sameLine",
+	"C_Cpp.vcFormat.newLine.beforeOpenBrace.type": "sameLine"
+}

.vscode/tasks.json

@@ -0,0 +1,31 @@
+{
+	"tasks": [
+		{
+			"label": "Build firmware",
+			"type": "shell",
+			"command": "make",
+			"problemMatcher": [ "$gcc" ],
+			"presentation": { "clear": true, "showReuseMessage": false },
+		},
+		{
+			"label": "Upload firmware",
+			"type": "shell",
+			"command": "make upload",
+			"problemMatcher": [ "$gcc" ],
+			"presentation": { "clear": true, "showReuseMessage": false }
+		},
+		{
+			"label": "Build simulator",
+			"type": "shell",
+			"command": "make build_simulator",
+			"problemMatcher": [ "$gcc" ],
+			"presentation": { "clear": true, "showReuseMessage": false }
+		},
+		{
+			"label": "Clean",
+			"type": "shell",
+			"command": "make clean",
+		}
+	],
+	"version": "2.0.0"
+}

Makefile

@@ -1,5 +1,5 @@
 BOARD = esp32:esp32:d1_mini32
-PORT := $(wildcard /dev/serial/by-id/usb-Silicon_Labs_CP2104_USB_to_UART_Bridge_Controller_* /dev/serial/by-id/usb-1a86_USB_Single_Serial_* /dev/cu.usbserial-*)
+PORT := $(wildcard /dev/serial/by-id/usb-Silicon_Labs_CP21* /dev/serial/by-id/usb-1a86_USB_Single_Serial_* /dev/cu.usbserial-*)
 PORT := $(strip $(PORT))
 
 build: .dependencies
@@ -13,16 +13,17 @@ monitor:
 
 dependencies .dependencies:
 	arduino-cli core update-index --config-file arduino-cli.yaml
-	arduino-cli core install esp32:esp32@2.0.11 --config-file arduino-cli.yaml
-	arduino-cli lib install "Bolder Flight Systems SBUS"@1.0.1
-	arduino-cli lib install --git-url https://github.com/okalachev/MPU9250.git --config-file arduino-cli.yaml
+	arduino-cli core install esp32:esp32@3.0.7 --config-file arduino-cli.yaml
+	arduino-cli lib update-index
+	arduino-cli lib install "FlixPeriph"
+	arduino-cli lib install "MAVLink"@2.0.12
 	touch .dependencies
 
 gazebo/build cmake: gazebo/CMakeLists.txt
 	mkdir -p gazebo/build
 	cd gazebo/build && cmake ..
 
-build_simulator: gazebo/build
+build_simulator: .dependencies gazebo/build
 	make -C gazebo/build
 
 simulator: build_simulator
@@ -36,9 +37,6 @@ log:
 plot:
 	plotjuggler -d $(shell ls -t tools/log/*.csv | head -n1)
 
-docs:
-	for FILE in docs/*.d2; do d2 $$FILE; done
-
 clean:
 	rm -rf gazebo/build flix/build flix/cache .dependencies
 

README.md

@@ -1,58 +1,156 @@
-# flix
+# Flix
 
-**flix** (*flight + X*) — making an open source ESP32-based quadcopter from scratch.
+**Flix** (*flight + X*) — making an open source ESP32-based quadcopter from scratch.
 
-<img src="docs/img/flix.jpg" width=500>
+<table>
+  <tr>
+    <td align=center><strong>Version 1</strong> (3D-printed frame)</td>
+    <td align=center><strong>Version 0</strong></td>
+  </tr>
+  <tr>
+    <td><img src="docs/img/flix1.jpg" width=500 alt="Flix quadcopter"></td>
+    <td><img src="docs/img/flix.jpg" width=500 alt="Flix quadcopter"></td>
+  </tr>
+</table>
 
 ## Features
 
-* Simple and clear Arduino based source code.
+* Simple and clean Arduino based source code.
 * Acro and Stabilized flight using remote control.
 * Precise simulation using Gazebo.
-* In-RAM logging.
+* [In-RAM logging](docs/log.md).
 * Command line interface through USB port.
 * Wi-Fi support.
-* ESCs with reverse mode support.
-* *Textbook and videos for students on writing a flight controller\*.*
-* *MAVLink support\*.*
-* *Completely 3D-printed frame*.*
-* *Position control and autonomous flights using external camera\**.
+* 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).
 
-*\* — planned.*
+*¹ — planned.*
 
 ## It actually flies
 
+See detailed demo video (for version 0): https://youtu.be/8GzzIQ3C6DQ.
+
 <a href="https://youtu.be/8GzzIQ3C6DQ"><img width=500 src="https://i3.ytimg.com/vi/8GzzIQ3C6DQ/maxresdefault.jpg"></a>
 
-See YouTube demo video: https://youtu.be/8GzzIQ3C6DQ.
+Version 1 test flight: https://t.me/opensourcequadcopter/42.
+
+<a href="https://t.me/opensourcequadcopter/42"><img width=500 src="docs/img/flight-video.jpg"></a>
 
 ## Simulation
 
-Simulation in Gazebo using a plugin that runs original Arduino code is implemented:
+The simulator is implemented using Gazebo and runs the original Arduino code:
 
-<img src="docs/img/simulator.png" width=500>
+<img src="docs/img/simulator.png" width=500 alt="Flix simulator">
 
-## Schematics
+See [instructions on running the simulation](docs/build.md).
 
-<img src="docs/img/schematics.svg" width=800>
+## Components (version 1)
+
+|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!**)|<img src="docs/img/motor.jpeg" width=100>|4|
+|Propeller|Hubsan 55 mm|<img src="docs/img/prop.jpg" width=100>|4|
+|MOSFET (transistor)|100N03A or [analog](https://t.me/opensourcequadcopter/33)|<img src="docs/img/100n03a.jpg" width=100>|4|
+|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|
+|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.stl`](docs/assets/flix-frame.stl) [`flix-frame.step`](docs/assets/flix-frame.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>|1|
+|*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|
+|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.*
+
+Tools required for assembly:
+
+* 3D printer.
+* Soldering iron.
+* Solder wire (with flux).
+* 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)).
+
+## Schematics (version 1)
+
+### Simplified connection diagram
+
+<img src="docs/img/schematics1.svg" width=800 alt="Flix version 1 schematics">
+
+Motor connection scheme:
+
+<img src="docs/img/mosfet-connection.png" height=400 alt="MOSFET connection scheme">
+
+Complete diagram is Work-in-Progress.
+
+### Notes
+
+* Power ESP32 Mini with Li-Po battery using VCC (+) and GND (-) pins.
+* Connect the IMU board to the ESP32 Mini using VSPI, power it using 3.3V and GND pins:
+
+  |IMU pin|ESP32 pin|
+  |-|-|
+  |GND|GND|
+  |3.3V|3.3V|
+  |SCL *(SCK)*|SVP (GPIO18)|
+  |SDA *(MOSI)*|GPIO23|
+  |SAO *(MISO)*|GPIO19|
+  |NCS|GPIO5|
+
+* 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|
+  |Motor 1|Rear right|Clockwise|Blue & Red|GPIO13|
+  |Motor 2|Front right|Counter-clockwise|Black & White|GPIO14|
+  |Motor 3|Front left|Clockwise|Blue & Red|GPIO15|
+
+  Counter-clockwise motors have black and white wires and clockwise motors have blue and red wires.
+
+* Optionally connect the RC receiver to the ESP32's UART2:
+
+  |Receiver pin|ESP32 pin|
+  |-|-|
+  |GND|GND|
+  |VIN|VC (or 3.3V depending on the receiver)|
+  |Signal|GPIO4⁶|
+
+*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.*
+
+### IMU placement
+
+Default IMU orientation in the code is **LFD** (Left-Forward-Down):
+
+<img src="docs/img/gy91-lfd.svg" width=400 alt="GY-91 axes">
+
+In case of using other IMU orientation, modify the `rotateIMU` function in the `imu.ino` file.
+
+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
 
-### Components
+See the information on the obsolete version 0 in the [corresponding article](docs/version0.md).
 
-|Component|Type|Image|Quantity|
-|-|-|-|-|
-|ESP32 Mini|Microcontroller board|<img src="docs/img/esp32.jpg" width=100>|1|
-|GY-91|IMU+LDO+barometer board|<img src="docs/img/gy-91.jpg" width=100>|1|
-|K100|Quadcopter frame|<img src="docs/img/frame.jpg" width=100>|1|
-|8520 3.7V brushed motor|Motor|<img src="docs/img/motor.jpeg" width=100>|4|
-|Hubsan 55 mm| Propeller|<img src="docs/img/prop.jpg" width=100>|4|
-|2.7A 1S Dual Way Micro Brush ESC|Motor ESC|<img src="docs/img/esc.jpg" width=100>|4|
-|KINGKONG TINY X8|RC transmitter|<img src="docs/img/tx.jpg" width=100>|1|
-|DF500 (SBUS)|RC receiver|<img src="docs/img/rx.jpg" width=100>|1|
-||SBUS inverter|<img src="docs/img/inv.jpg" width=100>|1|
-|3.7 Li-Po 850 MaH 60C|Battery|||
-||Battery charger|<img src="docs/img/charger.jpg" width=100>|1|
-||Wires, connectors, tape, ...||
-||3D-printed frame parts||
+## 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/.

arduino-cli.yaml

@@ -1,5 +1,3 @@
 board_manager:
   additional_urls:
     - https://raw.githubusercontent.com/espressif/arduino-esp32/gh-pages/package_esp32_index.json
-library:
-  enable_unsafe_install: true

docs/Makefile

@@ -0,0 +1,10 @@
+build:
+	mdbook build
+
+serve:
+	mdbook serve
+
+clean:
+	mdbook clean
+
+.PHONY: build serve clean

docs/alerts.py

@@ -0,0 +1,31 @@
+# https://rust-lang.github.io/mdBook/format/configuration/preprocessors.html
+# https://rust-lang.github.io/mdBook/for_developers/preprocessors.html
+
+import json
+import sys
+import re
+
+
+def transform_markdown_to_html(markdown_text):
+    def replace_blockquote(match):
+        tag = match.group(1).lower()
+        content = match.group(2).strip().replace('\n> ', ' ')
+        return f'<div class="alert alert-{tag}">{content}</div>\n'
+
+    pattern = re.compile(r'> \[!(NOTE|TIP|IMPORTANT|WARNING|CAUTION)\]\n>(.*?)\n?(?=(\n[^>]|\Z))', re.DOTALL)
+    transformed_text = pattern.sub(replace_blockquote, markdown_text)
+    return transformed_text
+
+
+if __name__ == '__main__':
+    if len(sys.argv) > 1:
+        if sys.argv[1] == 'supports':
+            sys.exit(0)
+
+    context, book = json.load(sys.stdin)
+
+    for section in book['sections']:
+        if 'Chapter' in section:
+            section['Chapter']['content'] = transform_markdown_to_html(section['Chapter']['content'])
+
+    print(json.dumps(book))

docs/assets/washer-m3.step

@@ -0,0 +1,200 @@
+ISO-10303-21;
+HEADER;
+
+FILE_DESCRIPTION(
+/* description */ (''),
+/* implementation_level */ '2;1');
+
+FILE_NAME(
+/* name */ 'washer-m3.step',
+/* time_stamp */ '2024-10-29T13:59:42+03:00',
+/* author */ (''),
+/* organization */ (''),
+/* preprocessor_version */ '',
+/* originating_system */ '',
+
+/* authorisation */ '');
+
+FILE_SCHEMA (('AUTOMOTIVE_DESIGN { 1 0 10303 214 3 1 1 }'));
+ENDSEC;
+
+DATA;
+#10=MECHANICAL_DESIGN_GEOMETRIC_PRESENTATION_REPRESENTATION('',(#13),#125);
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+#14=MANIFOLD_SOLID_BREP('Body1',#65);
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+POSITIVE_RATIO_MEASURE(7850.),#69);
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+#72=PROPERTY_DEFINITION_REPRESENTATION(#77,#74);
+#73=REPRESENTATION('material name',(#75),#124);
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+#122=UNCERTAINTY_MEASURE_WITH_UNIT(LENGTH_MEASURE(0.01),#126,
+'DISTANCE_ACCURACY_VALUE',
+'Maximum model space distance between geometric entities at asserted c
+onnectivities');
+#123=UNCERTAINTY_MEASURE_WITH_UNIT(LENGTH_MEASURE(0.01),#126,
+'DISTANCE_ACCURACY_VALUE',
+'Maximum model space distance between geometric entities at asserted c
+onnectivities');
+#124=(
+GEOMETRIC_REPRESENTATION_CONTEXT(3)
+GLOBAL_UNCERTAINTY_ASSIGNED_CONTEXT((#122))
+GLOBAL_UNIT_ASSIGNED_CONTEXT((#126,#128,#129))
+REPRESENTATION_CONTEXT('','3D')
+);
+#125=(
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+REPRESENTATION_CONTEXT('','3D')
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+#132=SHAPE_REPRESENTATION('',(#78),#124);
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+#136=PRODUCT_RELATED_PRODUCT_CATEGORY('washer-m3','washer-m3',(#140));
+#137=APPLICATION_PROTOCOL_DEFINITION('international standard',
+'automotive_design',2009,#138);
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+'Core Data for Automotive Mechanical Design Process');
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+#141=PRESENTATION_STYLE_ASSIGNMENT((#142));
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+#143=SURFACE_SIDE_STYLE('',(#144));
+#144=SURFACE_STYLE_FILL_AREA(#145);
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+#147=COLOUR_RGB('Steel - Satin',0.627450980392157,0.627450980392157,0.627450980392157);
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+END-ISO-10303-21;

docs/book.css

@@ -0,0 +1,110 @@
+.sidebar-resize-handle { display: none !important; }
+
+footer {
+	contain: content;
+	border-top: 3px solid #f4f4f4;
+}
+
+footer a.telegram, footer a.github {
+	display: block;
+	margin-bottom: 10px;
+	margin-top: 10px;
+	display: flex;
+	align-items: center;
+	text-decoration: none;
+}
+
+.content .github, .content .telegram {
+	display: flex;
+	align-items: center;
+	text-align: center;
+	justify-content: center;
+}
+
+.telegram::before, .github::before {
+	font-family: FontAwesome;
+	margin-right: 0.3em;
+	font-size: 1.6em;
+	color: black;
+}
+
+.github::before {
+	content: "\f09b";
+}
+
+.telegram::before {
+	font-size: 1.4em;
+	color: #0084c5;
+	content: "\f2c6";
+}
+
+.content hr {
+	border: none;
+	border-top: 2px solid #c9c9c9;
+	margin: 2em 0;
+}
+
+.content img {
+	display: block;
+	margin: 0 auto;
+}
+
+.content img.border {
+	border: 1px solid #c9c9c9;
+}
+
+.firmware {
+	position: relative;
+	margin: 20px 0;
+	padding: 20px 20px;
+	padding-left: 60px;
+	color: var(--fg);
+	background-color: var(--quote-bg);
+	border-block-start: .1em solid var(--quote-border);
+	border-block-end: .1em solid var(--quote-border);
+}
+
+.firmware::before {
+	font-family: FontAwesome;
+	font-size: 1.5em;
+	content: "\f15b";
+	position: absolute;
+	width: 20px;
+	text-align: center;
+	left: 20px;
+}
+
+.alert {
+	margin-top: 20px;
+	margin-bottom: 20px;
+	position: relative;
+	border-left: 2px solid #0a69da;
+	padding: 20px;
+	padding-left: 60px;
+}
+
+.alert::before {
+	font-family: FontAwesome;
+	font-size: 1.5em;
+	color: #0a69da;
+	content: "\f05a";
+	position: absolute;
+	width: 20px;
+	text-align: center;
+	left: 20px;
+}
+
+.alert-tip { border-left-color: #1b7f37; }
+.alert-tip::before { color: #1b7f37; content: '\f0eb'; }
+
+.alert-caution { border-left-color: #cf212e; }
+.alert-caution::before { color: #cf212e; content: '\f071'; }
+
+.alert-important { border-left-color: #8250df; }
+.alert-important::before { color: #8250df; content: '\f06a'; }
+
+.alert-warning { border-left-color: #f0ad4e; }
+.alert-warning::before { color: #f0ad4e; content: '\f071'; }
+
+.alert-code { border-left-color: #333; }
+.alert-code::before { color: #333; content: '\f121'; }

docs/book.toml

@@ -0,0 +1,22 @@
+[book]
+authors = ["Oleg Kalachev"]
+language = "ru"
+multilingual = false
+src = "book"
+title = "Полетный контроллер с нуля"
+description = "Учебник по разработке полетного контроллера квадрокоптера"
+
+[build]
+build-dir = "build"
+
+[output.html]
+additional-css = ["book.css", "zoom.css"]
+additional-js = ["zoom.js", "js.js"]
+edit-url-template = "https://github.com/okalachev/flix/blob/master/docs/{path}?plain=1"
+mathjax-support = true
+
+[output.html.code.hidelines]
+cpp = "//~"
+
+[preprocessor.alerts]
+command = "python3 alerts.py"

docs/book/README.md

@@ -0,0 +1,10 @@
+# Flix
+
+> [!IMPORTANT]
+> Flix — это проект по созданию открытого квадрокоптера на базе ESP32 с нуля и учебника по разработке полетных контроллеров.
+
+<img src="img/flix1.jpg" class="border" width=500 alt="Flix quadcopter">
+
+<p class="github">GitHub:&nbsp;<a href="https://github.com/okalachev/flix">github.com/okalachev/flix</a>.</p>
+
+<p class="telegram">Telegram-канал:&nbsp;<a href="https://t.me/opensourcequadcopter">@opensourcequadcopter</a>.</p>

docs/book/SUMMARY.md

@@ -0,0 +1,22 @@
+<!-- markdownlint-disable MD041 -->
+<!-- markdownlint-disable MD042 -->
+
+[Главная](./README.md)
+
+* [Архитектура прошивки](firmware.md)
+
+# Учебник
+
+* [Основы]()
+* [Светодиод]()
+* [Моторы]()
+* [Радиоуправление]()
+* [Гироскоп](gyro.md)
+* [Акселерометр]()s
+* [Оценка состояния]()
+* [PID-регулятор]()
+* [Режим ACRO]()
+* [Режим STAB]()
+* [Wi-Fi]()
+* [MAVLink]()
+* [Симуляция]()

docs/book/firmware.md

@@ -0,0 +1,32 @@
+# Архитектура прошивки
+
+<img src="img/dataflow.svg" width=800 alt="Firmware dataflow diagram">
+
+Главный цикл 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*.
+* `gyro` *(Vector)* — данные с гироскопа, *рад/с*.
+* `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).
+
+## Исходные файлы
+
+Исходные файлы прошивки находятся в директории `flix`. Ключевые 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.
+
+Вспомогательные файлы включают:
+
+* [`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.

