Fix rates, acc and gyro coordinate frame in mavlink

All of them should be in frd.
Get rid of fluToFrd function - there is no big need for it.

.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

@@ -7,58 +7,77 @@ 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: Build firmware without Wi-Fi
+      run: sed -i 's/^#define WIFI_ENABLED 1$/#define WIFI_ENABLED 0/' flix/flix.ino && make
+    - name: Check c_cpp_properties.json
+      run: tools/check_c_cpp_properties.py
 
   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
+    runs-on: ubuntu-22.04
     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
       run: sudo apt-get install libsdl2-dev
     - name: Build simulator
       run: make build_simulator
-    - uses: actions/upload-artifact@v3
+    - uses: actions/upload-artifact@v4
       with:
         name: gazebo-plugin-binary
         path: gazebo/build/*.so
         retention-days: 1
 
-  # build_simulator_macos:
-  #   runs-on: macos-latest
-  #   steps:
-  #   - uses: actions/checkout@v3
-  #   - name: Install Gazebo
-  #     run: brew tap osrf/simulation && brew install gazebo11
-  #   - name: Install SDL2
-  #     run: brew install sdl2
-  #   - name: Build simulator
-  #     run: make build_simulator
+#  build_simulator_macos:
+#    runs-on: macos-latest
+#    steps:
+#    - 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 update && brew tap osrf/simulation && brew install gazebo11
+#    - name: Install SDL2
+#      run: brew install sdl2
+#    - name: Build simulator
+#      run: make build_simulator

.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

.vscode/c_cpp_properties.json

@@ -0,0 +1,144 @@
+{
+	"configurations": [
+		{
+			"name": "Linux",
+			"includePath": [
+				"${workspaceFolder}/flix",
+				"${workspaceFolder}/gazebo",
+				"~/.arduino15/packages/esp32/hardware/esp32/3.2.0/cores/esp32",
+				"~/.arduino15/packages/esp32/hardware/esp32/3.2.0/libraries/**",
+				"~/.arduino15/packages/esp32/hardware/esp32/3.2.0/variants/d1_mini32",
+				"~/.arduino15/packages/esp32/tools/esp32-arduino-libs/idf-release_v5.4-2f7dcd86-v1/esp32/**",
+				"~/.arduino15/packages/esp32/tools/esp32-arduino-libs/idf-release_v5.4-2f7dcd86-v1/esp32/dio_qspi/include",
+				"~/Arduino/libraries/**",
+				"/usr/include/**"
+			],
+			"forcedInclude": [
+				"${workspaceFolder}/.vscode/intellisense.h",
+				"~/.arduino15/packages/esp32/hardware/esp32/3.2.0/cores/esp32/Arduino.h",
+				"~/.arduino15/packages/esp32/hardware/esp32/3.2.0/variants/d1_mini32/pins_arduino.h",
+				"${workspaceFolder}/flix/cli.ino",
+				"${workspaceFolder}/flix/control.ino",
+				"${workspaceFolder}/flix/estimate.ino",
+				"${workspaceFolder}/flix/flix.ino",
+				"${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",
+				"${workspaceFolder}/flix/wifi.ino"
+			],
+			"compilerPath": "~/.arduino15/packages/esp32/tools/esp-x32/2411/bin/xtensa-esp32-elf-g++",
+			"cStandard": "c11",
+			"cppStandard": "c++17",
+			"defines": [
+				"F_CPU=240000000L",
+				"ARDUINO=10607",
+				"ARDUINO_D1_MINI32",
+				"ARDUINO_ARCH_ESP32",
+				"ARDUINO_BOARD=D1_MINI32",
+				"ARDUINO_VARIANT=d1_mini32",
+				"ARDUINO_PARTITION_default",
+				"ESP32",
+				"CORE_DEBUG_LEVEL=0",
+				"ARDUINO_USB_CDC_ON_BOOT="
+			]
+		},
+		{
+			"name": "Mac",
+			"includePath": [
+				"${workspaceFolder}/flix",
+				// "${workspaceFolder}/gazebo",
+				"~/Library/Arduino15/packages/esp32/hardware/esp32/3.2.0/cores/esp32",
+				"~/Library/Arduino15/packages/esp32/hardware/esp32/3.2.0/libraries/**",
+				"~/Library/Arduino15/packages/esp32/hardware/esp32/3.2.0/variants/d1_mini32",
+				"~/Library/Arduino15/packages/esp32/tools/esp32-arduino-libs/idf-release_v5.4-2f7dcd86-v1/esp32/include/**",
+				"~/Library/Arduino15/packages/esp32/tools/esp32-arduino-libs/idf-release_v5.4-2f7dcd86-v1/esp32/dio_qspi/include",
+				"~/Documents/Arduino/libraries/**",
+				"/opt/homebrew/include/**"
+			],
+			"forcedInclude": [
+				"${workspaceFolder}/.vscode/intellisense.h",
+				"~/Library/Arduino15/packages/esp32/hardware/esp32/3.2.0/cores/esp32/Arduino.h",
+				"~/Library/Arduino15/packages/esp32/hardware/esp32/3.2.0/variants/d1_mini32/pins_arduino.h",
+				"${workspaceFolder}/flix/flix.ino",
+				"${workspaceFolder}/flix/cli.ino",
+				"${workspaceFolder}/flix/control.ino",
+				"${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/wifi.ino"
+			],
+			"compilerPath": "~/Library/Arduino15/packages/esp32/tools/esp-x32/2411/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/esp32/3.2.0/cores/esp32",
+				"~/AppData/Local/Arduino15/packages/esp32/hardware/esp32/3.2.0/libraries/**",
+				"~/AppData/Local/Arduino15/packages/esp32/hardware/esp32/3.2.0/variants/d1_mini32",
+				"~/AppData/Local/Arduino15/packages/esp32/tools/esp32-arduino-libs/idf-release_v5.4-2f7dcd86-v1/esp32/**",
+				"~/AppData/Local/Arduino15/packages/esp32/tools/esp32-arduino-libs/idf-release_v5.4-2f7dcd86-v1/esp32/dio_qspi/include",
+				"~/Documents/Arduino/libraries/**"
+			],
+			"forcedInclude": [
+				"${workspaceFolder}/.vscode/intellisense.h",
+				"~/AppData/Local/Arduino15/packages/esp32/hardware/esp32/3.2.0/cores/esp32/Arduino.h",
+				"~/AppData/Local/Arduino15/packages/esp32/hardware/esp32/3.2.0/variants/d1_mini32/pins_arduino.h",
+				"${workspaceFolder}/flix/cli.ino",
+				"${workspaceFolder}/flix/control.ino",
+				"${workspaceFolder}/flix/estimate.ino",
+				"${workspaceFolder}/flix/flix.ino",
+				"${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/wifi.ino"
+			],
+			"compilerPath": "~/AppData/Local/Arduino15/packages/esp32/tools/esp-x32/2411/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 +1,9 @@
+{
+	// See https://go.microsoft.com/fwlink/?LinkId=827846 to learn about workspace recommendations.
+	"recommendations": [
+		"ms-vscode.cpptools",
+		"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@3.2.0 --config-file arduino-cli.yaml
+	arduino-cli lib update-index
+	arduino-cli lib install "FlixPeriph"
+	arduino-cli lib install "MAVLink"@2.0.16
 	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 +1,7 @@
-# flix
+# Flix
 
-**flix** (*flight + X*) — making an open source ESP32-based quadcopter from scratch.
+Minimal **Flix** quadcopter firmware implementation for the [book](https://quadcopter.dev).
 