docs/book/gyro.md

@@ -0,0 +1,262 @@
+# Гироскоп
+
+<div class="firmware">
+	<strong>Файл прошивки Flix:</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>
+
+Поддержание стабильного полета квадрокоптера невозможно без датчиков обратной связи. Важнейший из них — это **MEMS-гироскоп**. MEMS-гироскоп это микроэлектромеханический аналог классического механического гироскопа.
+
+Механический гироскоп состоит из вращающегося диска, который сохраняет свою ориентацию в пространстве. Благодаря этому эффекту возможно определить ориентацию объекта в пространстве.
+
+В MEMS-гироскопе нет вращающихся частей, и он помещается в крошечную микросхему. Он может измерять только текущую угловую скорость вращения объекта вокруг трех осей: X, Y и Z.
+
+|Механический гироскоп|MEMS-гироскоп|
+|-|-|
+|<img src="img/gyroscope.jpg" width="300" alt="Механический гироскоп">|<img src="img/mpu9250.jpg" width="100" alt="MEMS-гироскоп MPU-9250">|
+
+MEMS-гироскоп обычно интегрирован в инерциальный модуль (IMU), в котором также находятся акселерометр и магнитометр. Модуль IMU часто называют 9-осевым датчиком, потому что он измеряет:
+
+* Угловую скорость вращения по трем осям (гироскоп).
+* Ускорение по трем осям (акселерометр).
+* Магнитное поле по трем осям (магнитометр).
+
+Flix поддерживает следующие модели IMU:
+
+* InvenSense MPU-9250.
+* InvenSense MPU-6500.
+* InvenSense ICM-20948.
+
+> [!NOTE]
+> MEMS-гироскоп измеряет угловую скорость вращения объекта.
+
+## Интерфейс подключения
+
+Большинство модулей IMU подключаются к микроконтроллеру через интерфейсы I²C и SPI. Оба этих интерфейса являются *шинами данных*, то есть позволяют подключить к одному микроконтроллеру несколько устройств.
+
+**Интерфейс I²C** использует два провода для передачи данных и тактового сигнала. Выбор устройства для коммуникации происходит при помощи передачи адреса устройства на шину. Разные устройства имеют разные адреса, и микроконтроллер может последовательно общаться с несколькими устройствами.
+
+**Интерфейс SPI** использует два провода для передачи данных, еще один для тактового сигнала и еще один для выбора устройства. При этом для каждого устройства на шине выделяется отдельный GPIO-пин для выбора. В разных реализациях этот пин называется CS/NCS (Chip Select) или SS (Slave Select). Когда CS-пин устройства активен (напряжение на нем низкое), устройство выбрано для общения.
+
+В полетных контроллерах IMU обычно подключают через SPI, потому что он обеспечивает значительно бо́льшую скорость передачи данных и меньшую задержку. Подключение IMU через интерфейс I²C (например, в случае нехватки пинов микроконтроллера) возможно, но не рекомендуется.
+
+Подключение IMU к микроконтроллеру ESP32 через интерфейс SPI выглядит так:
+
+|Пин платы IMU|Пин ESP32|
+|-|-|
+|VCC/3V3|3V3|
+|GND|GND|
+|SCL|IO18|
+|SDA *(MOSI)*|IO23|
+|SAO/AD0 *(MISO)*|IO19|
+|NCS|IO5|
+
+Кроме того, многие IMU могут «будить» микроконтроллер при наличии новых данных. Для этого используется пин INT, который подключается к любому GPIO-пину микроконтроллера. При такой конфигурации можно использовать прерывания для обработки новых данных с IMU, вместо периодического опроса датчика. Это позволяет снизить нагрузку на микроконтроллер в сложных алгоритмах управления.
+
+> [!WARNING]
+> На некоторых платах IMU, например, на ICM-20948, отсутствует стабилизатор напряжения, поэтому их нельзя подключать к пину VIN ESP32, который подает напряжение 5 В. Допустимо питание только от пина 3V3.
+
+## Работа с гироскопом
+
+Для взаимодействия с IMU, включая работу с гироскопом, в Flix используется библиотека *FlixPeriph*. Библиотека устанавливается через менеджер библиотек Arduino IDE:
+
+<img src="img/flixperiph.png" width="300">
+
+Чтобы работать с IMU, используется класс, соответствующий модели IMU: `MPU9250`, `MPU6500` или `ICM20948`. Классы для работы с разными IMU имеют единообразный интерфейс для основных операций, поэтому возможно легко переключаться между разными моделями IMU. Датчик MPU-6500 практически полностью совместим с MPU-9250, поэтому фактически класс `MPU9250` поддерживает обе модели.
+
+## Ориентация осей гироскопа
+
+Данные с гироскопа представляют собой угловую скорость вокруг трех осей: X, Y и Z. Ориентацию этих осей у IMU InvenSense можно легко определить по небольшой точке в углу чипа. Оси координат и направление вращения для измерений гироскопа обозначены на диаграмме:
+
+<img src="img/imu-axes.svg" width="300" alt="Оси координат IMU">
+
+Расположение осей координат в популярных платах IMU:
+
+|GY-91|MPU-92/65|ICM-20948|
+|-|-|-|
+|<img src="https://github.com/okalachev/flixperiph/raw/refs/heads/master/img/gy91-axes.svg" width="200" alt="Оси координат платы GY-91">|<img src="https://github.com/okalachev/flixperiph/raw/refs/heads/master/img/mpu9265-axes.svg" width="200" alt="Оси координат платы MPU-9265">|<img src="https://github.com/okalachev/flixperiph/raw/refs/heads/master/img/icm20948-axes.svg" width="200" alt="Оси координат платы ICM-20948">|
+
+Магнитометр IMU InvenSense обычно является отдельным устройством, интегрированным в чип, поэтому его оси координат могут отличаться. Библиотека FlixPeriph скрывает это различие и приводит данные с магнитометра к системе координат гироскопа и акселерометра.
+
+## Чтение данных
+
+Интерфейс библиотеки FlixPeriph соответствует стилю, принятому в Arduino. Для начала работы с IMU необходимо создать объект соответствующего класса и вызвать метод `begin()`. В конструктор класса передается интерфейс, по которому подключен IMU (SPI или I²C):
+
+```cpp
+#include <FlixPeriph.h>
+#include <SPI.h>
+
+MPU9250 IMU(SPI);
+
+void setup() {
+	Serial.begin(115200);
+	bool success = IMU.begin();
+	if (!success) {
+		Serial.println("Failed to initialize IMU");
+	}
+}
+```
+
+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.
+
+Программа для чтения данных с гироскопа и вывода их в консоль для построения графиков в Serial Plotter выглядит так:
+
+```cpp
+#include <FlixPeriph.h>
+#include <SPI.h>
+
+MPU9250 IMU(SPI);
+
+void setup() {
+	Serial.begin(115200);
+	bool success = IMU.begin();
+	if (!success) {
+		Serial.println("Failed to initialize IMU");
+	}
+}
+
+void loop() {
+	IMU.waitForData();
+
+	float gx, gy, gz;
+	IMU.getGyro(gx, gy, gz);
+
+	Serial.printf("gx:%f gy:%f gz:%f\n", gx, gy, gz);
+	delay(50); // замедление вывода
+}
+```
+
+После запуска программы в Serial Plotter можно увидеть графики угловых скоростей. Например, при вращениях IMU вокруг вертикальной оси Z графики будут выглядеть так:
+
+<img src="img/gyro-plotter.png">
+
+## Конфигурация гироскопа
+
+В коде Flix настройка IMU происходит в функции `configureIMU`. В этой функции настраиваются три основных параметра гироскопа: диапазон измерений, частота сэмплов и частота LPF-фильтра.
+
+### Частота сэмплов
+
+Большинство IMU могут обновлять данные с разной частотой. В полетных контроллерах обычно используется частота обновления от 500 Гц до 8 кГц. Чем выше частота сэмплов, тем выше точность управления полетом, но и больше нагрузка на микроконтроллер. В Flix используется частота сэмплов 1 кГц.
+
+Частота сэмплов устанавливается методом `setSampleRate()`. В Flix используется частота 1 кГц:
+
+```cpp
+IMU.setRate(IMU.RATE_1KHZ_APPROX);
+```
+
+Поскольку не все поддерживаемые IMU могут работать строго на частоте 1 кГц, в библиотеке FlixPeriph существует возможность приближенной настройки частоты сэмплов. Например, у IMU ICM-20948 при такой настройке реальная частота сэмплирования будет равна 1125 Гц.
+
+Другие доступные для установки в библиотеке FlixPeriph частоты сэмплирования:
+
+* `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_8KHZ_APPROX` — значение, близкое к 8 кГц.
+* `RATE_MAX` — максимальная частота сэмплов для конкретного IMU.
+
+#### Диапазон измерений
+
+Большинство MEMS-гироскопов поддерживают несколько диапазонов измерений угловой скорости. Главное преимущество выбора меньшего диапазона — бо́льшая чувствительность. В полетных контроллерах обычно выбирается максимальный диапазон измерений от –2000 до 2000 градусов в секунду, чтобы обеспечить возможность динамичных маневров.
+
+В библиотеке FlixPeriph диапазон измерений гироскопа устанавливается методом `setGyroRange()`:
+
+```cpp
+IMU.setGyroRange(IMU.GYRO_RANGE_2000DPS);
+```
+
+### LPF-фильтр
+
+IMU InvenSense могут фильтровать измерения на аппаратном уровне при помощи фильтра нижних частот (LPF). Flix реализует собственный фильтр для гироскопа, чтобы иметь больше гибкости при поддержке разных IMU. Поэтому для встроенного LPF устанавливается максимальная частота среза:
+
+```cpp
+IMU.setDLPF(IMU.DLPF_MAX);
+```
+
+## Калибровка гироскопа
+
+Как и любое измерительное устройство, гироскоп вносит искажения в измерения. Наиболее простая модель этих искажений делит их на статические смещения (*bias*) и случайный шум (*noise*):
+
+\\[ gyro_{xyz}=rates_{xyz}+bias_{xyz}+noise \\]
+
+Для качественной работы подсистемы оценки ориентации и управления дроном необходимо оценить *bias* гироскопа и учесть его в вычислениях. Для этого при запуске программы производится калибровка гироскопа, которая реализована в функции `calibrateGyro()`. Эта функция считывает данные с гироскопа в состоянии покоя 1000 раз и усредняет их. Полученные значения считаются *bias* гироскопа и в дальнейшем вычитаются из измерений.
+
+Программа для вывода данных с гироскопа с калибровкой:
+
+```cpp
+#include <FlixPeriph.h>
+#include <SPI.h>
+
+MPU9250 IMU(SPI);
+
+float gyroBiasX, gyroBiasY, gyroBiasZ; // bias гироскопа
+
+void setup() {
+	Serial.begin(115200);
+	bool success = IMU.begin();
+	if (!success) {
+		Serial.println("Failed to initialize IMU");
+	}
+	calibrateGyro();
+}
+
+void loop() {
+	float gx, gy, gz;
+	IMU.waitForData();
+	IMU.getGyro(gx, gy, gz);
+
+	// Устранение bias гироскопа
+	gx -= gyroBiasX;
+	gy -= gyroBiasY;
+	gz -= gyroBiasZ;
+
+	Serial.printf("gx:%f gy:%f gz:%f\n", gx, gy, gz);
+	delay(50); // замедление вывода
+}
+
+void calibrateGyro() {
+	const int samples = 1000;
+	Serial.println("Calibrating gyro, stand still");
+
+	gyroBiasX = 0;
+	gyroBiasY = 0;
+	gyroBiasZ = 0;
+
+	// Получение 1000 измерений гироскопа
+	for (int i = 0; i < samples; i++) {
+		IMU.waitForData();
+		float gx, gy, gz;
+		IMU.getGyro(gx, gy, gz);
+		gyroBiasX += gx;
+		gyroBiasY += gy;
+		gyroBiasZ += gz;
+	}
+
+	// Усреднение значений
+	gyroBiasX = gyroBiasX / samples;
+	gyroBiasY = gyroBiasY / samples;
+	gyroBiasZ = gyroBiasZ / samples;
+
+	Serial.printf("Gyro bias X: %f\n", gyroBiasX);
+	Serial.printf("Gyro bias Y: %f\n", gyroBiasY);
+	Serial.printf("Gyro bias Z: %f\n", gyroBiasZ);
+}
+```
+
+График данных с гироскопа в состоянии покоя без калибровки. Можно увидеть статическую ошибку каждой из осей:
+
+<img src="img/gyro-uncalibrated-plotter.png">
+
+График данных с гироскопа в состоянии покоя после калибровки:
+
+<img src="img/gyro-calibrated-plotter.png">
+
+Откалиброванные данные с гироскопа вместе с данными с акселерометра поступают в *подсистему оценки состояния*.
+
+## Дополнительные материалы
+
+* [MPU-9250 datasheet](https://invensense.tdk.com/wp-content/uploads/2015/02/PS-MPU-9250A-01-v1.1.pdf).
+* [MPU-6500 datasheet](https://invensense.tdk.com/wp-content/uploads/2020/06/PS-MPU-6500A-01-v1.3.pdf).
+* [ICM-20948 datasheet](https://invensense.tdk.com/wp-content/uploads/2016/06/DS-000189-ICM-20948-v1.3.pdf).

docs/book/img

@@ -0,0 +1 @@
+../img

docs/build.md

@@ -1,12 +1,25 @@
 # 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
 
-Dependencies are [Gazebo Classic simulator](https://classic.gazebosim.org) and [SDL2](https://www.libsdl.org) library.
+### Ubuntu 20.04
 
-### Ubuntu
+The latest version of Ubuntu supported by Gazebo 11 simulator is 20.04. If you have a newer version, consider using a virtual machine.
 
-1. Install Gazebo 11:
+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
@@ -19,13 +32,19 @@ Dependencies are [Gazebo Classic simulator](https://classic.gazebosim.org) and [
    source ~/.bashrc
    ```
 
-2. Install SDL2:
+3. Install SDL2 and other dependencies:
 
    ```bash
-   sudo apt-get install libsdl2-dev
+   sudo apt-get update && sudo apt-get install build-essential libsdl2-dev
    ```
 
-3. Run the simulation:
+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
@@ -39,27 +58,60 @@ Dependencies are [Gazebo Classic simulator](https://classic.gazebosim.org) and [
    /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"
    ```
 
-2. Install Gazebo 11 and SDL2:
+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.
+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).
-2. Install ESP32 core using [Boards Manager](https://docs.arduino.cc/learn/starting-guide/cores).
-3. Build and upload the firmware using Arduino IDE.
+1. Install [Arduino IDE](https://www.arduino.cc/en/software) (version 2 is recommended).
+2. Install ESP32 core, version 3.0.7 (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.
+3. 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.
+4. Clone the project using git or [download the source code as a ZIP archive](https://codeload.github.com/okalachev/flix/zip/refs/heads/master).
+5. Open the downloaded Arduino sketch `flix/flix.ino` in Arduino IDE.
+6. [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)
 
@@ -84,3 +136,35 @@ Dependencies are [Gazebo Classic simulator](https://classic.gazebosim.org) and [
    ```
 
 See other available Make commands in the [Makefile](../Makefile).
+
+### Setup and flight
+
+Before flight you need to calibrate the accelerometer:
+
+1. Open Serial Monitor in Arduino IDE (use 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 (use use `make monitor` command in the command line).
+2. Type `cr` command there and follow the instructions.
+
+Then you can use your remote control to fly the drone!
+
+> [!NOTE]
+> If something goes wrong, go to the [Troubleshooting](troubleshooting.md) article.
+
+### Firmware code structure
+
+See [firmware overview](firmware.md) for more details.

docs/firmware.md

@@ -0,0 +1,37 @@
+# Firmware overview
+
+## Dataflow
+
+<img src="img/dataflow.svg" width=800 alt="Firmware dataflow diagram">
+
+The main loop is running at 1000 Hz. All the dataflow is happening through global variables (for simplicity):
+
+* `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.
+
+## Source files
+
+Firmware source files are located in `flix` directory. The key files are:
+
+* [`flix.ino`](../flix/flix.ino) — main entry point, Arduino sketch. Includes global variables definition 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.
+
+Utility files include:
+
+* [`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.
+
+## Building
+
+See build instructions in [build.md](build.md).

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+		<rect id="SVGID_00000077301502947632695740000005629016913768095395_" x="145.2" y="451" width="293.5" height="77"/>
+	</defs>
+	<clipPath id="SVGID_00000004518590643829462700000008680026774255780777_">
+		<use xlink:href="#SVGID_00000077301502947632695740000005629016913768095395_"  style="overflow:visible;"/>
+	</clipPath>
+	<g style="clip-path:url(#SVGID_00000004518590643829462700000008680026774255780777_);">
+		<text transform="matrix(1 0 0 1 197.8359 501.2101)" class="st5 st29">MPU9250 IMU</text>
+	</g>
+</g>
+</svg>

docs/js.js

@@ -0,0 +1,7 @@
+// Enable zoom on images larger than 300px
+document.querySelectorAll('.content img').forEach(function (img) {
+	var width = img.getAttribute('width');
+	if (!width || width >= 300) {
+		img.setAttribute('data-action', 'zoom');
+	}
+});

docs/log.md

@@ -0,0 +1,72 @@
+# Log analysis
+
+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:
+
+```bash
+make log
+```
+
+Logs are stored in `tools/log/*.csv` files.
+
+## Analysis
+
+### PlotJuggler
+
+The recommended tool for log analysis is PlotJuggler.
+
+<img src="img/plotjuggler.png" width="500">
+
+1. Install PlotJuggler using the [official instructions](https://github.com/facontidavide/PlotJuggler?tab=readme-ov-file#installation).
+
+2. Run PlotJuggler and drag'n'drop the downloaded log file there. Choose `t` column to be used as X axis.
+
+   You can open the most recent downloaded file using the command:
+
+   ```bash
+   make plot
+   ```
+
+   You can perform both log download and run PlotJuggler in one command:
+
+   ```bash
+   make log plot
+   ```
+
+### FlightPlot
+
+FlightPlot is a powerful tool for analyzing logs in [ULog format](https://docs.px4.io/main/en/dev_log/ulog_file_format.html). This format is used in PX4 and ArduPilot flight software.
+
+<img src="img/flightplot.png" width="500">
+
+1. [Install FlightPlot](https://github.com/PX4/FlightPlot).
+2. Flix repository contains a tool for converting CSV logs to ULog format. Build the tool using [the instructions](../tools/csv_to_ulog/README.md) and convert the log you want to analyze.
+3. Run FlightPlot and drag'n'drop the converted ULog-file there.
+
+### Foxglove Studio
+
+Foxglove is a tool for visualizing and analyzing robotics data with very rich functionality. It can import various formats, but mainly focuses on its own format, called [MCAP](https://mcap.dev).
+
+<img src="img/foxglove.png" width="500">
+
+1. Install Foxglove Studio from the [official website](https://foxglove.dev/download).
+
+2. Flix repository contains a tool for converting CSV logs to MCAP format. First, install its dependencies:
+
+   ```bash
+   cd tools
+   pip install -r requirements.txt
+   ```
+
+3. Convert the log you want to analyze:
+
+   ```bash
+   csv_to_mcap.py log_file.csv
+   ```
+
+4. Open the log in Foxglove Studio using *Open local file* command.

docs/theme/index.hbs

@@ -0,0 +1,336 @@
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+                {{/next}}
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+
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+
+        {{#if live_reload_endpoint}}
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+            const wsAddress = wsProtocol + "//" + location.host + "/" + "{{{live_reload_endpoint}}}";
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+                if (event.data === "reload") {
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+                    location.reload();
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+        {{/if}}
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+        <!-- Google Analytics Tag -->
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+        {{/if}}
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+    </body>
+</html>

docs/troubleshooting.md

@@ -0,0 +1,33 @@
+# Troubleshooting
+
+## The sketch doesn't compile
+
+Do the following:
+
+* **Check ESP32 core is installed**. Check if the version matches the one used in the [tutorial](build.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.
+
+## The drone doesn't fly
+
+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 if the CLI is working**. Perform `help` command in Serial Monitor. You should see the list of available commands.
+* **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.
+* **Check the IMU sample rate**. Perform `imu` command. The `rate` field should be about 1000 (Hz).
+* **Check the IMU data**. Perform `imu` command, check raw accelerometer and gyro output. The output should change as you move the drone.
+* **Calibrate the accelerometer.** if is wasn't done before. Type `ca` command in Serial Monitor and follow the instructions.
+* **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.
+* **Check the IMU orientation is set correctly**. If the attitude estimation is rotated, make sure `rotateIMU` function is defined correctly in `imu.ino` file.
+* **Check the motors**. Perform the following commands using Serial Monitor:
+  * `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).
+* **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 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/version0.md

@@ -0,0 +1,30 @@
+# Flix version 0
+
+Flix version 0 (obsolete):
+
+<img src="img/flix.jpg" width=500 alt="Flix quadcopter">
+
+## Components list
+
+|Type|Part|Image|Quantity|
+|-|-|-|-|
+|Microcontroller board|ESP32 Mini|<img src="img/esp32.jpg" width=100>|1|
+|IMU and barometer² board|GY-91 (or other MPU-9250 board)|<img src="img/gy-91.jpg" width=100>|1|
+|Quadcopter frame|K100|<img src="img/frame.jpg" width=100>|1|
+|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 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|||
+|Battery charger||<img src="img/charger.jpg" width=100>|1|
+|Wires, connectors, tape, ...||||
+
+*\* — not needed as ESP32 supports [software pin inversion](https://github.com/bolderflight/sbus#inverted-serial).*
+
+## Schematics
+
+<img src="img/schematics.svg" width=800 alt="Flix schematics">
+
+You can also check a user contributed [variant of complete circuit diagram](https://miro.com/app/board/uXjVN-dTjoo=/) of the drone.

docs/zoom.css

@@ -0,0 +1,31 @@
+img[data-action="zoom"] {
+  cursor: zoom-in;
+}
+.zoom-img,
+.zoom-img-wrap {
+  position: relative;
+  z-index: 666;
+  transition: all 300ms;
+}
+img.zoom-img {
+  cursor: zoom-out;
+}
+.zoom-overlay {
+  cursor: zoom-out;
+  z-index: 420;
+  background: #fff;
+  position: fixed;
+  top: 0;
+  left: 0;
+  right: 0;
+  bottom: 0;
+  filter: "alpha(opacity=0)";
+  opacity: 0;
+  transition:      opacity 300ms;
+}
+.zoom-overlay-open .zoom-overlay {
+  filter: "alpha(opacity=100)";
+  opacity: 1;
+}
+
+/*# sourceMappingURL=data:application/json;base64,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 */

docs/zoom.js

@@ -0,0 +1,281 @@
+/* https://github.com/spinningarrow/zoom-vanilla.js
+
+The MIT License
+
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of this software and associated documentation files (the
+"Software"), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+*/
+
++function () { "use strict";
+	var OFFSET = 80
+
+	// From http://youmightnotneedjquery.com/#offset
+	function offset(element) {
+		var rect = element.getBoundingClientRect()
+		var scrollTop = window.pageYOffset ||
+			document.documentElement.scrollTop ||
+			document.body.scrollTop ||
+			0
+		var scrollLeft = window.pageXOffset ||
+			document.documentElement.scrollLeft ||
+			document.body.scrollLeft ||
+			0
+		return {
+			top: rect.top + scrollTop,
+			left: rect.left + scrollLeft
+		}
+	}
+
+	function zoomListener() {
+		var activeZoom = null
+		var initialScrollPosition = null
+		var initialTouchPosition = null
+
+		function listen() {
+			document.body.addEventListener('click', function (event) {
+				if (event.target.getAttribute('data-action') !== 'zoom' ||
+					event.target.tagName !== 'IMG') return
+
+				zoom(event)
+			})
+		}
+
+		function zoom(event) {
+			event.stopPropagation()
+
+			if (document.body.classList.contains('zoom-overlay-open')) return
+
+			if (event.metaKey || event.ctrlKey) return openInNewWindow()
+
+			closeActiveZoom({ forceDispose: true })
+
+			activeZoom = vanillaZoom(event.target)
+			activeZoom.zoomImage()
+
+			addCloseActiveZoomListeners()
+		}
+
+		function openInNewWindow() {
+			window.open(event.target.getAttribute('data-original') ||
+				event.target.currentSrc ||
+				event.target.src,
+				'_blank')
+		}
+
+		function closeActiveZoom(options) {
+			options = options || { forceDispose: false }
+			if (!activeZoom) return
+
+			activeZoom[options.forceDispose ? 'dispose' : 'close']()
+			removeCloseActiveZoomListeners()
+			activeZoom = null
+		}
+
+		function addCloseActiveZoomListeners() {
+			// todo(fat): probably worth throttling this
+			window.addEventListener('scroll', handleScroll)
+			document.addEventListener('click', handleClick)
+			document.addEventListener('keyup', handleEscPressed)
+			document.addEventListener('touchstart', handleTouchStart)
+			document.addEventListener('touchend', handleClick)
+		}
+
+		function removeCloseActiveZoomListeners() {
+			window.removeEventListener('scroll', handleScroll)
+			document.removeEventListener('keyup', handleEscPressed)
+			document.removeEventListener('click', handleClick)
+			document.removeEventListener('touchstart', handleTouchStart)
+			document.removeEventListener('touchend', handleClick)
+		}
+
+		function handleScroll(event) {
+			if (initialScrollPosition === null) initialScrollPosition = window.pageYOffset
+			var deltaY = initialScrollPosition - window.pageYOffset
+			if (Math.abs(deltaY) >= 40) closeActiveZoom()
+		}
+
+		function handleEscPressed(event) {
+			if (event.keyCode == 27) closeActiveZoom()
+		}
+
+		function handleClick(event) {
+			event.stopPropagation()
+			event.preventDefault()
+			closeActiveZoom()
+		}
+
+		function handleTouchStart(event) {
+			initialTouchPosition = event.touches[0].pageY
+			event.target.addEventListener('touchmove', handleTouchMove)
+		}
+
+		function handleTouchMove(event) {
+			if (Math.abs(event.touches[0].pageY - initialTouchPosition) <= 10) return
+			closeActiveZoom()
+			event.target.removeEventListener('touchmove', handleTouchMove)
+		}
+
+		return { listen: listen }
+	}
+
+	var vanillaZoom = (function () {
+		var fullHeight = null
+		var fullWidth = null
+		var overlay = null
+		var imgScaleFactor = null
+
+		var targetImage = null
+		var targetImageWrap = null
+		var targetImageClone = null
+
+		function zoomImage() {
+			var img = document.createElement('img')
+			img.onload = function () {
+				fullHeight = Number(img.height)
+				fullWidth = Number(img.width)
+				zoomOriginal()
+			}
+			img.src = targetImage.currentSrc || targetImage.src
+		}
+
+		function zoomOriginal() {
+			targetImageWrap = document.createElement('div')
+			targetImageWrap.className = 'zoom-img-wrap'
+			targetImageWrap.style.position = 'absolute'
+			targetImageWrap.style.top = offset(targetImage).top + 'px'
+			targetImageWrap.style.left = offset(targetImage).left + 'px'
+
+			targetImageClone = targetImage.cloneNode()
+			targetImageClone.style.visibility = 'hidden'
+
+			targetImage.style.width = targetImage.offsetWidth + 'px'
+			targetImage.parentNode.replaceChild(targetImageClone, targetImage)
+
+			document.body.appendChild(targetImageWrap)
+			targetImageWrap.appendChild(targetImage)
+
+			targetImage.classList.add('zoom-img')
+			targetImage.setAttribute('data-action', 'zoom-out')
+
+			overlay = document.createElement('div')
+			overlay.className = 'zoom-overlay'
+
+			document.body.appendChild(overlay)
+
+			calculateZoom()
+			triggerAnimation()
+		}
+
+		function calculateZoom() {
+			targetImage.offsetWidth // repaint before animating
+
+			var originalFullImageWidth  = fullWidth
+			var originalFullImageHeight = fullHeight
+
+			var maxScaleFactor = originalFullImageWidth / targetImage.width
+
+			var viewportHeight = window.innerHeight - OFFSET
+			var viewportWidth  = window.innerWidth - OFFSET
+
+			var imageAspectRatio    = originalFullImageWidth / originalFullImageHeight
+			var viewportAspectRatio = viewportWidth / viewportHeight
+
+			if (originalFullImageWidth < viewportWidth && originalFullImageHeight < viewportHeight) {
+				imgScaleFactor = maxScaleFactor
+			} else if (imageAspectRatio < viewportAspectRatio) {
+				imgScaleFactor = (viewportHeight / originalFullImageHeight) * maxScaleFactor
+			} else {
+				imgScaleFactor = (viewportWidth / originalFullImageWidth) * maxScaleFactor
+			}
+		}
+
+		function triggerAnimation() {
+			targetImage.offsetWidth // repaint before animating
+
+			var imageOffset = offset(targetImage)
+			var scrollTop   = window.pageYOffset
+
+			var viewportY = scrollTop + (window.innerHeight / 2)
+			var viewportX = (window.innerWidth / 2)
+
+			var imageCenterY = imageOffset.top + (targetImage.height / 2)
+			var imageCenterX = imageOffset.left + (targetImage.width / 2)
+
+			var translateY = Math.round(viewportY - imageCenterY)
+			var translateX = Math.round(viewportX - imageCenterX)
+
+			var targetImageTransform = 'scale(' + imgScaleFactor + ')'
+			var targetImageWrapTransform =
+				'translate(' + translateX + 'px, ' + translateY + 'px) translateZ(0)'
+
+			targetImage.style.webkitTransform = targetImageTransform
+			targetImage.style.msTransform = targetImageTransform
+			targetImage.style.transform = targetImageTransform
+
+			targetImageWrap.style.webkitTransform = targetImageWrapTransform
+			targetImageWrap.style.msTransform = targetImageWrapTransform
+			targetImageWrap.style.transform = targetImageWrapTransform
+
+			document.body.classList.add('zoom-overlay-open')
+		}
+
+		function close() {
+			document.body.classList.remove('zoom-overlay-open')
+			document.body.classList.add('zoom-overlay-transitioning')
+
+			targetImage.style.webkitTransform = ''
+			targetImage.style.msTransform = ''
+			targetImage.style.transform = ''
+
+			targetImageWrap.style.webkitTransform = ''
+			targetImageWrap.style.msTransform = ''
+			targetImageWrap.style.transform = ''
+
+			if (!'transition' in document.body.style) return dispose()
+
+			targetImageWrap.addEventListener('transitionend', dispose)
+			targetImageWrap.addEventListener('webkitTransitionEnd', dispose)
+		}
+
+		function dispose() {
+			targetImage.removeEventListener('transitionend', dispose)
+			targetImage.removeEventListener('webkitTransitionEnd', dispose)
+
+			if (!targetImageWrap || !targetImageWrap.parentNode) return
+
+			targetImage.classList.remove('zoom-img')
+			targetImage.style.width = ''
+			targetImage.setAttribute('data-action', 'zoom')
+
+			targetImageClone.parentNode.replaceChild(targetImage, targetImageClone)
+			targetImageWrap.parentNode.removeChild(targetImageWrap)
+			overlay.parentNode.removeChild(overlay)
+
+			document.body.classList.remove('zoom-overlay-transitioning')
+		}
+
+		return function (target) {
+			targetImage = target
+			return { zoomImage: zoomImage, close: close, dispose: dispose }
+		}
+	}())
+
+	zoomListener().listen()
+}()

flix/cli.ino

@@ -19,72 +19,65 @@ const char* motd =
 "|__|     |_______||__| /__/ \\__\\\n\n"
 "Commands:\n\n"
 "help - show help\n"
-"show - show all parameters\n"
-"<name> <value> - set parameter\n"
+"p - show all parameters\n"
+"p <name> - show parameter\n"
+"p <name> <value> - set parameter\n"
+"preset - reset parameters\n"
 "ps - show pitch/roll/yaw\n"
 "psq - show attitude quaternion\n"
 "imu - show IMU data\n"
 "rc - show RC data\n"
-"mot - show motor data\n"
+"mot - show motor output\n"
 "log - dump in-RAM log\n"
+"cr - calibrate RC\n"
 "cg - calibrate gyro\n"
 "ca - calibrate accel\n"
-"fullmot <n> - test motor on all signals\n"
-"reset - reset drone's state\n";
+"mfr, mfl, mrr, mrl - test motor (remove props)\n"
+"reset - reset drone's state\n"
+"reboot - reboot the drone\n";
 
-const struct Param {
-	const char* name;
-	float* value;
-	float* value2;
-} params[] = {
-	{"rp", &rollRatePID.p, &pitchRatePID.p},
-	{"ri", &rollRatePID.i, &pitchRatePID.i},
-	{"rd", &rollRatePID.d, &pitchRatePID.d},
-
-	{"ap", &rollPID.p, &pitchPID.p},
-	{"ai", &rollPID.i, &pitchPID.i},
-	{"ad", &rollPID.d, &pitchPID.d},
-
-	{"yp", &yawRatePID.p, nullptr},
-	{"yi", &yawRatePID.i, nullptr},
-	{"yd", &yawRatePID.d, nullptr},
-
-	{"lpr", &ratesFilter.alpha, nullptr},
-	{"lpd", &rollRatePID.lpf.alpha, &pitchRatePID.lpf.alpha},
-
-	{"ss", &loopFreq, nullptr},
-	{"dt", &dt, nullptr},
-	{"t", &t, nullptr},
-};
-
-void doCommand(String& command, String& value)
-{
+void doCommand(String& command, String& arg0, String& arg1) {
 	if (command == "help" || command == "motd") {
 		Serial.println(motd);
-	} else if (command == "show") {
-		showTable();
+	} else if (command == "p" && arg0 == "") {
+		printParameters();
+	} else if (command == "p" && arg0 != "" && arg1 == "") {
+		Serial.printf("%s = %g\n", arg0.c_str(), getParameter(arg0.c_str()));
+	} else if (command == "p") {
+		bool success = setParameter(arg0.c_str(), arg1.toFloat());
+		if (success) {
+			Serial.printf("%s = %g\n", arg0.c_str(), arg1.toFloat());
+		} else {
+			Serial.printf("Parameter not found: %s\n", arg0.c_str());
+		}
+	} else if (command == "preset") {
+		resetParameters();
 	} else if (command == "ps") {
 		Vector a = attitude.toEulerZYX();
 		Serial.printf("roll: %f pitch: %f yaw: %f\n", a.x * RAD_TO_DEG, a.y * RAD_TO_DEG, a.z * RAD_TO_DEG);
 	} else if (command == "psq") {
 		Serial.printf("qx: %f qy: %f qz: %f qw: %f\n", attitude.x, attitude.y, attitude.z, attitude.w);
 	} else if (command == "imu") {
+		printIMUInfo();
 		Serial.printf("gyro: %f %f %f\n", rates.x, rates.y, rates.z);
 		Serial.printf("acc: %f %f %f\n", acc.x, acc.y, acc.z);
 		printIMUCal();
+		Serial.printf("rate: %f\n", loopRate);
 	} else if (command == "rc") {
-		Serial.printf("Raw: throttle %d yaw %d pitch %d roll %d aux %d mode %d\n",
+		Serial.printf("Raw: throttle %d yaw %d pitch %d roll %d armed %d mode %d\n",
 			channels[RC_CHANNEL_THROTTLE], channels[RC_CHANNEL_YAW], channels[RC_CHANNEL_PITCH],
-			channels[RC_CHANNEL_ROLL], channels[RC_CHANNEL_AUX], channels[RC_CHANNEL_MODE]);
-		Serial.printf("Control: throttle %f yaw %f pitch %f roll %f aux %f mode %f\n",
+			channels[RC_CHANNEL_ROLL], channels[RC_CHANNEL_ARMED], channels[RC_CHANNEL_MODE]);
+		Serial.printf("Control: throttle %f yaw %f pitch %f roll %f armed %f mode %f\n",
 			controls[RC_CHANNEL_THROTTLE], controls[RC_CHANNEL_YAW], controls[RC_CHANNEL_PITCH],
-			controls[RC_CHANNEL_ROLL], controls[RC_CHANNEL_AUX], controls[RC_CHANNEL_MODE]);
+			controls[RC_CHANNEL_ROLL], controls[RC_CHANNEL_ARMED], controls[RC_CHANNEL_MODE]);
 		Serial.printf("Mode: %s\n", getModeName());
 	} else if (command == "mot") {
 		Serial.printf("MOTOR front-right %f front-left %f rear-right %f rear-left %f\n",
 			motors[MOTOR_FRONT_RIGHT], motors[MOTOR_FRONT_LEFT], motors[MOTOR_REAR_RIGHT], motors[MOTOR_REAR_LEFT]);
 	} else if (command == "log") {
 		dumpLog();
+	} else if (command == "cr") {
+		calibrateRC();
 	} else if (command == "cg") {
 		calibrateGyro();
 	} else if (command == "ca") {
@@ -97,54 +90,31 @@ void doCommand(String& command, String& value)
 		cliTestMotor(MOTOR_REAR_RIGHT);
 	} else if (command == "mrl") {
 		cliTestMotor(MOTOR_REAR_LEFT);
-	} else if (command == "fullmot") {
-		fullMotorTest(value.toInt(), false);
 	} else if (command == "reset") {
 		attitude = Quaternion();
+	} else if (command == "reboot") {
+		ESP.restart();
+	} else if (command == "") {
+		// do nothing
 	} else {
-		float val = value.toFloat();
-		// TODO: on error returns 0, check invalid value
-
-		for (uint8_t i = 0; i < sizeof(params) / sizeof(params[0]); i++) {
-			if (command == params[i].name) {
-				*params[i].value = val;
-				if (params[i].value2 != nullptr) *params[i].value2 = val;
-				Serial.print(command);
-				Serial.print(" = ");
-				Serial.println(val, 4);
-				return;
-			}
-		}
 		Serial.println("Invalid command: " + command);
 	}
 }
 