-<img src="docs/img/flix.jpg" width=500>
+See the full code and documentation in the main branch: https://github.com/okalachev/flix.
 
-## Features
-
-* Simple and clear Arduino based source code.
-* Acro and Stabilized flight using remote control.
-* Precise simulation using Gazebo.
-* In-RAM logging.
-* 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\**.
-* [Building and running instructions](docs/build.md).
-
-*\* — planned.*
-
-## It actually flies
-
-<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.
-
-## Simulation
-
-Simulation in Gazebo using a plugin that runs original Arduino code is implemented:
-
-<img src="docs/img/simulator.png" width=500>
-
-## Schematics
-
-<img src="docs/img/schematics.svg" width=800>
-
-## Version 0
-
-### Components
-
-|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||
+<img src="docs/img/flix1.jpg" width=500 alt="Flix quadcopter">

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/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);
+#11=SHAPE_REPRESENTATION_RELATIONSHIP('SRR','None',#132,#12);
+#12=ADVANCED_BREP_SHAPE_REPRESENTATION('',(#14),#124);
+#13=STYLED_ITEM('',(#141),#14);
+#14=MANIFOLD_SOLID_BREP('Body1',#65);
+#15=FACE_BOUND('',#26,.T.);
+#16=FACE_BOUND('',#28,.T.);
+#17=PLANE('',#85);
+#18=PLANE('',#86);
+#19=FACE_OUTER_BOUND('',#23,.T.);
+#20=FACE_OUTER_BOUND('',#24,.T.);
+#21=FACE_OUTER_BOUND('',#25,.T.);
+#22=FACE_OUTER_BOUND('',#27,.T.);
+#23=EDGE_LOOP('',(#47,#48,#49,#50));
+#24=EDGE_LOOP('',(#51,#52,#53,#54));
+#25=EDGE_LOOP('',(#55));
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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
 
-1. Install Gazebo 11:
+The latest version of Ubuntu supported by Gazebo 11 simulator is 22.04. If you have a newer version, consider using a virtual machine.
+
+1. Install Arduino CLI:
+
+   ```bash
+   curl -fsSL https://raw.githubusercontent.com/arduino/arduino-cli/master/install.sh | BINDIR=~/.local/bin sh
+   ```
+
+2. Install Gazebo 11:
 
    ```bash
    curl -sSL http://get.gazebosim.org | sh
@@ -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 +58,63 @@ 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 and stop the simulation.
+4. Copy the calibration results to the source code (`gazebo/joystick.h`).
+5. Run the simulation again.
+6. 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. Windows users might need to install [USB to UART bridge driver from Silicon Labs](https://www.silabs.com/developers/usb-to-uart-bridge-vcp-drivers).
+3. Install ESP32 core, version 3.2.0. See the [official Espressif's instructions](https://docs.espressif.com/projects/arduino-esp32/en/latest/installing.html#installing-using-arduino-ide) on installing ESP32 Core in Arduino IDE.
+4. Install the following libraries using [Library Manager](https://docs.arduino.cc/software/ide-v2/tutorials/ide-v2-installing-a-library):
+   * `FlixPeriph`, the latest version.
+   * `MAVLink`, version 2.0.16.
+5. Clone the project using git or [download the source code as a ZIP archive](https://codeload.github.com/okalachev/flix/zip/refs/heads/master).
+6. Open the downloaded Arduino sketch `flix/flix.ino` in Arduino IDE.
+7. Connect your ESP32 board to the computer and choose correct board type in Arduino IDE (*WEMOS D1 MINI ESP32* for ESP32 Mini) and the port.
+8. [Build and upload](https://docs.arduino.cc/software/ide-v2/tutorials/getting-started/ide-v2-uploading-a-sketch) the firmware using Arduino IDE.
 
 ### Command line (Windows, Linux, macOS)
 
@@ -84,3 +139,37 @@ 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.
+3. Copy calibration results to the source code (`flix/imu.ino`).
+
+#### 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.
+3. Copy calibration results to the source code (`flix/rc.ino`).
+
+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.
+* `controlRoll`, `controlPitch`, ... *(float[])* — pilot's control inputs, range [-1, 1].
+* `motors` *(float[])* — motor outputs, normalized to [0, 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).

docs/img/dataflow.svg

@@ -0,0 +1,330 @@
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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.

flix/cli.ino

@@ -6,8 +6,9 @@
 #include "pid.h"
 #include "vector.h"
 
-extern PID rollRatePID, pitchRatePID, yawRatePID, rollPID, pitchPID;
-extern LowPassFilter<Vector> ratesFilter;
+extern const int MOTOR_REAR_LEFT, MOTOR_REAR_RIGHT, MOTOR_FRONT_RIGHT, MOTOR_FRONT_LEFT;
+extern float loopRate;
+extern uint16_t channels[16];
 
 const char* motd =
 "\nWelcome to\n"
@@ -19,151 +20,84 @@ const char* motd =
 "|__|     |_______||__| /__/ \\__\\\n\n"
 "Commands:\n\n"
 "help - show help\n"
-"show - show all parameters\n"
-"<name> <value> - set parameter\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"
+"mfr, mfl, mrr, mrl - test motor (remove props)\n"
 "reset - reset drone's state\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(const String& command) {
 	if (command == "help" || command == "motd") {
 		Serial.println(motd);
-	} else if (command == "show") {
-		showTable();
 	} else if (command == "ps") {
-		Vector a = attitude.toEulerZYX();
+		Vector a = attitude.toEuler();
 		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();
+		printIMUCalibration();
+		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",
-			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",
-			controls[RC_CHANNEL_THROTTLE], controls[RC_CHANNEL_YAW], controls[RC_CHANNEL_PITCH],
-			controls[RC_CHANNEL_ROLL], controls[RC_CHANNEL_AUX], controls[RC_CHANNEL_MODE]);
-		Serial.printf("Mode: %s\n", getModeName());
+		Serial.printf("channels: ");
+		for (int i = 0; i < 16; i++) {
+			Serial.printf("%u ", channels[i]);
+		}
+		Serial.printf("\nroll: %g pitch: %g yaw: %g throttle: %g armed: %g mode: %g\n",
+			controlRoll, controlPitch, controlYaw, controlThrottle, controlArmed, controlMode);
+		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",
+		Serial.printf("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") {
 		calibrateAccel();
 	} else if (command == "mfr") {
-		cliTestMotor(MOTOR_FRONT_RIGHT);
+		testMotor(MOTOR_FRONT_RIGHT);
 	} else if (command == "mfl") {
-		cliTestMotor(MOTOR_FRONT_LEFT);
+		testMotor(MOTOR_FRONT_LEFT);
 	} else if (command == "mrr") {
-		cliTestMotor(MOTOR_REAR_RIGHT);
+		testMotor(MOTOR_REAR_RIGHT);
 	} else if (command == "mrl") {
-		cliTestMotor(MOTOR_REAR_LEFT);
-	} else if (command == "fullmot") {
-		fullMotorTest(value.toInt(), false);
+		testMotor(MOTOR_REAR_LEFT);
 	} else if (command == "reset") {
 		attitude = Quaternion();
+	} 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)
-{
-	Serial.printf("Testing motor %d\n", n);
-	motors[n] = 1;
-	sendMotors();
-	delay(5000);
-	motors[n] = 0;
-	sendMotors();
-	Serial.println("Done");
-}
-
-void parseInput()
-{
+void handleInput() {
 	static bool showMotd = true;
-	static String command;
-	static String value;
-	static bool parsingCommand = true;
+	static String input;
 