-void showTable()
-{
-	for (uint8_t i = 0; i < sizeof(params) / sizeof(params[0]); i++) {
-		Serial.print(params[i].name);
-		Serial.print(" ");
-		Serial.println(*params[i].value, 5);
-	}
-}
-
-void cliTestMotor(uint8_t n)
-{
+void cliTestMotor(uint8_t n) {
 	Serial.printf("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
 	sendMotors();
-	delay(5000);
+	delay(3000);
 	motors[n] = 0;
 	sendMotors();
 	Serial.println("Done");
 }
 
-void parseInput()
-{
+void parseInput() {
 	static bool showMotd = true;
-	static String command;
-	static String value;
-	static bool parsingCommand = true;
+	static String input;
 
 	if (showMotd) {
 		Serial.println(motd);
@@ -154,16 +124,21 @@ void parseInput()
 	while (Serial.available()) {
 		char c = Serial.read();
 		if (c == '\n') {
-			parsingCommand = true;
-			if (!command.isEmpty()) {
-				doCommand(command, value);
-			}
-			command.clear();
-			value.clear();
-		} else if (c == ' ') {
-			parsingCommand = false;
+			char chars[input.length() + 1];
+			input.toCharArray(chars, input.length() + 1);
+			String command = stringToken(chars, " ");
+			String arg0 = stringToken(NULL, " ");
+			String arg1 = stringToken(NULL, "");
+			doCommand(command, arg0, arg1);
+			input.clear();
 		} else {
-			(parsingCommand ? command : value) += c;
+			input += c;
 		}
 	}
 }
+
+// Helper function for parsing input
+String stringToken(char* str, const char* delim) {
+	char* token = strtok(str, delim);
+	return token == NULL ? "" : token;
+}

flix/control.ino

@@ -27,15 +27,14 @@
 #define PITCH_I ROLL_I
 #define PITCH_D ROLL_D
 #define YAW_P 3
-#define PITCHRATE_MAX 360 * DEG_TO_RAD
-#define ROLLRATE_MAX 360 * DEG_TO_RAD
-#define YAWRATE_MAX 360 * DEG_TO_RAD
-#define MAX_TILT 30 * DEG_TO_RAD
+#define PITCHRATE_MAX radians(360)
+#define ROLLRATE_MAX radians(360)
+#define YAWRATE_MAX radians(360)
+#define MAX_TILT radians(30)
 
-#define RATES_LFP_ALPHA 0.8 // cutoff frequency ~ 250 Hz
 #define RATES_D_LPF_ALPHA 0.2 // cutoff frequency ~ 40 Hz
 
-enum { MANUAL, ACRO, STAB } mode = STAB;
+enum { MANUAL, ACRO, STAB, USER } mode = STAB;
 enum { YAW, YAW_RATE } yawMode = YAW;
 bool armed = false;
 
@@ -46,16 +45,14 @@ PID rollPID(ROLL_P, ROLL_I, ROLL_D);
 PID pitchPID(PITCH_P, PITCH_I, PITCH_D);
 PID yawPID(YAW_P, 0, 0);
 
-LowPassFilter<Vector> ratesFilter(RATES_LFP_ALPHA);
-
 Quaternion attitudeTarget;
 Vector ratesTarget;
 Vector torqueTarget;
 float thrustTarget;
 
-void control()
-{
+void control() {
 	interpretRC();
+	failsafe();
 	if (mode == STAB) {
 		controlAttitude();
 		controlRate();
@@ -68,38 +65,39 @@ void control()
 	}
 }
 
-void interpretRC()
-{
+void interpretRC() {
+	armed = controls[RC_CHANNEL_THROTTLE] >= 0.05 && controls[RC_CHANNEL_ARMED] >= 0.5;
+
+	// NOTE: put ACRO or MANUAL modes there if you want to use them
 	if (controls[RC_CHANNEL_MODE] < 0.25) {
-		mode = MANUAL;
+		mode = STAB;
 	} else if (controls[RC_CHANNEL_MODE] < 0.75) {
-		mode = ACRO;
+		mode = STAB;
 	} else {
 		mode = STAB;
 	}
 
-	armed = controls[RC_CHANNEL_THROTTLE] >= 0.05 && controls[RC_CHANNEL_AUX] >= 0.5;
 	thrustTarget = controls[RC_CHANNEL_THROTTLE];
 
 	if (mode == ACRO) {
 		yawMode = YAW_RATE;
 		ratesTarget.x = controls[RC_CHANNEL_ROLL] * ROLLRATE_MAX;
-		ratesTarget.y = -controls[RC_CHANNEL_PITCH] * PITCHRATE_MAX; // up pitch stick means tilt clockwise in frd
-		ratesTarget.z = controls[RC_CHANNEL_YAW] * YAWRATE_MAX;
+		ratesTarget.y = controls[RC_CHANNEL_PITCH] * PITCHRATE_MAX;
+		ratesTarget.z = -controls[RC_CHANNEL_YAW] * YAWRATE_MAX; // positive yaw stick means clockwise rotation in FLU
 
 	} else if (mode == STAB) {
 		yawMode = controls[RC_CHANNEL_YAW] == 0 ? YAW : YAW_RATE;
 
-		attitudeTarget = Quaternion::fromEulerZYX(
+		attitudeTarget = Quaternion::fromEulerZYX(Vector(
 			controls[RC_CHANNEL_ROLL] * MAX_TILT,
-			-controls[RC_CHANNEL_PITCH] * MAX_TILT,
-			attitudeTarget.getYaw());
-		ratesTarget.z = controls[RC_CHANNEL_YAW] * YAWRATE_MAX;
+			controls[RC_CHANNEL_PITCH] * MAX_TILT,
+			attitudeTarget.getYaw()));
+		ratesTarget.z = -controls[RC_CHANNEL_YAW] * YAWRATE_MAX; // positive yaw stick means clockwise rotation in FLU
 
 	} else if (mode == MANUAL) {
 		// passthrough mode
 		yawMode = YAW_RATE;
-		torqueTarget = Vector(controls[RC_CHANNEL_ROLL], -controls[RC_CHANNEL_PITCH], controls[RC_CHANNEL_YAW]) * 0.01;
+		torqueTarget = Vector(controls[RC_CHANNEL_ROLL], controls[RC_CHANNEL_PITCH], -controls[RC_CHANNEL_YAW]) * 0.01;
 	}
 
 	if (yawMode == YAW_RATE || !motorsActive()) {
@@ -108,8 +106,7 @@ void interpretRC()
 	}
 }
 
-void controlAttitude()
-{
+void controlAttitude() {
 	if (!armed) {
 		rollPID.reset();
 		pitchPID.reset();
@@ -117,7 +114,7 @@ void controlAttitude()
 		return;
 	}
 
-	const Vector up(0, 0, -1);
+	const Vector up(0, 0, 1);
 	Vector upActual = attitude.rotate(up);
 	Vector upTarget = attitudeTarget.rotate(up);
 
@@ -127,12 +124,12 @@ void controlAttitude()
 	ratesTarget.y = pitchPID.update(error.y, dt);
 
 	if (yawMode == YAW) {
-		ratesTarget.z = yawPID.update(wrapAngle(attitudeTarget.getYaw() - attitude.getYaw()), dt);
+		float yawError = wrapAngle(attitudeTarget.getYaw() - attitude.getYaw());
+		ratesTarget.z = yawPID.update(yawError, dt);
 	}
 }
 
-void controlRate()
-{
+void controlRate() {
 	if (!armed) {
 		rollRatePID.reset();
 		pitchRatePID.reset();
@@ -140,24 +137,24 @@ void controlRate()
 		return;
 	}
 
-	Vector ratesFiltered = ratesFilter.update(rates);
+	Vector error = ratesTarget - rates;
 
-	torqueTarget.x = rollRatePID.update(ratesTarget.x - ratesFiltered.x, dt); // un-normalized "torque"
-	torqueTarget.y = pitchRatePID.update(ratesTarget.y - ratesFiltered.y, dt);
-	torqueTarget.z = yawRatePID.update(ratesTarget.z - ratesFiltered.z, dt);
+	// 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);
 }
 
-void controlTorque()
-{
+void controlTorque() {
 	if (!armed) {
 		memset(motors, 0, sizeof(motors));
 		return;
 	}
 
-	motors[MOTOR_FRONT_LEFT] = thrustTarget + torqueTarget.y + torqueTarget.x - torqueTarget.z;
-	motors[MOTOR_FRONT_RIGHT] = thrustTarget + torqueTarget.y - torqueTarget.x + torqueTarget.z;
-	motors[MOTOR_REAR_LEFT] = thrustTarget - torqueTarget.y + torqueTarget.x + torqueTarget.z;
-	motors[MOTOR_REAR_RIGHT] = thrustTarget - torqueTarget.y - torqueTarget.x - torqueTarget.z;
+	motors[MOTOR_FRONT_LEFT] = thrustTarget + torqueTarget.x - torqueTarget.y + torqueTarget.z;
+	motors[MOTOR_FRONT_RIGHT] = thrustTarget - torqueTarget.x - torqueTarget.y - torqueTarget.z;
+	motors[MOTOR_REAR_LEFT] = thrustTarget + torqueTarget.x + torqueTarget.y - torqueTarget.z;
+	motors[MOTOR_REAR_RIGHT] = thrustTarget - torqueTarget.x + torqueTarget.y + torqueTarget.z;
 
 	motors[0] = constrain(motors[0], 0, 1);
 	motors[1] = constrain(motors[1], 0, 1);
@@ -165,17 +162,16 @@ void controlTorque()
 	motors[3] = constrain(motors[3], 0, 1);
 }
 
-bool motorsActive()
-{
+bool motorsActive() {
 	return motors[0] > 0 || motors[1] > 0 || motors[2] > 0 || motors[3] > 0;
 }
 
-const char* getModeName()
-{
+const char* getModeName() {
 	switch (mode) {
 		case MANUAL: return "MANUAL";
 		case ACRO: return "ACRO";
 		case STAB: return "STAB";
+		case USER: return "USER";
 		default: return "UNKNOWN";
 	}
 }

flix/estimate.ino

@@ -5,45 +5,40 @@
 
 #include "quaternion.h"
 #include "vector.h"
+#include "lpf.h"
 
-#define ONE_G 9.807f
-#define ACC_MIN 0.9f
-#define ACC_MAX 1.1f
 #define WEIGHT_ACC 0.5f
+#define RATES_LFP_ALPHA 0.2 // cutoff frequency ~ 40 Hz
 
-void estimate()
-{
+LowPassFilter<Vector> ratesFilter(RATES_LFP_ALPHA);
+
+void estimate() {
 	applyGyro();
 	applyAcc();
-	signalizeHorizontality();
 }
 
-void applyGyro()
-{
-	// applying gyro
+void applyGyro() {
+	// filter gyro to get angular rates
+	rates = ratesFilter.update(gyro);
+
+	// apply rates to attitude
 	attitude *= Quaternion::fromAngularRates(rates * dt);
 	attitude.normalize();
 }
 
-void applyAcc()
-{
+void applyAcc() {
 	// test should we apply accelerometer gravity correction
 	float accNorm = acc.norm();
 	bool landed = !motorsActive() && abs(accNorm - ONE_G) < ONE_G * 0.1f;
 
+	setLED(landed);
 	if (!landed) return;
 
 	// calculate accelerometer correction
-	Vector up = attitude.rotate(Vector(0, 0, -1));
+	Vector up = attitude.rotate(Vector(0, 0, 1));
 	Vector correction = Vector::angularRatesBetweenVectors(acc, up) * dt * WEIGHT_ACC;
 
 	// apply correction
 	attitude *= Quaternion::fromAngularRates(correction);
 	attitude.normalize();
 }
-
-void signalizeHorizontality()
-{
-	float angle = Vector::angleBetweenVectors(attitude.rotate(Vector(0, 0, -1)), Vector(0, 0, -1));
-	setLED(angle < 15 * DEG_TO_RAD);
-}

flix/failsafe.ino

@@ -0,0 +1,23 @@
+// Copyright (c) 2024 Oleg Kalachev <okalachev@gmail.com>
+// Repository: https://github.com/okalachev/flix
+
+// Fail-safe for RC loss
+
+#define RC_LOSS_TIMEOUT 0.2
+#define DESCEND_TIME 3.0 // time to descend from full throttle to zero
+
+void failsafe() {
+	if (t - controlsTime > RC_LOSS_TIMEOUT) {
+		descend();
+	}
+}
+
+void descend() {
+	// Smooth descend on RC lost
+	mode = STAB;
+	controls[RC_CHANNEL_ROLL] = 0;
+	controls[RC_CHANNEL_PITCH] = 0;
+	controls[RC_CHANNEL_YAW] = 0;
+	controls[RC_CHANNEL_THROTTLE] -= dt / DESCEND_TIME;
+	if (controls[RC_CHANNEL_THROTTLE] < 0) controls[RC_CHANNEL_THROTTLE] = 0;
+}

flix/flix.ino

@@ -8,35 +8,41 @@
 
 #define SERIAL_BAUDRATE 115200
 
-#define WIFI_ENABLED 0
+#define WIFI_ENABLED 1
 
-#define RC_CHANNELS 6
+#define RC_CHANNELS 16
+#define RC_CHANNEL_ROLL 0
+#define RC_CHANNEL_PITCH 1
 #define RC_CHANNEL_THROTTLE 2
 #define RC_CHANNEL_YAW 3
-#define RC_CHANNEL_PITCH 1
-#define RC_CHANNEL_ROLL 0
-#define RC_CHANNEL_AUX 4
+#define RC_CHANNEL_ARMED 4
 #define RC_CHANNEL_MODE 5
 
 #define MOTOR_REAR_LEFT 0
-#define MOTOR_FRONT_LEFT 3
-#define MOTOR_FRONT_RIGHT 2
 #define MOTOR_REAR_RIGHT 1
+#define MOTOR_FRONT_RIGHT 2
+#define MOTOR_FRONT_LEFT 3
+
+#define ONE_G 9.80665
 
 float t = NAN; // current step time, s
 float dt; // time delta from previous step, s
-float loopFreq; // loop frequency, Hz
-uint16_t channels[16]; // raw rc channels
+float loopRate; // loop rate, Hz
+int16_t channels[RC_CHANNELS]; // raw rc channels
 float controls[RC_CHANNELS]; // normalized controls in range [-1..1] ([0..1] for throttle)
-Vector rates; // angular rates, rad/s
+float controlsTime; // time of the last controls update
+Vector gyro; // gyroscope data
 Vector acc; // accelerometer data, m/s/s
+Vector rates; // filtered angular rates, rad/s
 Quaternion attitude; // estimated attitude
+bool landed; // are we landed and stationary
 float motors[4]; // normalized motors thrust in range [-1..1]
 
-void setup()
-{
+void setup() {
 	Serial.begin(SERIAL_BAUDRATE);
 	Serial.println("Initializing flix");
+	disableBrownOut();
+	setupParameters();
 	setupLED();
 	setupMotors();
 	setLED(true);
@@ -50,10 +56,8 @@ void setup()
 	Serial.println("Initializing complete");
 }
 
-void loop()
-{
-	if (!readIMU()) return;
-
+void loop() {
+	readIMU();
 	step();
 	readRC();
 	estimate();
@@ -61,7 +65,8 @@ void loop()
 	sendMotors();
 	parseInput();
 #if WIFI_ENABLED == 1
-	sendMavlink();
+	processMavlink();
 #endif
 	logData();
+	flushParameters();
 }

flix/imu.ino

@@ -6,100 +6,135 @@
 #include <SPI.h>
 #include <MPU9250.h>
 
-#define IMU_CS_PIN 4 // chip-select pin for IMU SPI connection
-#define CALIBRATE_GYRO_ON_START true
+MPU9250 IMU(SPI);
 
-MPU9250 IMU(SPI, IMU_CS_PIN);
+Vector accBias;
+Vector gyroBias;
+Vector accScale(1, 1, 1);
 
-void setupIMU()
-{
+void setupIMU() {
 	Serial.println("Setup IMU");
-
-	auto status = IMU.begin();
-	if (status < 0) {
+	bool status = IMU.begin();
+	if (!status) {
 		while (true) {
-			Serial.printf("IMU begin error: %d\n", status);
+			Serial.println("IMU begin error");
 			delay(1000);
 		}
 	}
-
-	if (CALIBRATE_GYRO_ON_START) {
-		calibrateGyro();
-	} else {
-		loadGyroCal();
+	configureIMU();
+	// calibrateGyro();
 }
 
-	loadAccelCal();
-
-	IMU.setSrd(0); // set sample rate to 1000 Hz
-	// NOTE: very important, without the above the rate would be terrible 50 Hz
+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);
 }
 
-bool readIMU()
-{
-	if (IMU.readSensor() < 0) {
-		Serial.println("IMU read error");
-		return false;
+void readIMU() {
+	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;
+	// rotate
+	rotateIMU(acc);
+	rotateIMU(gyro);
 }
 
-	auto lastRates = rates;
-
-	rates.x = IMU.getGyroX_rads();
-	rates.y = IMU.getGyroY_rads();
-	rates.z = IMU.getGyroZ_rads();
-	acc.x = IMU.getAccelX_mss();
-	acc.y = IMU.getAccelY_mss();
-	acc.z = IMU.getAccelZ_mss();
-
-	return rates != lastRates;
+void rotateIMU(Vector& data) {
+	// Rotate from LFD to FLU
+	// NOTE: In case of using other IMU orientation, change this line:
+	data = Vector(data.y, data.x, -data.z);
+	// Axes orientation for various boards: https://github.com/okalachev/flixperiph#imu-axes-orientation
 }
 
-void calibrateGyro()
-{
+void calibrateGyroOnce() {
+	if (!landed) return;
+	static float samples = 0; // overflows after 49 days at 1000 Hz
+	samples++;
+	gyroBias = gyroBias + (gyro - gyroBias) / samples; // running average
+}
+
+void calibrateGyro() {
+	const int samples = 1000;
 	Serial.println("Calibrating gyro, stand still");
-	delay(500);
-	int status = IMU.calibrateGyro();
-	Serial.printf("Calibration status: %d\n", status);
-	IMU.setSrd(0);
+	IMU.setGyroRange(IMU.GYRO_RANGE_250DPS); // the most sensitive mode
+
+	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();
 }
 
-void calibrateAccel()
-{
-	Serial.println("Cal accel: place level"); delay(3000);
-	IMU.calibrateAccel();
-	Serial.println("Cal accel: place nose up"); delay(3000);
-	IMU.calibrateAccel();
-	Serial.println("Cal accel: place nose down"); delay(3000);
-	IMU.calibrateAccel();
-	Serial.println("Cal accel: place on right side"); delay(3000);
-	IMU.calibrateAccel();
-	Serial.println("Cal accel: place on left side"); delay(3000);
-	IMU.calibrateAccel();
-	Serial.println("Cal accel: upside down"); delay(300);
-	IMU.calibrateAccel();
+void calibrateAccel() {
+	Serial.println("Calibrating accelerometer");
+	IMU.setAccelRange(IMU.ACCEL_RANGE_2G); // the most sensitive mode
+
+	Serial.setTimeout(60000);
+	Serial.print("Place level [enter] "); Serial.readStringUntil('\n');
+	calibrateAccelOnce();
+	Serial.print("Place nose up [enter] "); Serial.readStringUntil('\n');
+	calibrateAccelOnce();
+	Serial.print("Place nose down [enter] "); Serial.readStringUntil('\n');
+	calibrateAccelOnce();
+	Serial.print("Place on right side [enter] "); Serial.readStringUntil('\n');
+	calibrateAccelOnce();
+	Serial.print("Place on left side [enter] "); Serial.readStringUntil('\n');
+	calibrateAccelOnce();
+	Serial.print("Place upside down [enter] "); Serial.readStringUntil('\n');
+	calibrateAccelOnce();
+
 	printIMUCal();
+	configureIMU();
 }
 
-void loadAccelCal()
-{
-	// NOTE: this should be changed to the actual values
-	IMU.setAccelCalX(-0.0048542023, 1.0008112192);
-	IMU.setAccelCalY(0.0521845818, 0.9985780716);
-	IMU.setAccelCalZ(0.5754694939, 1.0045746565);
+void calibrateAccelOnce() {
+	const int samples = 1000;
+	static Vector accMax(-INFINITY, -INFINITY, -INFINITY);
+	static Vector accMin(INFINITY, INFINITY, INFINITY);
+
+	// Compute the average of the accelerometer readings
+	acc = Vector(0, 0, 0);
+	for (int i = 0; i < samples; i++) {
+		IMU.waitForData();
+		Vector sample;
+		IMU.getAccel(sample.x, sample.y, sample.z);
+		acc = acc + sample;
+	}
+	acc = acc / samples;
+
+	// Update the maximum and minimum values
+	if (acc.x > accMax.x) accMax.x = acc.x;
+	if (acc.y > accMax.y) accMax.y = acc.y;
+	if (acc.z > accMax.z) accMax.z = acc.z;
+	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;
+	Serial.printf("acc %f %f %f\n", acc.x, acc.y, acc.z);
+	Serial.printf("max %f %f %f\n", accMax.x, accMax.y, accMax.z);
+	Serial.printf("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 loadGyroCal()
-{
-	// NOTE: this should be changed to the actual values
-	IMU.setGyroBiasX_rads(-0.0185128022);
-	IMU.setGyroBiasY_rads(-0.0262369743);
-	IMU.setGyroBiasZ_rads(0.0163032326);
+void printIMUCal() {
+	Serial.printf("gyro bias: %f, %f, %f\n", gyroBias.x, gyroBias.y, gyroBias.z);
+	Serial.printf("accel bias: %f, %f, %f\n", accBias.x, accBias.y, accBias.z);
+	Serial.printf("accel scale: %f, %f, %f\n", accScale.x, accScale.y, accScale.z);
 }
 
-void printIMUCal()
-{
-	Serial.printf("gyro bias: %f %f %f\n", IMU.getGyroBiasX_rads(), IMU.getGyroBiasY_rads(), IMU.getGyroBiasZ_rads());
-	Serial.printf("accel bias: %f %f %f\n", IMU.getAccelBiasX_mss(), IMU.getAccelBiasY_mss(), IMU.getAccelBiasZ_mss());
-	Serial.printf("accel scale: %f %f %f\n", IMU.getAccelScaleFactorX(), IMU.getAccelScaleFactorY(), IMU.getAccelScaleFactorZ());
+void printIMUInfo() {
+	Serial.printf("model: %s\n", IMU.getModel());
+	Serial.printf("who am I: 0x%02X\n", IMU.whoAmI());
 }

flix/led.ino

@@ -1,21 +1,27 @@
 // Copyright (c) 2023 Oleg Kalachev <okalachev@gmail.com>
 // Repository: https://github.com/okalachev/flix
 
-// Main LED control
+// Board's LED control
 
 #define BLINK_PERIOD 500000
 
-void setupLED()
-{
+#ifndef LED_BUILTIN
+#define LED_BUILTIN 2 // for ESP32 Dev Module
+#endif
+
+void setupLED() {
 	pinMode(LED_BUILTIN, OUTPUT);
 }
 
-void setLED(bool on)
-{
+void setLED(bool on) {
+	static bool state = false;
+	if (on == state) {
+		return; // don't call digitalWrite if the state is the same
+	}
 	digitalWrite(LED_BUILTIN, on ? HIGH : LOW);
+	state = on;
 }
 
-void blinkLED()
-{
+void blinkLED() {
 	setLED(micros() / BLINK_PERIOD % 2);
 }

flix/log.ino

@@ -12,8 +12,7 @@
 float logBuffer[LOG_SIZE][LOG_COLUMNS]; // * 4 (float)
 int logPointer = 0;
 
-void logData()
-{
+void logData() {
 	if (!armed) return;
 
 	static float logTime = 0;
@@ -41,11 +40,11 @@ void logData()
 	}
 }
 
-void dumpLog()
-{
+void dumpLog() {
 	Serial.printf("t,rates.x,rates.y,rates.z,ratesTarget.x,ratesTarget.y,ratesTarget.z,"
 		"attitude.x,attitude.y,attitude.z,attitudeTarget.x,attitudeTarget.y,attitudeTarget.z,thrustTarget\n");
 	for (int i = 0; i < LOG_SIZE; i++) {
+		if (logBuffer[i][0] == 0) continue; // skip empty records
 		for (int j = 0; j < LOG_COLUMNS - 1; j++) {
 			Serial.printf("%f,", logBuffer[i][j]);
 		}

flix/lpf.h

@@ -6,16 +6,14 @@
 #pragma once
 
 template <typename T> // Using template to make the filter usable for scalar and vector values
-class LowPassFilter
-{
+class LowPassFilter {
 public:
 	float alpha; // smoothing constant, 1 means filter disabled
 	T output;
 
 	LowPassFilter(float alpha): alpha(alpha) {};
 
-	T update(const T input)
-	{
+	T update(const T input) {
 		if (alpha == 1) { // filter disabled
 			return input;
 		}
@@ -27,13 +25,11 @@ public:
 		return output = output * (1 - alpha) + input * alpha;
 	}
 
-	void setCutOffFrequency(float cutOffFreq, float dt)
-	{
+	void setCutOffFrequency(float cutOffFreq, float dt) {
 		alpha = 1 - exp(-2 * PI * cutOffFreq * dt);
 	}
 
-	void reset()
-	{
+	void reset() {
 		initialized = false;
 	}
 

flix/mavlink.ino

@@ -5,14 +5,20 @@
 
 #if WIFI_ENABLED == 1
 
-#include "mavlink/common/mavlink.h"
+#include <MAVLink.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
 
-void sendMavlink()
-{
+void processMavlink() {
+	sendMavlink();
+	receiveMavlink();
+}
+
+void sendMavlink() {
 	static float lastSlow = 0;
 	static float lastFast = 0;
 
@@ -23,7 +29,7 @@ void sendMavlink()
 		lastSlow = t;
 
 		mavlink_msg_heartbeat_pack(SYSTEM_ID, MAV_COMP_ID_AUTOPILOT1, &msg, MAV_TYPE_QUADROTOR,
-			MAV_AUTOPILOT_GENERIC, MAV_MODE_FLAG_MANUAL_INPUT_ENABLED | armed ? MAV_MODE_FLAG_SAFETY_ARMED : 0,
+			MAV_AUTOPILOT_GENERIC, MAV_MODE_FLAG_MANUAL_INPUT_ENABLED | (armed ? MAV_MODE_FLAG_SAFETY_ARMED : 0),
 			0, MAV_STATE_STANDBY);
 		sendMessage(&msg);
 	}
@@ -32,34 +38,133 @@ void sendMavlink()
 		lastFast = t;
 
 		const float zeroQuat[] = {0, 0, 0, 0};
+		Quaternion attitudeFRD = FLU2FRD(attitude); // MAVLink uses FRD coordinate system
 		mavlink_msg_attitude_quaternion_pack(SYSTEM_ID, MAV_COMP_ID_AUTOPILOT1, &msg,
-			time, attitude.w, attitude.x, attitude.y, attitude.z, rates.x, rates.y, rates.z, zeroQuat);
+			time, attitudeFRD.w, attitudeFRD.x, attitudeFRD.y, attitudeFRD.z, rates.x, rates.y, rates.z, zeroQuat);
 		sendMessage(&msg);
 
 		mavlink_msg_rc_channels_scaled_pack(SYSTEM_ID, MAV_COMP_ID_AUTOPILOT1, &msg, time, 0,
 			controls[0] * 10000, controls[1] * 10000, controls[2] * 10000,
 			controls[3] * 10000, controls[4] * 10000, controls[5] * 10000,
-			UINT16_MAX, UINT16_MAX, 255);
+			INT16_MAX, INT16_MAX, UINT8_MAX);
 		sendMessage(&msg);
 
 		float actuator[32];
-		memcpy(motors, actuator, 4 * sizeof(float));
+		memcpy(actuator, motors, sizeof(motors));
 		mavlink_msg_actuator_output_status_pack(SYSTEM_ID, MAV_COMP_ID_AUTOPILOT1, &msg, time, 4, actuator);
 		sendMessage(&msg);
 
 		mavlink_msg_scaled_imu_pack(SYSTEM_ID, MAV_COMP_ID_AUTOPILOT1, &msg, time,
 			acc.x * 1000, acc.y * 1000, acc.z * 1000,
-			rates.x * 1000, rates.y * 1000, rates.z * 1000,
+			gyro.x * 1000, gyro.y * 1000, gyro.z * 1000,
 			0, 0, 0, 0);
 		sendMessage(&msg);
 	}
 }
 
-inline void sendMessage(const void *msg)
-{
+void sendMessage(const void *msg) {
 	uint8_t buf[MAVLINK_MAX_PACKET_LEN];
-	uint16_t len = mavlink_msg_to_send_buffer(buf, (mavlink_message_t *)msg);
+	int len = mavlink_msg_to_send_buffer(buf, (mavlink_message_t *)msg);
 	sendWiFi(buf, len);
 }
 
+void receiveMavlink() {
+	uint8_t buf[MAVLINK_MAX_PACKET_LEN];
+	int len = receiveWiFi(buf, MAVLINK_MAX_PACKET_LEN);
+
+	// New packet, parse it
+	mavlink_message_t msg;
+	mavlink_status_t status;
+	for (int i = 0; i < len; i++) {
+		if (mavlink_parse_char(MAVLINK_COMM_0, buf[i], &msg, &status)) {
+			handleMavlink(&msg);
+		}
+	}
+}
+
+void handleMavlink(const void *_msg) {
+	mavlink_message_t *msg = (mavlink_message_t *)_msg;
+
+	if (msg->msgid == MAVLINK_MSG_ID_MANUAL_CONTROL) {
+		mavlink_manual_control_t manualControl;
+		mavlink_msg_manual_control_decode(msg, &manualControl);
+		controls[RC_CHANNEL_THROTTLE] = manualControl.z / 1000.0f;
+		controls[RC_CHANNEL_PITCH] = manualControl.x / 1000.0f * MAVLINK_CONTROL_SCALE;
+		controls[RC_CHANNEL_ROLL] = manualControl.y / 1000.0f * MAVLINK_CONTROL_SCALE;
+		controls[RC_CHANNEL_YAW] = manualControl.r / 1000.0f * MAVLINK_CONTROL_SCALE;
+		controls[RC_CHANNEL_MODE] = 1; // STAB mode
+		controls[RC_CHANNEL_ARMED] = 1; // armed
+		controlsTime = t;
+
+		if (abs(controls[RC_CHANNEL_YAW]) < MAVLINK_CONTROL_YAW_DEAD_ZONE) controls[RC_CHANNEL_YAW] = 0;
+	}
+
+	if (msg->msgid == MAVLINK_MSG_ID_PARAM_REQUEST_LIST) {
+		mavlink_message_t msg;
+		for (int i = 0; i < parametersCount(); i++) {
+			mavlink_msg_param_value_pack(SYSTEM_ID, MAV_COMP_ID_AUTOPILOT1, &msg,
+				getParameterName(i), getParameter(i), MAV_PARAM_TYPE_REAL32, parametersCount(), i);
+			sendMessage(&msg);
+		}
+	}
+
+	if (msg->msgid == MAVLINK_MSG_ID_PARAM_REQUEST_READ) {
+		mavlink_param_request_read_t paramRequestRead;
+		mavlink_msg_param_request_read_decode(msg, &paramRequestRead);
+		char name[16 + 1];
+		strlcpy(name, paramRequestRead.param_id, sizeof(name)); // param_id might be not null-terminated
+		float value = strlen(name) == 0 ? getParameter(paramRequestRead.param_index) : getParameter(name);
+		if (paramRequestRead.param_index != -1) {
+			memcpy(name, getParameterName(paramRequestRead.param_index), 16);
+		}
+		mavlink_message_t msg;
+		mavlink_msg_param_value_pack(SYSTEM_ID, MAV_COMP_ID_AUTOPILOT1, &msg,
+			name, value, MAV_PARAM_TYPE_REAL32, parametersCount(), paramRequestRead.param_index);
+		sendMessage(&msg);
+	}
+
+	if (msg->msgid == MAVLINK_MSG_ID_PARAM_SET) {
+		mavlink_param_set_t paramSet;
+		mavlink_msg_param_set_decode(msg, &paramSet);
+		char name[16 + 1];
+		strlcpy(name, paramSet.param_id, sizeof(name)); // param_id might be not null-terminated
+		setParameter(name, paramSet.param_value);
+		// send ack
+		mavlink_message_t msg;
+		mavlink_msg_param_value_pack(SYSTEM_ID, MAV_COMP_ID_AUTOPILOT1, &msg,
+			paramSet.param_id, paramSet.param_value, MAV_PARAM_TYPE_REAL32, parametersCount(), 0); // index is unknown
+		sendMessage(&msg);
+	}
+
+	if (msg->msgid == MAVLINK_MSG_ID_MISSION_REQUEST_LIST) { // handle to make qgc happy
+		mavlink_message_t msg;
+		mavlink_msg_mission_count_pack(SYSTEM_ID, MAV_COMP_ID_AUTOPILOT1, &msg, 0, 0, 0, MAV_MISSION_TYPE_MISSION, 0);
+		sendMessage(&msg);
+	}
+
+	// Handle commands
+	if (msg->msgid == MAVLINK_MSG_ID_COMMAND_LONG) {
+		mavlink_command_long_t commandLong;
+		mavlink_msg_command_long_decode(msg, &commandLong);
+		mavlink_message_t ack;
+		mavlink_message_t response;
+
+		if (commandLong.command == MAV_CMD_REQUEST_MESSAGE && commandLong.param1 == MAVLINK_MSG_ID_AUTOPILOT_VERSION) {
+			mavlink_msg_command_ack_pack(SYSTEM_ID, MAV_COMP_ID_AUTOPILOT1, &ack, commandLong.command, MAV_RESULT_ACCEPTED, UINT8_MAX, 0, msg->sysid, msg->compid);
+			sendMessage(&ack);
+			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, commandLong.command, MAV_RESULT_UNSUPPORTED, UINT8_MAX, 0, msg->sysid, msg->compid);
+			sendMessage(&ack);
+		}
+	}
+}
+
+// Convert Forward-Left-Up to Forward-Right-Down quaternion
+inline Quaternion FLU2FRD(const Quaternion &q) {
+	return Quaternion(q.w, q.x, -q.y, -q.z);
+}
+
 #endif

flix/motors.ino

@@ -1,75 +1,39 @@
 // Copyright (c) 2023 Oleg Kalachev <okalachev@gmail.com>
 // Repository: https://github.com/okalachev/flix
 
-// Motors output control
+// Motors output control using MOSFETs
+// In case of using ESC, use this version of the code: https://gist.github.com/okalachev/8871d3a94b6b6c0a298f41a4edd34c61.
 // Motor: 8520 3.7V
-// ESC: KINGDUO Micro Mini 4A 1S Brushed Esc 3.6-6V
 
-#define MOTOR_0_PIN 12
-#define MOTOR_1_PIN 13
-#define MOTOR_2_PIN 14
-#define MOTOR_3_PIN 15
+#define MOTOR_0_PIN 12 // rear left
+#define MOTOR_1_PIN 13 // rear right
+#define MOTOR_2_PIN 14 // front right
+#define MOTOR_3_PIN 15 // front left
 