 	if (showMotd) {
-		Serial.println(motd);
+		Serial.printf("%s\n", motd);
 		showMotd = false;
 	}
 
 	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;
+			doCommand(input);
+			input.clear();
 		} else {
-			(parsingCommand ? command : value) += c;
+			input += c;
 		}
 	}
 }

flix/control.ino

@@ -7,6 +7,7 @@
 #include "quaternion.h"
 #include "pid.h"
 #include "lpf.h"
+#include "util.h"
 
 #define PITCHRATE_P 0.05
 #define PITCHRATE_I 0.2
@@ -27,15 +28,14 @@
 #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(300)
+#define TILT_MAX 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 +46,16 @@ 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()
-{
+extern const int MOTOR_REAR_LEFT, MOTOR_REAR_RIGHT, MOTOR_FRONT_RIGHT, MOTOR_FRONT_LEFT;
+
+void control() {
 	interpretRC();
+	failsafe();
 	if (mode == STAB) {
 		controlAttitude();
 		controlRate();
@@ -68,38 +68,40 @@ void control()
 	}
 }
 
-void interpretRC()
-{
-	if (controls[RC_CHANNEL_MODE] < 0.25) {
-		mode = MANUAL;
-	} else if (controls[RC_CHANNEL_MODE] < 0.75) {
-		mode = ACRO;
+void interpretRC() {
+	armed = controlThrottle >= 0.05 && controlArmed >= 0.5;
+
+
+	// NOTE: put ACRO or MANUAL modes there if you want to use them
+	if (controlMode < 0.25) {
+		mode = STAB;
+	} else if (controlMode < 0.75) {
+		mode = STAB;
 	} else {
 		mode = STAB;
 	}
 
-	armed = controls[RC_CHANNEL_THROTTLE] >= 0.05 && controls[RC_CHANNEL_AUX] >= 0.5;
-	thrustTarget = controls[RC_CHANNEL_THROTTLE];
+	thrustTarget = controlThrottle;
 
 	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.x = controlRoll * ROLLRATE_MAX;
+		ratesTarget.y = controlPitch * PITCHRATE_MAX;
+		ratesTarget.z = -controlYaw * YAWRATE_MAX; // positive yaw stick means clockwise rotation in FLU
 
 	} else if (mode == STAB) {
-		yawMode = controls[RC_CHANNEL_YAW] == 0 ? YAW : YAW_RATE;
+		yawMode = controlYaw == 0 ? YAW : YAW_RATE;
 
-		attitudeTarget = Quaternion::fromEulerZYX(
-			controls[RC_CHANNEL_ROLL] * MAX_TILT,
-			-controls[RC_CHANNEL_PITCH] * MAX_TILT,
-			attitudeTarget.getYaw());
-		ratesTarget.z = controls[RC_CHANNEL_YAW] * YAWRATE_MAX;
+		attitudeTarget = Quaternion::fromEuler(Vector(
+			controlRoll * TILT_MAX,
+			controlPitch * TILT_MAX,
+			attitudeTarget.getYaw()));
+		ratesTarget.z = -controlYaw * 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(controlRoll, controlPitch, -controlYaw) * 0.01;
 	}
 
 	if (yawMode == YAW_RATE || !motorsActive()) {
@@ -108,8 +110,7 @@ void interpretRC()
 	}
 }
 
-void controlAttitude()
-{
+void controlAttitude() {
 	if (!armed) {
 		rollPID.reset();
 		pitchPID.reset();
@@ -117,22 +118,22 @@ void controlAttitude()
 		return;
 	}
 
-	const Vector up(0, 0, -1);
-	Vector upActual = attitude.rotate(up);
-	Vector upTarget = attitudeTarget.rotate(up);
+	const Vector up(0, 0, 1);
+	Vector upActual = Quaternion::rotateVector(up, attitude);
+	Vector upTarget = Quaternion::rotateVector(up, attitudeTarget);
 
-	Vector error = Vector::angularRatesBetweenVectors(upTarget, upActual);
+	Vector error = Vector::rotationVectorBetween(upTarget, upActual);
 
 	ratesTarget.x = rollPID.update(error.x, dt);
 	ratesTarget.y = pitchPID.update(error.y, dt);
 
 	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 +141,24 @@ 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 +166,12 @@ void controlTorque()
 	motors[3] = constrain(motors[3], 0, 1);
 }
 
-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

@@ -5,28 +5,28 @@
 
 #include "quaternion.h"
 #include "vector.h"
+#include "lpf.h"
+#include "util.h"
 
-#define ONE_G 9.807f
-#define ACC_MIN 0.9f
-#define ACC_MAX 1.1f
-#define WEIGHT_ACC 0.5f
+#define WEIGHT_ACC 0.003
+#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
-	attitude *= Quaternion::fromAngularRates(rates * dt);
-	attitude.normalize();
+void applyGyro() {
+	// filter gyro to get angular rates
+	rates = ratesFilter.update(gyro);
+
+	// apply rates to attitude
+	attitude = Quaternion::rotate(attitude, Quaternion::fromRotationVector(rates * dt));
 }
 
-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;
@@ -34,16 +34,9 @@ void applyAcc()
 	if (!landed) return;
 