 #define PWM_FREQUENCY 200
 #define PWM_RESOLUTION 8
 
-#define PWM_NEUTRAL 1500
-
-const uint16_t pwmMin[] = {1600, 1600, 1600, 1600};
-const uint16_t pwmMax[] = {2300, 2300, 2300, 2300};
-const uint16_t pwmReverseMin[] = {1390, 1440, 1440, 1440};
-const uint16_t pwmReverseMax[] = {1100, 1100, 1100, 1100};
-
 void setupMotors() {
 	Serial.println("Setup Motors");
 
-	// configure PWM channels
-	ledcSetup(0, PWM_FREQUENCY, PWM_RESOLUTION);
-	ledcSetup(1, PWM_FREQUENCY, PWM_RESOLUTION);
-	ledcSetup(2, PWM_FREQUENCY, PWM_RESOLUTION);
-	ledcSetup(3, PWM_FREQUENCY, PWM_RESOLUTION);
-
-	// attach channels to motor pins
-	ledcAttachPin(MOTOR_0_PIN, 0);
-	ledcAttachPin(MOTOR_1_PIN, 1);
-	ledcAttachPin(MOTOR_2_PIN, 2);
-	ledcAttachPin(MOTOR_3_PIN, 3);
+	// configure pins
+	ledcAttach(MOTOR_0_PIN, PWM_FREQUENCY, PWM_RESOLUTION);
+	ledcAttach(MOTOR_1_PIN, PWM_FREQUENCY, PWM_RESOLUTION);
+	ledcAttach(MOTOR_2_PIN, PWM_FREQUENCY, PWM_RESOLUTION);
+	ledcAttach(MOTOR_3_PIN, PWM_FREQUENCY, PWM_RESOLUTION);
 
 	sendMotors();
 	Serial.println("Motors initialized");
 }
 
-uint16_t getPWM(float val, int n)
-{
-	if (val == 0) {
-		return PWM_NEUTRAL;
-	} else if (val > 0) {
-		return mapff(val, 0, 1, pwmMin[n], pwmMax[n]);
-	} else {
-		return mapff(val, 0, -1, pwmReverseMin[n], pwmReverseMax[n]);
-	}
+uint8_t signalToDutyCycle(float control) {
+	float duty = mapff(control, 0, 1, 0, (1 << PWM_RESOLUTION) - 1);
+	return round(constrain(duty, 0, (1 << PWM_RESOLUTION) - 1));
 }
 
-uint8_t pwmToDutyCycle(uint16_t pwm) {
-	return map(pwm, 0, 1000000 / PWM_FREQUENCY, 0, (1 << PWM_RESOLUTION) - 1);
-}
-
-void sendMotors()
-{
-	ledcWrite(0, pwmToDutyCycle(getPWM(motors[0], 0)));
-	ledcWrite(1, pwmToDutyCycle(getPWM(motors[1], 1)));
-	ledcWrite(2, pwmToDutyCycle(getPWM(motors[2], 2)));
-	ledcWrite(3, pwmToDutyCycle(getPWM(motors[3], 3)));
-}
-
-void fullMotorTest(int n, bool reverse)
-{
-	printf("Full test for motor %d\n", n);
-	for (int pwm = PWM_NEUTRAL; pwm <= 2300 && pwm >= 700; pwm += reverse ? -100 : 100) {
-		printf("Motor %d: %d\n", n, pwm);
-		ledcWrite(n, pwmToDutyCycle(pwm));
-		delay(3000);
-	}
-	printf("Motor %d: %d\n", n, PWM_NEUTRAL);
-	ledcWrite(n, pwmToDutyCycle(PWM_NEUTRAL));
+void sendMotors() {
+	ledcWrite(MOTOR_0_PIN, signalToDutyCycle(motors[0]));
+	ledcWrite(MOTOR_1_PIN, signalToDutyCycle(motors[1]));
+	ledcWrite(MOTOR_2_PIN, signalToDutyCycle(motors[2]));
+	ledcWrite(MOTOR_3_PIN, signalToDutyCycle(motors[3]));
 }

flix/parameters.ino

@@ -0,0 +1,133 @@
+#pragma once
+
+#include <Preferences.h>
+#include <vector>
+
+extern float channelNeutral[RC_CHANNELS];
+extern float channelMax[RC_CHANNELS];
+
+Preferences storage;
+
+struct Parameter {
+	const char *name;
+	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},
+	// 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},
+	// 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_MAX_0", &channelMax[0]},
+	{"RC_MAX_1", &channelMax[1]},
+	{"RC_MAX_2", &channelMax[2]},
+	{"RC_MAX_3", &channelMax[3]},
+	{"RC_MAX_4", &channelMax[4]},
+	{"RC_MAX_5", &channelMax[5]},
+	{"RC_MAX_6", &channelMax[6]},
+	{"RC_MAX_7", &channelMax[7]}
+};
+
+void setupParameters() {
+	storage.begin("flix", false);
+	// Read parameters from storage
+	for (auto &parameter : parameters) {
+		if (!storage.isKey(parameter.name)) {
+			Serial.printf("Define new parameter %s = %f\n", parameter.name, *parameter.variable);
+			storage.putFloat(parameter.name, *parameter.variable);
+		}
+		*parameter.variable = storage.getFloat(parameter.name, *parameter.variable);
+		parameter.value = *parameter.variable;
+	}
+}
+
+int parametersCount() {
+	return sizeof(parameters) / sizeof(parameters[0]);
+}
+
+const char *getParameterName(int index) {
+	return parameters[index].name;
+}
+
+float getParameter(int index) {
+	return *parameters[index].variable;
+}
+
+float getParameter(const char *name) {
+	for (auto &parameter : parameters) {
+		if (strcmp(parameter.name, name) == 0) {
+			return *parameter.variable;
+		}
+	}
+	return NAN;
+}
+
+bool setParameter(const char *name, const float value) {
+	for (auto &parameter : parameters) {
+		if (strcmp(parameter.name, name) == 0) {
+			*parameter.variable = value;
+			return true;
+		}
+	}
+	return false;
+}
+
+void flushParameters() {
+	static float lastFlush = 0;
+	if (t - lastFlush < 1) return; // flush once per second
+	if (motorsActive()) return; // don't use flash while flying, it may cause a delay
+	lastFlush = t;
+
+	for (auto &parameter : parameters) {
+		if (parameter.value == *parameter.variable) continue;
+		if (isnan(parameter.value) && isnan(*parameter.variable)) continue; // handle NAN != NAN
+		storage.putFloat(parameter.name, *parameter.variable);
+		parameter.value = *parameter.variable;
+	}
+}
+
+void printParameters() {
+	for (auto &parameter : parameters) {
+		Serial.printf("%s = %g\n", parameter.name, *parameter.variable);
+	}
+}
+
+void resetParameters() {
+	storage.clear();
+	ESP.restart();
+}

flix/pid.h

@@ -7,8 +7,7 @@
 
 #include "lpf.h"
 
-class PID
-{
+class PID {
 public:
 	float p = 0;
 	float i = 0;
@@ -22,8 +21,7 @@ public:
 
 	PID(float p, float i, float d, float windup = 0, float dAlpha = 1) : p(p), i(i), d(d), windup(windup), lpf(dAlpha) {};
 
-	float update(float error, float dt)
-	{
+	float update(float error, float dt) {
 		integral += error * dt;
 
 		if (isfinite(prevError) && dt > 0) {
@@ -39,8 +37,7 @@ public:
 		return p * error + constrain(i * integral, -windup, windup) + d * derivative; // PID
 	}
 
-	void reset()
-	{
+	void reset() {
 		prevError = NAN;
 		integral = 0;
 		derivative = 0;

flix/quaternion.h

@@ -15,8 +15,7 @@ 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(float a, float b, float c, float angle) {
 		float halfAngle = angle * 0.5;
 		float sin2 = sin(halfAngle);
 		float cos2 = cos(halfAngle);
@@ -24,27 +23,20 @@ public:
 		return Quaternion(cos2, a * sinNorm, b * sinNorm, c * sinNorm);
 	}
 
-	static Quaternion fromAngularRates(float x, float y, float z)
-	{
-		return Quaternion::fromAxisAngle(x, y, z, sqrt(x * x + y * y + z * z));
-	}
-
-	static Quaternion fromAngularRates(const Vector& rates)
-	{
+	static Quaternion fromAngularRates(const Vector& rates) {
 		if (rates.zero()) {
 			return Quaternion();
 		}
 		return Quaternion::fromAxisAngle(rates.x, rates.y, rates.z, rates.norm());
 	}
 
-	static Quaternion fromEulerZYX(float x, float y, float z)
-	{
-		float cx = cos(x / 2);
-		float cy = cos(y / 2);
-		float cz = cos(z / 2);
-		float sx = sin(x / 2);
-		float sy = sin(y / 2);
-		float sz = sin(z / 2);
+	static Quaternion fromEulerZYX(const Vector& euler) {
+		float cx = cos(euler.x / 2);
+		float cy = cos(euler.y / 2);
+		float cz = cos(euler.z / 2);
+		float sx = sin(euler.x / 2);
+		float sy = sin(euler.y / 2);
+		float sz = sin(euler.z / 2);
 
 		return Quaternion(
 			cx * cy * cz + sx * sy * sz,
@@ -53,8 +45,7 @@ public:
 			cx * cy * sz - sx * sy * cz);
 	}
 
-	static Quaternion fromBetweenVectors(Vector u, Vector v)
-	{
+	static Quaternion fromBetweenVectors(Vector u, 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;
@@ -69,33 +60,46 @@ public:
 		return ret;
 	}
 
-	void toAxisAngle(float& a, float& b, float& c, float& angle)
-	{
+	void toAxisAngle(float& a, float& b, float& c, float& angle) {
 		angle = acos(w) * 2;
 		a = x / sin(angle / 2);
 		b = y / sin(angle / 2);
 		c = z / sin(angle / 2);
 	}
 
-	Vector toEulerZYX() const
-	{
-		return Vector(
-			atan2(2 * (w * x + y * z), 1 - 2 * (x * x + y * y)),
-			asin(2 * (w * y - z * x)),
-			atan2(2 * (w * z + x * y), 1 - 2 * (y * y + z * z)));
+	Vector toEulerZYX() const {
+		// https://github.com/ros/geometry2/blob/589caf083cae9d8fae7effdb910454b4681b9ec1/tf2/include/tf2/impl/utils.h#L87
+		Vector euler;
+		float sqx = x * x;
+		float sqy = y * y;
+		float sqz = z * z;
+		float sqw = w * w;
+		// Cases derived from https://orbitalstation.wordpress.com/tag/quaternion/
+		float sarg = -2 * (x * z - w * y) / (sqx + sqy + sqz + sqw);
+		if (sarg <= -0.99999) {
+			euler.x = 0;
+			euler.y = -0.5 * PI;
+			euler.z = -2 * atan2(y, x);
+		} else if (sarg >= 0.99999) {
+			euler.x = 0;
+			euler.y = 0.5 * PI;
+			euler.z = 2 * atan2(y, x);
+		} else {
+			euler.x = atan2(2 * (y * z + w * x), sqw - sqx - sqy + sqz);
+			euler.y = asin(sarg);
+			euler.z = atan2(2 * (x * y + w * z), sqw + sqx - sqy - sqz);
+		}
+		return euler;
 	}
 
-	float getYaw() const
-	{
+	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) {
@@ -106,15 +110,14 @@ public:
 		return yaw;
 	}
 
-	void setYaw(float yaw)
-	{
+	void setYaw(float yaw) {
 		// TODO: optimize?
 		Vector euler = toEulerZYX();
-		(*this) = Quaternion::fromEulerZYX(euler.x, euler.y, yaw);
+		euler.z = yaw;
+		(*this) = Quaternion::fromEulerZYX(euler);
 	}
 
-	Quaternion& operator *= (const Quaternion& q)
-	{
+	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,
@@ -123,8 +126,7 @@ public:
 		return (*this = ret);
 	}
 
-	Quaternion operator * (const Quaternion& q)
-	{
+	Quaternion operator * (const Quaternion& q) {
 		return Quaternion(
 			w * q.w - x * q.x - y * q.y - z * q.z,
 			w * q.x + x * q.w + y * q.z - z * q.y,
@@ -132,8 +134,7 @@ public:
 			w * q.z + z * q.w + x * q.y - y * q.x);
 	}
 
-	Quaternion inversed() const
-	{
+	Quaternion inversed() const {
 		float normSqInv = 1 / (w * w + x * x + y * y + z * z);
 		return Quaternion(
 			w * normSqInv,
@@ -142,13 +143,11 @@ public:
 			-z * normSqInv);
 	}
 
-	float norm() const
-	{
+	float norm() const {
 		return sqrt(w * w + x * x + y * y + z * z);
 	}
 
-	void normalize()
-	{
+	void normalize() {
 		float n = norm();
 		w /= n;
 		x /= n;
@@ -156,27 +155,24 @@ public:
 		z /= n;
 	}
 
-	Vector conjugate(const Vector& v)
-	{
+	Vector conjugate(const Vector& v) {
 		Quaternion qv(0, v.x, v.y, v.z);
 		Quaternion res = (*this) * qv * inversed();
 		return Vector(res.x, res.y, res.z);
 	}
 
-	Vector conjugateInversed(const Vector& v)
-	{
+	Vector conjugateInversed(const Vector& v) {
 		Quaternion qv(0, v.x, v.y, v.z);
 		Quaternion res = inversed() * qv * (*this);
 		return Vector(res.x, res.y, res.z);
 	}
 
-	inline Vector rotate(const Vector& v)
-	{
+	// Rotate vector by quaternion
+	inline Vector rotate(const Vector& v) {
 		return conjugateInversed(v);
 	}
 
-	inline bool finite() const
-	{
+	inline bool finite() const {
 		return isfinite(w) && isfinite(x) && isfinite(y) && isfinite(z);
 	}
 

flix/rc.ino

@@ -5,29 +5,51 @@
 
 #include <SBUS.h>
 
-const uint16_t channelNeutral[] = {995, 883, 200, 972, 512, 512};
-const uint16_t channelMax[] = {1651, 1540, 1713, 1630, 1472, 1472};
+float channelNeutral[RC_CHANNELS] = {NAN}; // first element NAN means not calibrated
+float channelMax[RC_CHANNELS];
 
-SBUS RC(Serial2);
+SBUS RC(Serial2); // NOTE: Use RC(Serial2, 16, 17) if you use the old UART2 pins
 
-void setupRC()
-{
+void setupRC() {
 	Serial.println("Setup RC");
 	RC.begin();
 }
 
-void readRC()
-{
-	bool failSafe, lostFrame;
-	if (RC.read(channels, &failSafe, &lostFrame)) {
-		if (failSafe) { return; } // TODO:
-		if (lostFrame) { return; }
+void readRC() {
+	if (RC.read()) {
+		SBUSData data = RC.data();
+		memcpy(channels, data.ch, sizeof(channels)); // copy channels data
 		normalizeRC();
+		controlsTime = t;
 	}
 }
 
-static void normalizeRC() {
+void normalizeRC() {
+	if (isnan(channelNeutral[0])) return; // skip if not calibrated
 	for (uint8_t i = 0; i < RC_CHANNELS; i++) {
 		controls[i] = mapf(channels[i], channelNeutral[i], channelMax[i], 0, 1);
 	}
 }
+
+void calibrateRC() {
+	Serial.println("Calibrate RC: move all sticks to maximum positions within 4 seconds");
+	Serial.println("··o     ··o\n···     ···\n···     ···");
+	delay(4000);
+	for (int i = 0; i < 30; i++) readRC(); // ensure the values are updated
+	for (int i = 0; i < RC_CHANNELS; i++) {
+		channelMax[i] = channels[i];
+	}
+	Serial.println("Calibrate RC: move all sticks to neutral positions within 4 seconds");
+	Serial.println("···     ···\n···     ·o·\n·o·     ···");
+	delay(4000);
+	for (int i = 0; i < 30; i++) readRC(); // ensure the values are updated
+	for (int i = 0; i < RC_CHANNELS; i++) {
+		channelNeutral[i] = channels[i];
+	}
+	printRCCal();
+}
+
+void printRCCal() {
+	printArray(channelNeutral, RC_CHANNELS);
+	printArray(channelMax, RC_CHANNELS);
+}

flix/time.ino

@@ -3,8 +3,7 @@
 
 // Time related functions
 
-void step()
-{
+void step() {
 	float now = micros() / 1000000.0;
 	dt = now - t;
 	t = now;
@@ -13,17 +12,16 @@ void step()
 		dt = 0; // assume dt to be zero on first step and on reset
 	}
 
-	computeLoopFreq();
+	computeLoopRate();
 }
 
-void computeLoopFreq()
-{
+void computeLoopRate() {
 	static float windowStart = 0;
-	static uint32_t freq = 0;
-	freq++;
+	static uint32_t rate = 0;
+	rate++;
 	if (t - windowStart >= 1) { // 1 second window
-		loopFreq = freq;
+		loopRate = rate;
 		windowStart = t;
-		freq = 0;
+		rate = 0;
 	}
 }

flix/util.ino

@@ -3,31 +3,20 @@
 
 // Utility functions
 
-#include "math.h"
+#include <math.h>
+#include <soc/soc.h>
+#include <soc/rtc_cntl_reg.h>
 
-float mapf(long x, long in_min, long in_max, float out_min, float out_max)
-{
+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 mapff(float x, float in_min, float in_max, float out_min, float out_max)
-{
+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;
 }
 
-int8_t sign(float x)
-{
-	return (x > 0) - (x < 0);
-}
-
-float randomFloat(float min, float max)
-{
-	return min + (max - min) * (float)rand() / RAND_MAX;
-}
-
-// wrap angle to [-PI, PI)
-float wrapAngle(float angle)
-{
+// Wrap angle to [-PI, PI)
+float wrapAngle(float angle) {
 	angle = fmodf(angle, 2 * PI);
 	if (angle > PI) {
 		angle -= 2 * PI;
@@ -36,3 +25,18 @@ float wrapAngle(float angle)
 	}
 	return angle;
 }
+
+template <typename T>
+void printArray(T arr[], int size) {
+	Serial.print("{");
+	for (uint8_t i = 0; i < size; i++) {
+		Serial.print(arr[i]);
+		if (i < size - 1) Serial.print(", ");
+	}
+	Serial.println("}");
+}
+
+// Disable reset on low voltage
+void disableBrownOut() {
+	WRITE_PERI_REG(RTC_CNTL_BROWN_OUT_REG, 0);
+}

flix/vector.h

@@ -5,8 +5,7 @@
 
 #pragma once
 
-class Vector : public Printable
-{
+class Vector : public Printable {
 public:
 	float x, y, z;
 
@@ -14,79 +13,79 @@ public:
 
 	Vector(float x, float y, float z): x(x), y(y), z(z) {};
 
-	float norm() const
-	{
+	float norm() const {
 		return sqrt(x * x + y * y + z * z);
 	}
 
-	bool zero() const
-	{
+	bool zero() const {
 		return x == 0 && y == 0 && z == 0;
 	}
 
-	void normalize()
-	{
+	void normalize() {
 		float n = norm();
 		x /= n;
 		y /= n;
 		z /= n;
 	}
 
-	Vector operator * (const float b) const
-	{
+	Vector operator * (const float b) const {
 		return Vector(x * b, y * b, z * b);
 	}
 
-	Vector operator / (const float b) const
-	{
+	Vector operator / (const float b) const {
 		return Vector(x / b, y / b, z / b);
 	}
 
-	Vector operator + (const Vector& b) const
-	{
+	Vector operator + (const Vector& b) const {
 		return Vector(x + b.x, y + b.y, z + b.z);
 	}
 
-	Vector operator - (const Vector& b) const
-	{
+	Vector operator - (const Vector& b) const {
 		return Vector(x - b.x, y - b.y, z - b.z);
 	}
 
-	inline bool operator == (const Vector& b) const
-	{
+	// Element-wise multiplication
+	Vector operator * (const Vector& b) const {
+		return Vector(x * b.x, y * b.y, z * b.z);
+	}
+
+	// Element-wise division
+	Vector operator / (const Vector& b) const {
+		return Vector(x / b.x, y / b.y, z / b.z);
+	}
+
+	inline bool operator == (const Vector& b) const {
 		return x == b.x && y == b.y && z == b.z;
 	}
 
-	inline bool operator != (const Vector& b) const
-	{
+	inline bool operator != (const Vector& b) const {
 		return !(*this == b);
 	}
 
-	inline bool finite() const
-	{
+	inline bool finite() const {
 		return isfinite(x) && isfinite(y) && isfinite(z);
 	}
 
-	static float dot(const Vector& a, const Vector& b)
-	{
+	static float dot(const Vector& a, const Vector& b) {
 		return a.x * b.x + a.y * b.y + a.z * b.z;
 	}
 
-	static Vector cross(const Vector& a, const Vector& b)
-	{
+	static Vector cross(const Vector& a, const Vector& b) {
 		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 angleBetweenVectors(const Vector& a, const Vector& b) {
 		return acos(constrain(dot(a, b) / (a.norm() * b.norm()), -1, 1));
 	}
 
-	static Vector angularRatesBetweenVectors(const Vector& u, const Vector& v)
-	{
-		Vector direction = cross(u, v);
+	static Vector angularRatesBetweenVectors(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(u, v);
+		float angle = angleBetweenVectors(a, b);
 		return direction * angle;
 	}
 

flix/wifi.ino

@@ -6,10 +6,8 @@
 #if WIFI_ENABLED == 1
 
 #include <WiFi.h>
-#include <WiFiClient.h>
 #include <WiFiAP.h>
-#include "SBUS.h"
-#include "mavlink/common/mavlink.h"
+#include <WiFiUdp.h>
 
 #define WIFI_SSID "flix"
 #define WIFI_PASSWORD "flixwifi"
@@ -18,18 +16,22 @@
 
 WiFiUDP udp;
 
-void setupWiFi()
-{
+void setupWiFi() {
 	Serial.println("Setup Wi-Fi");
 	WiFi.softAP(WIFI_SSID, WIFI_PASSWORD);
 	IPAddress myIP = WiFi.softAPIP();
+	udp.begin(WIFI_UDP_PORT);
 }
 
-inline void sendWiFi(const uint8_t *buf, size_t len)
-{
+void sendWiFi(const uint8_t *buf, int len) {
 	udp.beginPacket(WIFI_UDP_IP, WIFI_UDP_PORT);
 	udp.write(buf, len);
 	udp.endPacket();
 }
 
+int receiveWiFi(uint8_t *buf, int len) {
+	udp.parsePacket();
+	return udp.read(buf, len);
+}
+
 #endif

gazebo/Arduino.h

@@ -7,6 +7,7 @@
 
 #include <cmath>
 #include <string>
+#include <stdint.h>
 #include <stdio.h>
 #include <unistd.h>
 #include <sys/poll.h>
@@ -14,6 +15,8 @@
 #define PI 3.1415926535897932384626433832795
 #define DEG_TO_RAD 0.017453292519943295769236907684886
 #define RAD_TO_DEG 57.295779513082320876798154814105
+#define radians(deg) ((deg)*DEG_TO_RAD)
+#define degrees(rad) ((rad)*RAD_TO_DEG)
 
 #define constrain(amt,low,high) ((amt)<(low)?(low):((amt)>(high)?(high):(amt)))
 
@@ -24,15 +27,27 @@ long map(long x, long in_min, long in_max, long out_min, long out_max) {
 	return (delta * rise) / run + out_min;
 }
 
+size_t strlcpy(char* dst, const char* src, size_t len) {
+	size_t l = strlen(src);
+	size_t i = 0;
+	while (i < len - 1 && *src != '\0') { *dst++ = *src++; i++; }
+	*dst = '\0';
+	return l;
+}
+
 class __FlashStringHelper;
 
 // Arduino String partial implementation
 // https://www.arduino.cc/reference/en/language/variables/data-types/stringobject/
 class String: public std::string {
 public:
+	String(const char *str = "") : std::string(str) {}
 	long toInt() const { return atol(this->c_str()); }
 	float toFloat() const { return atof(this->c_str()); }
 	bool isEmpty() const { return this->empty(); }
+	void toCharArray(char *buf, unsigned int bufsize, unsigned int index = 0) const {
+		strlcpy(buf, this->c_str() + index, bufsize);
+	}
 };
 
 class Print;
@@ -44,8 +59,7 @@ public:
 
 class Print {
 public:
-	size_t printf(const char *format, ...)
-	{
+	size_t printf(const char *format, ...) {
 		va_list args;
 		va_start(args, format);
 		size_t result = vprintf(format, args);
@@ -53,48 +67,43 @@ public:
 		return result;
 	}
 
-	size_t print(float n, int digits = 2)
-	{
+	size_t print(int n) {
+		return printf("%d", n);
+	}
+
+	size_t print(float n, int digits = 2) {
 		return printf("%.*f", digits, n);
 	}
 
-	size_t println(float n, int digits = 2)
-	{
+	size_t println(float n, int digits = 2) {
 		return printf("%.*f\n", digits, n);
 	}
 
-	size_t print(const char* s)
-	{
+	size_t print(const char* s) {
 		return printf("%s", s);
 	}
 
-	size_t println()
-	{
+	size_t println() {
 		return print("\n");
 	}
 
-	size_t println(const char* s)
-	{
+	size_t println(const char* s) {
 		return printf("%s\n", s);
 	}
 
-	size_t println(const Printable& p)
-	{
+	size_t println(const Printable& p) {
 		return p.printTo(*this) + print("\n");
 	}
 
-	size_t print(const String& s)
-	{
+	size_t print(const String& s) {
 		return printf("%s", s.c_str());
 	}
 
-	size_t println(const std::string& s)
-	{
+	size_t println(const std::string& s) {
 		return printf("%s\n", s.c_str());
 	}
 
-	size_t println(const String& s)
-	{
+	size_t println(const String& s) {
 		return printf("%s\n", s.c_str());
 	}
 };
@@ -120,22 +129,30 @@ public:
 	int read() {
 		if (available()) {
 			char c;
-			::read(STDIN_FILENO, &c, 1); // use raw read to avoid C++ buffering
+			size_t res = ::read(STDIN_FILENO, &c, 1); // use raw read to avoid C++ buffering
 			// https://stackoverflow.com/questions/45238997/does-getchar-function-has-its-own-buffer-to-store-remaining-input
 			return c;
 		}
 		return -1;
 	}
+
+	void setRxInvert(bool invert) {};
 };
 
 HardwareSerial Serial, Serial2;
 
+class EspClass {
+public:
+	void restart() { Serial.println("Ignore reboot in simulation"); }
+} ESP;
+
 void delay(uint32_t ms) {
 	std::this_thread::sleep_for(std::chrono::milliseconds(ms));
 }
 
 unsigned long __micros;
+unsigned long __resetTime = 0;
 
 unsigned long micros() {
-	return __micros;
+	return __micros + __resetTime; // keep the time monotonic
 }

gazebo/CMakeLists.txt

@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.0 FATAL_ERROR)
+cmake_minimum_required(VERSION 3.5 FATAL_ERROR)
 project(flix_gazebo)
 
 # === gazebo plugin
@@ -10,9 +10,13 @@ list(APPEND CMAKE_CXX_FLAGS "${GAZEBO_CXX_FLAGS}")
 
 set(FLIX_SOURCE_DIR ../flix)
 include_directories(${FLIX_SOURCE_DIR})
-file(GLOB_RECURSE FLIX_INO_FILES ${FLIX_SOURCE_DIR}/*.ino)
 
 set(CMAKE_BUILD_TYPE RelWithDebInfo)
-add_library(flix SHARED flix.cpp)
+add_library(flix SHARED simulator.cpp)
 target_link_libraries(flix ${GAZEBO_LIBRARIES} ${SDL2_LIBRARIES})
 target_include_directories(flix PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})
+target_compile_options(flix PRIVATE -Wno-address-of-packed-member) # disable unneeded mavlink warnings
+
+# Include dir for MAVLink-Arduino library
+target_include_directories(flix PUBLIC $ENV{HOME}/Arduino/libraries/MAVLink)
+target_include_directories(flix PUBLIC $ENV{HOME}/Documents/Arduino/libraries/MAVLink)

gazebo/Preferences.h

@@ -0,0 +1,63 @@
+// Copyright (c) 2024 Oleg Kalachev <okalachev@gmail.com>
+// Repository: https://github.com/okalachev/flix
+
+// Partial implementation of the ESP32 Preferences library for the simulation
+
+#include <map>
+#include <fstream>
+#include "util.h"
+
+class Preferences {
+private:
+	std::map<std::string, float> storage;
+	std::string storagePath;
+
+	void readFromFile() {
+		std::ifstream file(storagePath);
+		std::string key;
+		float value;
+		while (file >> key >> value) {
+			storage[key] = value;
+		}
+	}
+
+	void writeToFile() {
+		std::ofstream file(storagePath);
+		for (auto &pair : storage) {
+			file << pair.first << " " << pair.second << std::endl;
+		}
+	}
+
+public:
+	bool begin(const char *name, bool readOnly = false, const char *partition_label = NULL) {
+		storagePath = getPluginPath().parent_path() / (std::string(name) + ".txt");
+		gzmsg << "Preferences initialized: " << storagePath << std::endl;
+		readFromFile();
+		return true;
+	}
+
+	void end();
+
+	bool isKey(const char *key) {
+		return storage.find(key) != storage.end();
+	}
+
+	size_t putFloat(const char *key, float value) {
+		storage[key] = value;
+		writeToFile();
+		return sizeof(value);
+	}
+
+	float getFloat(const char *key, float defaultValue = NAN) {
+		if (!isKey(key)) {
+			return defaultValue;
+		}
+		return storage[key];
+	}
+
+	bool clear() {
+		storage.clear();
+		writeToFile();
+		return true;
+	}
+};

gazebo/README.md

@@ -0,0 +1,15 @@
+# Gazebo Simulation
+
+<img src="../docs/img/simulator.png" width=500 alt="Flix simulator">
+
+## Building and running
+
+See [building and running instructions](../docs/build.md#simulation).
+
+## Code structure
+
+Flix simulator is based on [Gazebo Classic](https://classic.gazebosim.org) and consists of the following components:
+
+* Physical model of the drone: [`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.

gazebo/SBUS.h

@@ -0,0 +1,23 @@
+// Copyright (c) 2023 Oleg Kalachev <okalachev@gmail.com>
+// Repository: https://github.com/okalachev/flix
+
+// SBUS library mock to make it possible to compile simulator with rc.ino
+
+#include "joystick.h"
+
+struct SBUSData {
+	int16_t ch[16];
+};
+
+class SBUS {
+public:
+	SBUS(HardwareSerial& bus, const bool inv = true) {};
+	SBUS(HardwareSerial& bus, const int8_t rxpin, const int8_t txpin, const bool inv = true) {};
+	void begin() {};
+	bool read() { return joystickInitialized; };
+	SBUSData data() {
+		SBUSData data;
+		joystickGet(data.ch);
+		return data;
+	};
+};

gazebo/flix.cpp

@@ -1,209 +0,0 @@
-// Copyright (c) 2023 Oleg Kalachev <okalachev@gmail.com>
-// Repository: https://github.com/okalachev/flix
-
-// Gazebo plugin for running Arduino code and simulating the drone
-
-#include <functional>
-#include <cmath>
-#include <gazebo/gazebo.hh>
-#include <gazebo/physics/physics.hh>
-#include <gazebo/rendering/rendering.hh>
-#include <gazebo/common/common.hh>
-#include <gazebo/sensors/sensors.hh>
-#include <gazebo/msgs/msgs.hh>
-#include <ignition/math/Vector3.hh>
-#include <ignition/math/Pose3.hh>
-#include <ignition/math/Quaternion.hh>
-#include <iostream>
-#include <fstream>
-
-#include "Arduino.h"
-#include "flix.h"
-#include "util.ino"
-#include "joystick.h"
-#include "time.ino"
-#include "estimate.ino"
-#include "control.ino"
-#include "log.ino"
-#include "cli.ino"
-#include "lpf.h"
-
-using ignition::math::Vector3d;
-using ignition::math::Pose3d;
-using namespace gazebo;
-using namespace std;
-
-Pose3d flu2frd(const Pose3d& p)
-{
-	return ignition::math::Pose3d(p.Pos().X(), -p.Pos().Y(), -p.Pos().Z(),
-	                              p.Rot().W(), p.Rot().X(), -p.Rot().Y(), -p.Rot().Z());
-}
-
-Vector flu2frd(const Vector3d& v)
-{
-	return Vector(v.X(), -v.Y(), -v.Z());
-}
-
-class ModelFlix : public ModelPlugin
-{
-private:
-	physics::ModelPtr model, estimateModel;
-	physics::LinkPtr body;
-	sensors::ImuSensorPtr imu;
-	event::ConnectionPtr updateConnection, resetConnection;
-	transport::NodePtr nodeHandle;
-	transport::PublisherPtr motorPub[4];
-	LowPassFilter<Vector> accFilter = LowPassFilter<Vector>(0.1);
-
-public:
-	void Load(physics::ModelPtr _parent, sdf::ElementPtr /*_sdf*/)
-	{
-		this->model = _parent;
-		this->body = this->model->GetLink("body");
-
-		this->imu = std::dynamic_pointer_cast<sensors::ImuSensor>(sensors::get_sensor(model->GetScopedName(true) + "::body::imu")); // default::flix::body::imu
-		if (imu == nullptr) {
-			gzerr << "IMU sensor not found" << std::endl;
-			return;
-		}
-
-		this->estimateModel = model->GetWorld()->ModelByName("flix_estimate");
-
-		this->updateConnection = event::Events::ConnectWorldUpdateBegin(
-			std::bind(&ModelFlix::OnUpdate, this));
-
-		this->resetConnection = event::Events::ConnectWorldReset(
-			std::bind(&ModelFlix::OnReset, this));
-
-		initNode();
-
-		Serial.begin(0);
-
-		gzmsg << "Flix plugin loaded" << endl;
-	}
-
-public:
-	void OnReset()
-	{
-		attitude = Quaternion();
-		gzmsg << "Flix plugin reset" << endl;
-	}
-
-	void OnUpdate()
-	{
-		__micros = model->GetWorld()->SimTime().Double() * 1000000;
-		step();
-
-		// read imu
-		rates = flu2frd(imu->AngularVelocity());
-		acc = this->accFilter.update(flu2frd(imu->LinearAcceleration()));
-
-		// read rc
-		joystickGet();
-		controls[RC_CHANNEL_MODE] = 1; // 0 acro, 1 stab
-		controls[RC_CHANNEL_AUX] = 1; // armed
-
-		estimate();
-
-		// correct yaw to the actual yaw
-		attitude.setYaw(-this->model->WorldPose().Yaw());
-
-		control();
-		parseInput();
-
-		applyMotorsThrust();
-		updateEstimatePose();
-		publishTopics();
-		logData();
-	}
-
-	void applyMotorsThrust()
-	{
-		// thrusts
-		const double d = 0.035355;
-		const double maxThrust = 0.03 * ONE_G; // 30 g, https://www.youtube.com/watch?v=VtKI4Pjx8Sk
-		// 65 mm prop ~40 g
-
-		const float scale0 = 1.0, scale1 = 1.1, scale2 = 0.9, scale3 = 1.05;
-		const float minThrustRel = 0;
-
-		// apply min thrust
-		float mfl = mapff(motors[MOTOR_FRONT_LEFT], 0, 1, minThrustRel, 1);
-		float mfr = mapff(motors[MOTOR_FRONT_RIGHT], 0, 1, minThrustRel, 1);
-		float mrl = mapff(motors[MOTOR_REAR_LEFT], 0, 1, minThrustRel, 1);
-		float mrr = mapff(motors[MOTOR_REAR_RIGHT], 0, 1, minThrustRel, 1);
-
-		if (motors[MOTOR_FRONT_LEFT] < 0.001) mfl = 0;
-		if (motors[MOTOR_FRONT_RIGHT] < 0.001) mfr = 0;
-		if (motors[MOTOR_REAR_LEFT] < 0.001) mrl = 0;
-		if (motors[MOTOR_REAR_RIGHT] < 0.001) mrr = 0;
-
-		// TODO: min_thrust
-
-		body->AddLinkForce(Vector3d(0.0, 0.0, scale0 * maxThrust * abs(mfl)), Vector3d(d, d, 0.0));
-		body->AddLinkForce(Vector3d(0.0, 0.0, scale1 * maxThrust * abs(mfr)), Vector3d(d, -d, 0.0));
-		body->AddLinkForce(Vector3d(0.0, 0.0, scale2 * maxThrust * abs(mrl)), Vector3d(-d, d, 0.0));
-		body->AddLinkForce(Vector3d(0.0, 0.0, scale3 * maxThrust * abs(mrr)), Vector3d(-d, -d, 0.0));
-
-		// TODO: indicate if > 1
-
-		// torque
-		const double maxTorque = 0.0023614413; // 24.08 g*cm
-		int direction = 1;
-		// z is counter clockwise, normal rotation direction is minus
-		body->AddRelativeTorque(Vector3d(0.0, 0.0, direction * scale0 * maxTorque * motors[MOTOR_FRONT_LEFT]));
-		body->AddRelativeTorque(Vector3d(0.0, 0.0, direction * scale1 * -maxTorque * motors[MOTOR_FRONT_RIGHT]));
-		body->AddRelativeTorque(Vector3d(0.0, 0.0, direction * scale2 * -maxTorque * motors[MOTOR_REAR_LEFT]));
-		body->AddRelativeTorque(Vector3d(0.0, 0.0, direction * scale3 * maxTorque * motors[MOTOR_REAR_RIGHT]));
-	}
-
-	void updateEstimatePose() {
-		if (estimateModel == nullptr) {
-			return;
-		}
-		if (!attitude.finite()) {
-			// gzerr << "attitude is nan" << std::endl;
-			return;
-		}
-		Pose3d pose(
-			model->WorldPose().Pos().X(), model->WorldPose().Pos().Y(), model->WorldPose().Pos().Z(),
-			attitude.w, attitude.x, -attitude.y, -attitude.z // frd to flu
-		);
-		// std::cout << pose.Pos().X() << " " << pose.Pos().Y() << " " << pose.Pos().Z() <<
-		// 	" " << pose.Rot().W() << " " << pose.Rot().X() << " " << pose.Rot().Y() << " " << pose.Rot().Z() << std::endl;
-
-		// calculate attitude estimation error
-
-		Quaternion groundtruthAttitude(estimateModel->WorldPose().Rot().W(), estimateModel->WorldPose().Rot().X(), -estimateModel->WorldPose().Rot().Y(), -estimateModel->WorldPose().Rot().Z());
-		float angle = Vector::angleBetweenVectors(attitude.rotate(Vector(0, 0, -1)), groundtruthAttitude.rotate(Vector(0, 0, -1)));
-		if (angle < 0.3) {
-			//gzwarn << "att err: " << angle << endl;
-			// TODO: warning
-			// position under the floor to make it invisible
-			pose.SetZ(-5);
-		}
-
-		estimateModel->SetWorldPose(pose);
-
-	}
-
-	void initNode() {
-		nodeHandle = transport::NodePtr(new transport::Node());
-		nodeHandle->Init();
-		string ns = "~/" + model->GetName();
-		motorPub[0] = nodeHandle->Advertise<msgs::Int>(ns + "/motor0");
-		motorPub[1] = nodeHandle->Advertise<msgs::Int>(ns + "/motor1");
-		motorPub[2] = nodeHandle->Advertise<msgs::Int>(ns + "/motor2");
-		motorPub[3] = nodeHandle->Advertise<msgs::Int>(ns + "/motor3");
-	}
-
-	void publishTopics() {
-		for (int i = 0; i < 4; i++) {
-			msgs::Int msg;
-			msg.set_data(static_cast<int>(std::round(motors[i] * 1000)));
-			motorPub[i]->Publish(msg);
-		}
-	}
-};
-
-GZ_REGISTER_MODEL_PLUGIN(ModelFlix)