 	// calculate accelerometer correction
-	Vector up = attitude.rotate(Vector(0, 0, -1));
-	Vector correction = Vector::angularRatesBetweenVectors(acc, up) * dt * WEIGHT_ACC;
+	Vector up = Quaternion::rotateVector(Vector(0, 0, 1), attitude);
+	Vector correction = Vector::rotationVectorBetween(acc, up) * 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);
+	attitude = Quaternion::rotate(attitude, Quaternion::fromRotationVector(correction));
 }

flix/failsafe.ino

@@ -0,0 +1,26 @@
+// 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
+
+extern float controlTime;
+
+// RC loss failsafe
+void failsafe() {
+	if (t - controlTime > RC_LOSS_TIMEOUT) {
+		descend();
+	}
+}
+
+// Smooth descend on RC lost
+void descend() {
+	mode = STAB;
+	controlRoll = 0;
+	controlPitch = 0;
+	controlYaw = 0;
+	controlThrottle -= dt / DESCEND_TIME;
+	if (controlThrottle < 0) controlThrottle = 0;
+}

flix/flix.ino

@@ -5,63 +5,46 @@
 
 #include "vector.h"
 #include "quaternion.h"
+#include "util.h"
 
 #define SERIAL_BAUDRATE 115200
-
-#define WIFI_ENABLED 0
-
-#define RC_CHANNELS 6
-#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_MODE 5
-
-#define MOTOR_REAR_LEFT 0
-#define MOTOR_FRONT_LEFT 3
-#define MOTOR_FRONT_RIGHT 2
-#define MOTOR_REAR_RIGHT 1
+#define WIFI_ENABLED 1
 
 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 controls[RC_CHANNELS]; // normalized controls in range [-1..1] ([0..1] for throttle)
-Vector rates; // angular rates, rad/s
+float controlRoll, controlPitch, controlYaw, controlThrottle, controlArmed, controlMode; // pilot's inputs, range [-1, 1]
+Vector gyro; // gyroscope data
 Vector acc; // accelerometer data, m/s/s
+Vector rates; // filtered angular rates, rad/s
 Quaternion attitude; // estimated attitude
-float motors[4]; // normalized motors thrust in range [-1..1]
+float motors[4]; // normalized motors thrust in range [0..1]
 
-void setup()
-{
+void setup() {
 	Serial.begin(SERIAL_BAUDRATE);
-	Serial.println("Initializing flix");
+	Serial.println("Initializing flix\n");
+	disableBrownOut();
 	setupLED();
 	setupMotors();
 	setLED(true);
-#if WIFI_ENABLED == 1
+#if WIFI_ENABLED
 	setupWiFi();
 #endif
 	setupIMU();
 	setupRC();
-
 	setLED(false);
-	Serial.println("Initializing complete");
+	Serial.println("Initializing complete\n");
 }
 
-void loop()
-{
-	if (!readIMU()) return;
-
+void loop() {
+	readIMU();
 	step();
 	readRC();
 	estimate();
 	control();
 	sendMotors();
-	parseInput();
-#if WIFI_ENABLED == 1
-	sendMavlink();
+	handleInput();
+#if WIFI_ENABLED
+	processMavlink();
 #endif
 	logData();
 }

flix/imu.ino

@@ -5,101 +5,134 @@
 
 #include <SPI.h>
 #include <MPU9250.h>
+#include "util.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);
+// NOTE: use 'ca' command to calibrate the accelerometer and put the values here
+Vector accBias;
+Vector accScale(1, 1, 1);
+Vector gyroBias;
 
-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();
-	}
-
-	loadAccelCal();
-
-	IMU.setSrd(0); // set sample rate to 1000 Hz
-	// NOTE: very important, without the above the rate would be terrible 50 Hz
+	configureIMU();
+	calibrateGyro();
 }
 
-bool readIMU()
-{
-	if (IMU.readSensor() < 0) {
-		Serial.println("IMU read error");
-		return false;
-	}
-
-	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 configureIMU() {
+	IMU.setAccelRange(IMU.ACCEL_RANGE_4G);
+	IMU.setGyroRange(IMU.GYRO_RANGE_2000DPS);
+	IMU.setDLPF(IMU.DLPF_MAX);
+	IMU.setRate(IMU.RATE_1KHZ_APPROX);
 }
 
-void calibrateGyro()
-{
+void readIMU() {
+	IMU.waitForData();
+	IMU.getGyro(gyro.x, gyro.y, gyro.z);
+	IMU.getAccel(acc.x, acc.y, acc.z);
+	// apply scale and bias
+	acc = (acc - accBias) / accScale;
+	gyro = gyro - gyroBias;
+	// rotate
+	rotateIMU(acc);
+	rotateIMU(gyro);
+}
+
+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() {
+	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);
-	printIMUCal();
+	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;
+
+	printIMUCalibration();
+	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();
-	printIMUCal();
+void calibrateAccel() {
+	Serial.println("Calibrating accelerometer");
+	IMU.setAccelRange(IMU.ACCEL_RANGE_2G); // the most sensitive mode
+
+	Serial.setTimeout(60000);
+	Serial.print("1/6 Place level [enter] ");
+	Serial.readStringUntil('\n');
+	calibrateAccelOnce();
+	Serial.print("2/6 Place nose up [enter] ");
+	Serial.readStringUntil('\n');
+	calibrateAccelOnce();
+	Serial.print("3/6 Place nose down [enter] ");
+	Serial.readStringUntil('\n');
+	calibrateAccelOnce();
+	Serial.print("4/6 Place on right side [enter] ");
+	Serial.readStringUntil('\n');
+	calibrateAccelOnce();
+	Serial.print("5/6 Place on left side [enter] ");
+	Serial.readStringUntil('\n');
+	calibrateAccelOnce();
+	Serial.print("6/6 Place upside down [enter] ");
+	Serial.readStringUntil('\n');
+	calibrateAccelOnce();
+
+	printIMUCalibration();
+	Serial.print("✓ Calibration done!\n");
+	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;
+	// 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 printIMUCalibration() {
+	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 +1,23 @@
 // 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);
-}
-
-void blinkLED()
-{
-	setLED(micros() / BLINK_PERIOD % 2);
+	state = on;
 }

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;
@@ -27,12 +26,12 @@ void logData()
 	logBuffer[logPointer][4] = ratesTarget.x;
 	logBuffer[logPointer][5] = ratesTarget.y;
 	logBuffer[logPointer][6] = ratesTarget.z;
-	logBuffer[logPointer][7] = attitude.toEulerZYX().x;
-	logBuffer[logPointer][8] = attitude.toEulerZYX().y;
-	logBuffer[logPointer][9] = attitude.toEulerZYX().z;
-	logBuffer[logPointer][10] = attitudeTarget.toEulerZYX().x;
-	logBuffer[logPointer][11] = attitudeTarget.toEulerZYX().y;
-	logBuffer[logPointer][12] = attitudeTarget.toEulerZYX().z;
+	logBuffer[logPointer][7] = attitude.toEuler().x;
+	logBuffer[logPointer][8] = attitude.toEuler().y;
+	logBuffer[logPointer][9] = attitude.toEuler().z;
+	logBuffer[logPointer][10] = attitudeTarget.toEuler().x;
+	logBuffer[logPointer][11] = attitudeTarget.toEuler().y;
+	logBuffer[logPointer][12] = attitudeTarget.toEuler().z;
 	logBuffer[logPointer][13] = thrustTarget;
 
 	logPointer++;
@@ -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;
 		}
@@ -24,16 +22,15 @@ public:
 			output = input;
 			initialized = true;
 		}
-		return output = output * (1 - alpha) + input * alpha;
+
+		return output += alpha * (input - output);
 	}
 
-	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

@@ -3,16 +3,24 @@
 
 // MAVLink communication
 
-#if WIFI_ENABLED == 1
+#if WIFI_ENABLED
 
-#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()
-{
+extern float controlTime;
+
+void processMavlink() {
+	sendMavlink();
+	receiveMavlink();
+}
+
+void sendMavlink() {
 	static float lastSlow = 0;
 	static float lastFast = 0;
 
@@ -22,8 +30,8 @@ void sendMavlink()
 	if (t - lastSlow >= PERIOD_SLOW) {
 		lastSlow = t;
 
-		mavlink_msg_heartbeat_pack(SYSTEM_ID, MAV_COMP_ID_AUTOPILOT1, &msg, MAV_TYPE_QUADROTOR,
-			MAV_AUTOPILOT_GENERIC, MAV_MODE_FLAG_MANUAL_INPUT_ENABLED | armed ? MAV_MODE_FLAG_SAFETY_ARMED : 0,
+		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) | ((mode == STAB) * MAV_MODE_FLAG_STABILIZE_ENABLED),
 			0, MAV_STATE_STANDBY);
 		sendMessage(&msg);
 	}
@@ -33,33 +41,62 @@ void sendMavlink()
 
 		const float zeroQuat[] = {0, 0, 0, 0};
 		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, attitude.w, attitude.x, -attitude.y, -attitude.z, rates.x, -rates.y, -rates.z, zeroQuat); // convert to frd
 		sendMessage(&msg);
 
-		mavlink_msg_rc_channels_scaled_pack(SYSTEM_ID, MAV_COMP_ID_AUTOPILOT1, &msg, 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);
+		mavlink_msg_rc_channels_raw_pack(SYSTEM_ID, MAV_COMP_ID_AUTOPILOT1, &msg, controlTime * 1000, 0,
+			channels[0], channels[1], channels[2], channels[3], channels[4], channels[5], channels[6], channels[7], UINT8_MAX);
 		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,
+			acc.x * 1000, -acc.y * 1000, -acc.z * 1000, // convert to frd
+			gyro.x * 1000, -gyro.y * 1000, -gyro.z * 1000,
 			0, 0, 0, 0);
 		sendMessage(&msg);
 	}
 }
 
-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) {
+	const mavlink_message_t& msg = *(mavlink_message_t *)_msg;
+
+	if (msg.msgid == MAVLINK_MSG_ID_MANUAL_CONTROL) {
+		mavlink_manual_control_t m;
+		mavlink_msg_manual_control_decode(&msg, &m);
+		controlThrottle = m.z / 1000.0f;
+		controlPitch = m.x / 1000.0f * MAVLINK_CONTROL_SCALE;
+		controlRoll = m.y / 1000.0f * MAVLINK_CONTROL_SCALE;
+		controlYaw = m.r / 1000.0f * MAVLINK_CONTROL_SCALE;
+		controlMode = 1; // STAB mode
+		controlArmed = 1; // armed
+		controlTime = t;
+
+		if (abs(controlYaw) < MAVLINK_CONTROL_YAW_DEAD_ZONE) controlYaw = 0;
+	}
+}
+
 #endif

flix/motors.ino

@@ -1,75 +1,61 @@
 // Copyright (c) 2023 Oleg Kalachev <okalachev@gmail.com>
 // Repository: https://github.com/okalachev/flix
 
-// Motors output control
-// Motor: 8520 3.7V
-// ESC: KINGDUO Micro Mini 4A 1S Brushed Esc 3.6-6V
+// Motors output control using MOSFETs
 
-#define MOTOR_0_PIN 12
-#define MOTOR_1_PIN 13
-#define MOTOR_2_PIN 14
-#define MOTOR_3_PIN 15
+#include "util.h"
 
-#define PWM_FREQUENCY 200
-#define PWM_RESOLUTION 8
+#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_NEUTRAL 1500
+#define PWM_FREQUENCY 78000
+#define PWM_RESOLUTION 10
 
-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};
+// Motors array indexes:
+const int MOTOR_REAR_LEFT = 0;
+const int MOTOR_REAR_RIGHT = 1;
+const int MOTOR_FRONT_RIGHT = 2;
+const int MOTOR_FRONT_LEFT = 3;
 
 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]);
-	}
+int getDutyCycle(float value) {
+	value = constrain(value, 0, 1);
+	float duty = mapff(value, 0, 1, 0, (1 << PWM_RESOLUTION) - 1);
+	return round(duty);
 }
 
-uint8_t pwmToDutyCycle(uint16_t pwm) {
-	return map(pwm, 0, 1000000 / PWM_FREQUENCY, 0, (1 << PWM_RESOLUTION) - 1);
+void sendMotors() {
+	ledcWrite(MOTOR_0_PIN, getDutyCycle(motors[0]));
+	ledcWrite(MOTOR_1_PIN, getDutyCycle(motors[1]));
+	ledcWrite(MOTOR_2_PIN, getDutyCycle(motors[2]));
+	ledcWrite(MOTOR_3_PIN, getDutyCycle(motors[3]));
 }
 
-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)));
+bool motorsActive() {
+	return motors[0] != 0 || motors[1] != 0 || motors[2] != 0 || motors[3] != 0;
 }
 
-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 testMotor(int 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(3000);
+	motors[n] = 0;
+	sendMotors();
+	Serial.printf("Done\n");
 }

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

@@ -15,36 +15,28 @@ public:
 
 	Quaternion(float w, float x, float y, float z): w(w), x(x), y(y), z(z) {};
 
-	static Quaternion fromAxisAngle(float a, float b, float c, float angle)
-	{
+	static Quaternion fromAxisAngle(const Vector& axis, float angle) {
 		float halfAngle = angle * 0.5;
 		float sin2 = sin(halfAngle);
 		float cos2 = cos(halfAngle);
-		float sinNorm = sin2 / sqrt(a * a + b * b + c * c);
-		return Quaternion(cos2, a * sinNorm, b * sinNorm, c * sinNorm);
+		float sinNorm = sin2 / axis.norm();
+		return Quaternion(cos2, axis.x * sinNorm, axis.y * sinNorm, axis.z * sinNorm);
 	}
 
-	static Quaternion fromAngularRates(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)
-	{
-		if (rates.zero()) {
+	static Quaternion fromRotationVector(const Vector& rotation) {
+		if (rotation.zero()) {
 			return Quaternion();
 		}
-		return Quaternion::fromAxisAngle(rates.x, rates.y, rates.z, rates.norm());
+		return Quaternion::fromAxisAngle(rotation, rotation.norm());
 	}
 