gazebo/flix.h

@@ -8,29 +8,35 @@
 #include "vector.h"
 #include "quaternion.h"
 #include "Arduino.h"
+#include "wifi.h"
 
-#define RC_CHANNELS 6
+#define RC_CHANNELS 16
 
 #define MOTOR_REAR_LEFT 0
 #define MOTOR_FRONT_LEFT 3
 #define MOTOR_FRONT_RIGHT 2
 #define MOTOR_REAR_RIGHT 1
 
+#define WIFI_ENABLED 1
+
+#define ONE_G 9.80665
+
 float t = NAN;
 float dt;
-float loopFreq;
+float loopRate;
 float motors[4];
-int16_t channels[16]; // raw rc channels WARNING: unsigned on hardware
+int16_t channels[16]; // raw rc channels
 float controls[RC_CHANNELS];
+float controlsTime;
 Vector acc;
+Vector gyro;
 Vector rates;
 Quaternion attitude;
 
 // declarations
-void computeLoopFreq();
+void computeLoopRate();
 void applyGyro();
 void applyAcc();
-void signalizeHorizontality();
 void control();
 void interpretRC();
 void controlAttitude();
@@ -39,11 +45,23 @@ void controlTorque();
 void showTable();
 bool motorsActive();
 void cliTestMotor(uint8_t n);
+String stringToken(char* str, const char* delim);
+void normalizeRC();
+void printRCCal();
+void processMavlink();
+void sendMavlink();
+void sendMessage(const void *msg);
+void receiveMavlink();
+void handleMavlink(const void *_msg);
+void failsafe();
+void descend();
+inline Quaternion FLU2FRD(const Quaternion &q);
 
 // mocks
 void setLED(bool on) {};
 void calibrateGyro() { printf("Skip gyro calibrating\n"); };
 void calibrateAccel() { printf("Skip accel calibrating\n"); };
-void fullMotorTest(int n, bool reverse) { printf("Skip full motor test\n"); };
 void sendMotors() {};
 void printIMUCal() { printf("cal: N/A\n"); };
+void printIMUInfo() {};
+Vector accBias, gyroBias, accScale(1, 1, 1);

gazebo/flix.world

@@ -9,7 +9,7 @@
 		</scene>
 		<gui>
 			<camera name="user_camera">
-				<pose>-2 -0.3 1.5 0 0.5 0.1</pose>
+				<pose>-2.3 0 1.1 0 0.3 0</pose>
 			</camera>
 		</gui>
 		<physics type="ode">
@@ -23,20 +23,7 @@
 		</include>
 		<include>
 			<uri>model://flix</uri>
-			<pose>0 0 0.2 0 0 0</pose>
+			<pose>0 0 0.3 0 0 0</pose>
 		</include>
-		<model name="flix_estimate">
-			<static>true</static>
-			<link name="estimate">
-				<visual name="estimate">
-					<pose>0 0 0 0 0 1.57</pose>
-					<geometry>
-						<box>
-							<size>0.125711 0.125711 0.022</size>
-						</box>
-					</geometry>
-				</visual>
-			</link>
-		</model>
 	</world>
 </sdf>

gazebo/joystick.h

@@ -7,64 +7,38 @@
 #include <gazebo/gazebo.hh>
 #include <iostream>
 
-using namespace std;
-
-static const int16_t channelNeutralMin[] = {-1290,	-258,	-26833,	0,	0, 0};
-static const int16_t channelNeutralMax[] = {-1032,	-258,	-27348,	3353,	0, 0};
-
-static const int16_t channelMax[] =        {27090,	27090,	27090,	27090, 0, 0};
-
 #define RC_CHANNEL_ROLL 0
 #define RC_CHANNEL_PITCH 1
 #define RC_CHANNEL_THROTTLE 2
 #define RC_CHANNEL_YAW 3
-#define RC_CHANNEL_AUX 4
-#define RC_CHANNEL_MODE 5
-
-static SDL_Joystick *joystick;
+#define RC_CHANNEL_ARMED 5
+#define RC_CHANNEL_MODE 4
 
+SDL_Joystick *joystick;
 bool joystickInitialized = false, warnShown = false;
 
-void normalizeRC();
-
-void joystickInit()
-{
+void joystickInit() {
 	SDL_Init(SDL_INIT_JOYSTICK);
 	joystick = SDL_JoystickOpen(0);
 	if (joystick != NULL) {
 		joystickInitialized = true;
-		gzmsg << "Joystick initialized: " << SDL_JoystickNameForIndex(0) << endl;
+		gzmsg << "Joystick initialized: " << SDL_JoystickNameForIndex(0) << std::endl;
 	} else if (!warnShown) {
-		gzwarn << "Joystick not found, begin waiting for joystick..." << endl;
+		gzwarn << "Joystick not found, begin waiting for joystick..." << std::endl;
 		warnShown = true;
 	}
 }
 
-void joystickGet()
-{
+bool joystickGet(int16_t ch[16]) {
 	if (!joystickInitialized) {
 		joystickInit();
-		return;
+		return false;
 	}
 
 	SDL_JoystickUpdate();
 
-	for (uint8_t i = 0; i < 4; i++) {
-		channels[i] = SDL_JoystickGetAxis(joystick, i);
+	for (uint8_t i = 0; i < sizeof(channels) / sizeof(channels[0]); i++) {
+		ch[i] = SDL_JoystickGetAxis(joystick, i);
 	}
-	channels[RC_CHANNEL_MODE] = SDL_JoystickGetButton(joystick, 0) ? 1 : 0;
-	controls[RC_CHANNEL_MODE] = channels[RC_CHANNEL_MODE];
-
-	normalizeRC();
-}
-
-void normalizeRC() {
-	for (uint8_t i = 0; i < 4; i++) {
-		if (channels[i] >= channelNeutralMin[i] && channels[i] <= channelNeutralMax[i]) {
-			controls[i] = 0;
-		} else {
-			controls[i] = mapf(channels[i], (channelNeutralMin[i] + channelNeutralMax[i]) / 2, channelMax[i], 0, 1);
-		}
-	}
-	controls[RC_CHANNEL_THROTTLE] = constrain(controls[RC_CHANNEL_THROTTLE], 0, 1);
+	return true;
 }

gazebo/models/flix/flix.sdf

@@ -13,15 +13,10 @@
 			<collision name="collision">
 				<geometry>
 					<box>
-						<size>0.125711 0.125711 0.022</size>
+						<size>0.095 0.095 0.0276</size>
 					</box>
 				</geometry>
 			</collision>
-			<visual name="body">
-				<geometry>
-					<mesh><uri>model://flix/flix.dae</uri></mesh>
-				</geometry>
-			</visual>
 			<sensor name="imu" type="imu">
 				<always_on>1</always_on>
 				<visualize>1</visualize>
@@ -63,6 +58,37 @@
 					</linear_acceleration>
 				</imu>
 			</sensor>
+			<visual name="body">
+				<geometry>
+					<mesh><uri>model://flix/flix.stl</uri></mesh>
+				</geometry>
+				<material>
+					<ambient>0.5 0.5 0.6 1</ambient>
+					<diffuse>0.5 0.5 0.6 1</diffuse>
+					<specular>0 0 0 1</specular>
+					<emissive>0 0 0 1</emissive>
+				</material>
+			</visual>
+			<visual name="prop0"><!-- rear left -->
+				<geometry><cylinder><radius>0.0275</radius><length>0</length></cylinder></geometry>
+				<pose>-0.04243 0.04243 0.0142 0 0 0</pose>
+				<material><ambient>0.8 0.3 0.3 0.5</ambient><diffuse>0.8 0.3 0.3 0.5</diffuse></material>
+			</visual>
+			<visual name="prop1"><!-- rear right -->
+				<geometry><cylinder><radius>0.0275</radius><length>0</length></cylinder></geometry>
+				<pose>-0.04243 -0.04243 0.0142 0 0 0</pose>
+				<material><ambient>0.8 0.3 0.3 0.5</ambient><diffuse>0.8 0.3 0.3 0.5</diffuse></material>
+			</visual>
+			<visual name="prop2"><!-- front right -->
+				<geometry><cylinder><radius>0.0275</radius><length>0</length></cylinder></geometry>
+				<pose>0.04243 -0.04243 0.0142 0 0 0</pose>
+				<material><ambient>1 1 1 0.5</ambient><diffuse>1 1 1 0.5</diffuse></material>
+			</visual>
+			<visual name="prop3"><!-- front left -->
+				<geometry><cylinder><radius>0.0275</radius><length>0</length></cylinder></geometry>
+				<pose>0.04243 0.04243 0.0142 0 0 0</pose>
+				<material><ambient>1 1 1 0.5</ambient><diffuse>1 1 1 0.5</diffuse></material>
+			</visual>
 		</link>
 		<plugin name="flix" filename="libflix.so"/>
 	</model>

gazebo/simulator.cpp

@@ -0,0 +1,137 @@
+// Copyright (c) 2023 Oleg Kalachev <okalachev@gmail.com>
+// Repository: https://github.com/okalachev/flix
+
+// Gazebo plugin for running Arduino code and simulating the drone
+
+#include <functional>
+#include <cmath>
+#include <gazebo/gazebo.hh>
+#include <gazebo/physics/physics.hh>
+#include <gazebo/common/common.hh>
+#include <gazebo/sensors/sensors.hh>
+#include <gazebo/msgs/msgs.hh>
+#include <ignition/math/Vector3.hh>
+#include <ignition/math/Pose3.hh>
+#include <iostream>
+#include <fstream>
+
+#include "Arduino.h"
+#include "flix.h"
+#include "util.ino"
+#include "rc.ino"
+#include "time.ino"
+#include "estimate.ino"
+#include "control.ino"
+#include "log.ino"
+#include "parameters.ino"
+#include "cli.ino"
+#include "mavlink.ino"
+#include "failsafe.ino"
+#include "lpf.h"
+
+using ignition::math::Vector3d;
+using namespace gazebo;
+using namespace std;
+
+class ModelFlix : public ModelPlugin {
+private:
+	physics::ModelPtr model;
+	physics::LinkPtr body;
+	sensors::ImuSensorPtr imu;
+	event::ConnectionPtr updateConnection, resetConnection;
+	transport::NodePtr nodeHandle;
+	transport::PublisherPtr motorPub[4];
+	LowPassFilter<Vector> accFilter = LowPassFilter<Vector>(0.1);
+
+public:
+	void Load(physics::ModelPtr _parent, sdf::ElementPtr /*_sdf*/) {
+		this->model = _parent;
+		this->body = this->model->GetLink("body");
+		this->imu = dynamic_pointer_cast<sensors::ImuSensor>(sensors::get_sensor(model->GetScopedName(true) + "::body::imu")); // default::flix::body::imu
+		this->updateConnection = event::Events::ConnectWorldUpdateBegin(std::bind(&ModelFlix::OnUpdate, this));
+		this->resetConnection = event::Events::ConnectWorldReset(std::bind(&ModelFlix::OnReset, this));
+		initNode();
+		Serial.begin(0);
+		setupParameters();
+		gzmsg << "Flix plugin loaded" << endl;
+	}
+
+	void OnReset() {
+		attitude = Quaternion(); // reset estimated attitude
+		__resetTime += __micros;
+		gzmsg << "Flix plugin reset" << endl;
+	}
+
+	void OnUpdate() {
+		__micros = model->GetWorld()->SimTime().Double() * 1000000;
+		step();
+
+		// read virtual imu
+		gyro = Vector(imu->AngularVelocity().X(), imu->AngularVelocity().Y(), imu->AngularVelocity().Z());
+		acc = this->accFilter.update(Vector(imu->LinearAcceleration().X(), imu->LinearAcceleration().Y(), imu->LinearAcceleration().Z()));
+
+		// read rc
+		readRC();
+		controls[RC_CHANNEL_MODE] = 1; // 0 acro, 1 stab
+		controls[RC_CHANNEL_ARMED] = 1; // armed
+
+		estimate();
+
+		// correct yaw to the actual yaw
+		attitude.setYaw(this->model->WorldPose().Yaw());
+
+		control();
+		parseInput();
+		processMavlink();
+
+		applyMotorForces();
+		publishTopics();
+		logData();
+		flushParameters();
+	}
+
+	void applyMotorForces() {
+		// thrusts
+		const double dist = 0.035355; // motors shift from the center, m
+		const double maxThrust = 0.03 * ONE_G; // ~30 g, https://youtu.be/VtKI4Pjx8Sk?&t=78
+
+		const float scale0 = 1.0, scale1 = 1.1, scale2 = 0.9, scale3 = 1.05; // imitating motors asymmetry
+		float mfl = scale0 * maxThrust * motors[MOTOR_FRONT_LEFT];
+		float mfr = scale1 * maxThrust * motors[MOTOR_FRONT_RIGHT];
+		float mrl = scale2 * maxThrust * motors[MOTOR_REAR_LEFT];
+		float mrr = scale3 * maxThrust * motors[MOTOR_REAR_RIGHT];
+
+		body->AddLinkForce(Vector3d(0.0, 0.0, mfl), Vector3d(dist, dist, 0.0));
+		body->AddLinkForce(Vector3d(0.0, 0.0, mfr), Vector3d(dist, -dist, 0.0));
+		body->AddLinkForce(Vector3d(0.0, 0.0, mrl), Vector3d(-dist, dist, 0.0));
+		body->AddLinkForce(Vector3d(0.0, 0.0, mrr), Vector3d(-dist, -dist, 0.0));
+
+		// torque
+		const double maxTorque = 0.0024 * ONE_G; // ~24 g*cm
+		body->AddRelativeTorque(Vector3d(0.0, 0.0, scale0 * maxTorque * motors[MOTOR_FRONT_LEFT]));
+		body->AddRelativeTorque(Vector3d(0.0, 0.0, scale1 * -maxTorque * motors[MOTOR_FRONT_RIGHT]));
+		body->AddRelativeTorque(Vector3d(0.0, 0.0, scale2 * -maxTorque * motors[MOTOR_REAR_LEFT]));
+		body->AddRelativeTorque(Vector3d(0.0, 0.0, scale3 * maxTorque * motors[MOTOR_REAR_RIGHT]));
+	}
+
+	void initNode() {
+		nodeHandle = transport::NodePtr(new transport::Node());
+		nodeHandle->Init();
+		string ns = "~/" + model->GetName();
+		// create motors output topics for debugging and plotting
+		motorPub[0] = nodeHandle->Advertise<msgs::Int>(ns + "/motor0");
+		motorPub[1] = nodeHandle->Advertise<msgs::Int>(ns + "/motor1");
+		motorPub[2] = nodeHandle->Advertise<msgs::Int>(ns + "/motor2");
+		motorPub[3] = nodeHandle->Advertise<msgs::Int>(ns + "/motor3");
+	}
+
+	void publishTopics() {
+		for (int i = 0; i < 4; i++) {
+			msgs::Int msg;
+			msg.set_data(static_cast<int>(round(motors[i] * 1000)));
+			motorPub[i]->Publish(msg);
+		}
+	}
+};
+
+GZ_REGISTER_MODEL_PLUGIN(ModelFlix)

gazebo/soc/rtc_cntl_reg.h

@@ -0,0 +1 @@
+// Dummy file to make it possible to compile simulator with util.ino