-	static Quaternion fromEulerZYX(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 fromEuler(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 +60,70 @@ public:
 		return ret;
 	}
 
-	void toAxisAngle(float& a, float& b, float& c, float& angle)
-	{
+	bool finite() const {
+		return isfinite(w) && isfinite(x) && isfinite(y) && isfinite(z);
+	}
+
+	float norm() const {
+		return sqrt(w * w + x * x + y * y + z * z);
+	}
+
+	void normalize() {
+		float n = norm();
+		w /= n;
+		x /= n;
+		y /= n;
+		z /= n;
+	}
+
+	void toAxisAngle(Vector& axis, float& angle) const {
 		angle = acos(w) * 2;
-		a = x / sin(angle / 2);
-		b = y / sin(angle / 2);
-		c = z / sin(angle / 2);
+		axis.x = x / sin(angle / 2);
+		axis.y = y / sin(angle / 2);
+		axis.z = 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 toRotationVector() const {
+		if (w == 1 && x == 0 && y == 0 && z == 0) return Vector(0, 0, 0); // neutral quaternion
+		float angle;
+		Vector axis;
+		toAxisAngle(axis, angle);
+		return angle * axis;
 	}
 
-	float getYaw() const
-	{
+	Vector toEuler() 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 {
 		// 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) {
@@ -106,25 +134,14 @@ public:
 		return yaw;
 	}
 
-	void setYaw(float yaw)
-	{
+	void setYaw(float yaw) {
 		// TODO: optimize?
-		Vector euler = toEulerZYX();
-		(*this) = Quaternion::fromEulerZYX(euler.x, euler.y, yaw);
+		Vector euler = toEuler();
+		euler.z = yaw;
+		(*this) = Quaternion::fromEuler(euler);
 	}
 
-	Quaternion& operator *= (const Quaternion& q)
-	{
-		Quaternion ret(
-			w * q.w - x * q.x - y * q.y - z * q.z,
-			w * q.x + x * q.w + y * q.z - z * q.y,
-			w * q.y + y * q.w + z * q.x - x * q.z,
-			w * q.z + z * q.w + x * q.y - y * q.x);
-		return (*this = ret);
-	}
-
-	Quaternion operator * (const Quaternion& q)
-	{
+	Quaternion operator * (const Quaternion& q) const {
 		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 +149,15 @@ public:
 			w * q.z + z * q.w + x * q.y - y * q.x);
 	}
 
-	Quaternion inversed() const
-	{
+	bool operator == (const Quaternion& q) const {
+		return w == q.w && x == q.x && y == q.y && z == q.z;
+	}
+
+	bool operator != (const Quaternion& q) const {
+		return !(*this == q);
+	}
+
+	Quaternion inversed() const {
 		float normSqInv = 1 / (w * w + x * x + y * y + z * z);
 		return Quaternion(
 			w * normSqInv,
@@ -142,42 +166,39 @@ public:
 			-z * normSqInv);
 	}
 
-	float norm() const
-	{
-		return sqrt(w * w + x * x + y * y + z * z);
-	}
-
-	void normalize()
-	{
-		float n = norm();
-		w /= n;
-		x /= n;
-		y /= n;
-		z /= n;
-	}
-
-	Vector conjugate(const Vector& v)
-	{
+	Vector conjugate(const Vector& v) const {
 		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) const {
 		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)
-	{
-		return conjugateInversed(v);
+	// Rotate quaternion by quaternion
+	static Quaternion rotate(const Quaternion& a, const Quaternion& b, const bool normalize = true) {
+		Quaternion rotated = a * b;
+		if (normalize) {
+			rotated.normalize();
+		}
+		return rotated;
 	}
 
-	inline bool finite() const
-	{
-		return isfinite(w) && isfinite(x) && isfinite(y) && isfinite(z);
+	// Rotate vector by quaternion
+	static Vector rotateVector(const Vector& v, const Quaternion& q) {
+		return q.conjugateInversed(v);
+	}
+
+	// Quaternion between two quaternions a and b
+	static Quaternion between(const Quaternion& a, const Quaternion& b, const bool normalize = true) {
+		Quaternion q = a * b.inversed();
+		if (normalize) {
+			q.normalize();
+		}
+		return q;
 	}
 
 	size_t printTo(Print& p) const {

flix/rc.ino

@@ -4,30 +4,77 @@
 // Work with the RC receiver
 
 #include <SBUS.h>
+#include "util.h"
 
-const uint16_t channelNeutral[] = {995, 883, 200, 972, 512, 512};
-const uint16_t channelMax[] = {1651, 1540, 1713, 1630, 1472, 1472};
+SBUS RC(Serial2); // NOTE: Use RC(Serial2, 16, 17) if you use the old UART2 pins
 
-SBUS RC(Serial2);
+uint16_t channels[16]; // raw rc channels
+float controlTime; // time of the last controls update
 
-void setupRC()
-{
+
+// NOTE: use 'cr' command to calibrate the RC and put the values here
+int channelZero[] = {992, 992, 172, 992, 172, 172, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
+int channelMax[] = {1811, 1811, 1811, 1811, 1811, 1811, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
+
+// Channels mapping:
+int rollChannel = 0;
+int pitchChannel = 1;
+int throttleChannel = 2;
+int yawChannel = 3;
+int armedChannel = 4;
+int modeChannel = 5;
+
+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; }
+bool readRC() {
+	if (RC.read()) {
+		SBUSData data = RC.data();
+		for (int i = 0; i < 16; i++) channels[i] = data.ch[i]; // copy channels data
 		normalizeRC();
+		controlTime = t;
+		return true;
 	}
+	return false;
 }
 
-static void normalizeRC() {
-	for (uint8_t i = 0; i < RC_CHANNELS; i++) {
-		controls[i] = mapf(channels[i], channelNeutral[i], channelMax[i], 0, 1);
+void normalizeRC() {
+	float controls[16];
+	for (int i = 0; i < 16; i++) {
+		controls[i] = mapf(channels[i], channelZero[i], channelMax[i], 0, 1);
 	}
+	// Update control values
+	controlRoll = controls[rollChannel];
+	controlPitch = controls[pitchChannel];
+	controlYaw = controls[yawChannel];
+	controlThrottle = controls[throttleChannel];
+	controlArmed = controls[armedChannel];
+	controlMode = controls[modeChannel];
+}
+
+void calibrateRC() {
+	Serial.println("Calibrate RC: move all sticks to maximum positions [4 sec]");
+	Serial.println("··o     ··o\n···     ···\n···     ···");
+	delay(4000);
+	while (!readRC());
+	for (int i = 0; i < 16; i++) {
+		channelMax[i] = channels[i];
+	}
+	Serial.println("Calibrate RC: move all sticks to neutral positions [4 sec]");
+	Serial.println("···     ···\n···     ·o·\n·o·     ···");
+	delay(4000);
+	while (!readRC());
+	for (int i = 0; i < 16; i++) {
+		channelZero[i] = channels[i];
+	}
+	printRCCalibration();
+}
+
+void printRCCalibration() {
+	for (int i = 0; i < sizeof(channelZero) / sizeof(channelZero[0]); i++) Serial.printf("%d ", channelZero[i]);
+	Serial.printf("\n");
+	for (int i = 0; i < sizeof(channelMax) / sizeof(channelMax[0]); i++) Serial.printf("%d ", channelMax[i]);
+	Serial.printf("\n");
 }

flix/time.ino

@@ -3,8 +3,9 @@
 
 // Time related functions
 
-void step()
-{
+float loopRate; // Hz
+
+void step() {
 	float now = micros() / 1000000.0;
 	dt = now - t;
 	t = now;
@@ -13,17 +14,16 @@ 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.h

@@ -3,31 +3,24 @@
 
 // Utility functions
 
-#include "math.h"
+#pragma once
 
-float mapf(long x, long in_min, long in_max, float out_min, float out_max)
-{
+#include <math.h>
+#include <soc/soc.h>
+#include <soc/rtc_cntl_reg.h>
+
+const float ONE_G = 9.80665;
+
+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 +29,8 @@ float wrapAngle(float angle)
 	}
 	return angle;
 }
+
+// Disable reset on low voltage
+void disableBrownOut() {
+	REG_CLR_BIT(RTC_CNTL_BROWN_OUT_REG, RTC_CNTL_BROWN_OUT_ENA);
+}

flix/vector.h

@@ -5,8 +5,7 @@
 
 #pragma once
 
-class Vector : public Printable
-{
+class Vector : public Printable {
 public:
 	float x, y, z;
 
@@ -14,79 +13,91 @@ public:
 
 	Vector(float x, float y, float z): x(x), y(y), z(z) {};
 
-	float norm() const
-	{
-		return sqrt(x * x + y * y + z * z);
-	}
-
-	bool zero() const
-	{
+	bool zero() const {
 		return x == 0 && y == 0 && z == 0;
 	}
 
-	void normalize()
-	{
+	bool finite() const {
+		return isfinite(x) && isfinite(y) && isfinite(z);
+	}
+
+	float norm() const {
+		return sqrt(x * x + y * y + z * z);
+	}
+
+	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 {
 		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
-	{
+	Vector& operator += (const Vector& b) {
+		return *this = *this + b;
+	}
+
+	Vector& operator -= (const Vector& b) {
+		return *this = *this - b;
+	}
+
+	// Element-wise multiplication
+	Vector operator * (const Vector& b) const {
+		return Vector(x * b.x, y * b.y, z * b.z);
+	}
+
+	// Element-wise division
+	Vector operator / (const Vector& b) const {
+		return Vector(x / b.x, y / b.y, z / b.z);
+	}
+
+	bool operator == (const Vector& b) const {
 		return x == b.x && y == b.y && z == b.z;
 	}
 
-	inline bool operator != (const Vector& b) const
-	{
+	bool operator != (const Vector& b) const {
 		return !(*this == b);
 	}
 
-	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 angleBetween(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 rotationVectorBetween(const Vector& a, const Vector& b) {
+		Vector direction = cross(a, b);
+		if (direction.zero()) {
+			// vectors are opposite, return any perpendicular vector
+			return cross(a, Vector(1, 0, 0));
+		}
 		direction.normalize();
-		float angle = angleBetweenVectors(u, v);
+		float angle = angleBetween(a, b);
 		return direction * angle;
 	}
 
@@ -97,3 +108,6 @@ public:
 			p.print(z, 15);
 	}
 };
+
+Vector operator * (const float a, const Vector& b) { return b * a; }
+Vector operator + (const float a, const Vector& b) { return b + a; }

flix/wifi.ino

@@ -3,33 +3,34 @@
 
 // Wi-Fi support
 
-#if WIFI_ENABLED == 1
+#if WIFI_ENABLED
 
 #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"
-#define WIFI_UDP_IP "255.255.255.255"
 #define WIFI_UDP_PORT 14550
+#define WIFI_UDP_REMOTE_PORT 14550
 
 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)
-{
-	udp.beginPacket(WIFI_UDP_IP, WIFI_UDP_PORT);
+void sendWiFi(const uint8_t *buf, int len) {
+	udp.beginPacket(WiFi.softAPBroadcastIP(), WIFI_UDP_REMOTE_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)))
 
@@ -44,8 +47,7 @@ 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 +55,43 @@ 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());
 	}
 };
@@ -102,7 +99,7 @@ public:
 class HardwareSerial: public Print {
 public:
 	void begin(unsigned long baud) {
-		// server is running in background by default, so doesn't have access to stdin
+		// server is running in background by default, so it doesn't have access to stdin
 		// https://github.com/gazebosim/gazebo-classic/blob/d45feeb51f773e63960616880b0544770b8d1ad7/gazebo/gazebo_main.cc#L216
 		// set foreground process group to current process group to allow reading from stdin
 		// https://stackoverflow.com/questions/58918188/why-is-stdin-not-propagated-to-child-process-of-different-process-group
@@ -120,12 +117,14 @@ 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;
@@ -134,8 +133,12 @@ void delay(uint32_t ms) {
 	std::this_thread::sleep_for(std::chrono::milliseconds(ms));
 }
 
+bool ledcAttach(uint8_t pin, uint32_t freq, uint8_t resolution) { return true; }
+bool ledcWrite(uint8_t pin, uint32_t duty) { return true; }
+
 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/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 +1,26 @@
+// 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 joystickInit(); };
+	SBUSData data() {
+		SBUSData data;
+		joystickGet(data.ch);
+		for (int i = 0; i < 16; i++) {
+			data.ch[i] = map(data.ch[i], -32768, 32767, 1000, 2000); // convert to pulse width style
+		}
+		return data;
+	};
+};

gazebo/flix.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

@@ -8,42 +8,46 @@
 #include "vector.h"
 #include "quaternion.h"
 #include "Arduino.h"
+#include "wifi.h"
 
-#define RC_CHANNELS 6
-
-#define MOTOR_REAR_LEFT 0
-#define MOTOR_FRONT_LEFT 3
-#define MOTOR_FRONT_RIGHT 2
-#define MOTOR_REAR_RIGHT 1
+#define WIFI_ENABLED 1
 
 float t = NAN;
 float dt;
-float loopFreq;
 float motors[4];
-int16_t channels[16]; // raw rc channels WARNING: unsigned on hardware
-float controls[RC_CHANNELS];
+float controlRoll, controlPitch, controlYaw, controlThrottle, controlArmed, controlMode;
 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();
 void controlRate();
 void controlTorque();
 void showTable();
+void sendMotors();
 bool motorsActive();
-void cliTestMotor(uint8_t n);
+void doCommand(const String& command);
+void normalizeRC();
+void printRCCalibration();
+void processMavlink();
+void sendMavlink();
+void sendMessage(const void *msg);
+void receiveMavlink();
+void handleMavlink(const void *_msg);
+void failsafe();
+void descend();
+inline Quaternion fluToFrd(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 printIMUCalibration() { printf("cal: N/A\n"); };
+void printIMUInfo() {};

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 +7,59 @@
 #include <gazebo/gazebo.hh>
 #include <iostream>
 
-using namespace std;
+// simulation calibration overrides, NOTE: use `cr` command and replace with the actual values
+const int channelZeroOverride[] = {1500, 0, 1000, 1500, 1500, 1000};
+const int channelMaxOverride[] = {2000, 2000, 2000, 2000, 2000, 2000};
 
-static const int16_t channelNeutralMin[] = {-1290,	-258,	-26833,	0,	0, 0};
-static const int16_t channelNeutralMax[] = {-1032,	-258,	-27348,	3353,	0, 0};
+// channels mapping overrides
+const int rollChannelOverride = 3;
+const int pitchChannelOverride = 4;
+const int throttleChannelOverride = 5;
+const int yawChannelOverride = 0;
+const int armedChannelOverride = 2;
+const int modeChannelOverride = 1;
 
-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;
-
-bool joystickInitialized = false, warnShown = false;
+SDL_Joystick *joystick;
 
 void normalizeRC();
 
-void joystickInit()
-{
+bool joystickInit() {
+	static bool joystickInitialized = false;
+	static bool warnShown = false;
+	if (joystickInitialized) return true;
+
 	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;
 	}
+
+	// apply overrides
+	extern int channelZero[16];
+	extern int channelMax[16];
+	memcpy(channelZero, channelZeroOverride, sizeof(channelZeroOverride));
+	memcpy(channelMax, channelMaxOverride, sizeof(channelMaxOverride));
+
+	extern int rollChannel, pitchChannel, throttleChannel, yawChannel, armedChannel, modeChannel;
+	rollChannel = rollChannelOverride;
+	pitchChannel = pitchChannelOverride;
+	throttleChannel = throttleChannelOverride;
+	yawChannel = yawChannelOverride;
+	armedChannel = armedChannelOverride;
+	modeChannel = modeChannelOverride;
+
+	return joystickInitialized;
 }
 
-void joystickGet()
-{
-	if (!joystickInitialized) {
-		joystickInit();
-		return;
-	}
-
+bool joystickGet(int16_t ch[16]) {
 	SDL_JoystickUpdate();
 
-	for (uint8_t i = 0; i < 4; i++) {
-		channels[i] = SDL_JoystickGetAxis(joystick, i);
+	for (uint8_t i = 0; i < 16; 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

@@ -1,6 +1,7 @@
 <?xml version="1.0"?>
 <sdf version="1.5">
 	<model name="flix">
+		<plugin name="flix" filename="libflix.so"/>
 		<link name="body">
 			<inertial>
 				<mass>0.065</mass>
@@ -13,57 +14,58 @@
 			<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>
 				<update_rate>1000</update_rate>
 				<imu>
 					<angular_velocity>
-						<x>
-							<noise type="gaussian">
-								<stddev>0.00174533</stddev><!-- 0.1 degrees per second -->
-							</noise>
-						</x>
-						<y>
-							<noise type="gaussian">
-								<stddev>0.00174533</stddev>
-							</noise>
-						</y>
-						<z>
-							<noise type="gaussian">
-								<stddev>0.00174533</stddev>
-							</noise>
-						</z>
+						<x><noise type="gaussian"><stddev>0.00174533</stddev></noise></x><!-- 0.1 degrees per second -->
+						<y><noise type="gaussian"><stddev>0.00174533</stddev></noise></y>
+						<z><noise type="gaussian"><stddev>0.00174533</stddev></noise></z>
 					</angular_velocity>
 					<linear_acceleration>
-						<x>
-							<noise type="gaussian">
-								<stddev>0.0784</stddev><!-- 8 mg -->
-							</noise>
-						</x>
-						<y>
-							<noise type="gaussian">
-								<stddev>0.0784</stddev>
-							</noise>
-						</y>
-						<z>
-							<noise type="gaussian">
-								<stddev>0.0784</stddev>
-							</noise>
-						</z>
+						<x><noise type="gaussian"><stddev>0.0784</stddev></noise></x><!-- 8 mg -->
+						<y><noise type="gaussian"><stddev>0.0784</stddev></noise></y>
+						<z><noise type="gaussian"><stddev>0.0784</stddev></noise></z>
 					</linear_acceleration>
 				</imu>
 			</sensor>
+			<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>
 </sdf>

gazebo/simulator.cpp

@@ -0,0 +1,134 @@
+// 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 "rc.ino"
+#include "time.ino"
+#include "motors.ino"
+#include "estimate.ino"
+#include "control.ino"
+#include "log.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);
+		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();
+		controlMode = 1; // 0 acro, 1 stab
+		controlArmed = 1; // armed
+
+		estimate();
+
+		// correct yaw to the actual yaw
+		attitude.setYaw(this->model->WorldPose().Yaw());
+
+		control();
+		handleInput();
+		processMavlink();
+
+		applyMotorForces();
+		publishTopics();
+		logData();
+	}
+
+	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 Flix' util.h

gazebo/soc/soc.h

@@ -0,0 +1,4 @@
+// Dummy file to make it possible to compile simulator with Flix' util.h
+
+#define WRITE_PERI_REG(addr, val) {}
+#define REG_CLR_BIT(_r, _b) {}

gazebo/wifi.h

@@ -0,0 +1,44 @@
+// Copyright (c) 2023 Oleg Kalachev <okalachev@gmail.com>
+// Repository: https://github.com/okalachev/flix
+
+// sendWiFi and receiveWiFi implementations for the simulation
+
+#include <arpa/inet.h>
+#include <netinet/in.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <unistd.h>
+#include <sys/poll.h>
+#include <gazebo/gazebo.hh>
+
+#define WIFI_UDP_PORT 14580
+#define WIFI_UDP_REMOTE_PORT 14550
+
+int wifiSocket;
+
+void setupWiFi() {
+	wifiSocket = socket(AF_INET, SOCK_DGRAM, 0);
+	sockaddr_in addr; // local address
+	addr.sin_family = AF_INET;
+	addr.sin_addr.s_addr = INADDR_ANY;
+	addr.sin_port = htons(WIFI_UDP_PORT);
+	bind(wifiSocket, (sockaddr *)&addr, sizeof(addr));
+	int broadcast = 1;
+	setsockopt(wifiSocket, SOL_SOCKET, SO_BROADCAST, &broadcast, sizeof(broadcast)); // enable broadcast
+	gzmsg << "WiFi UDP socket initialized on port " << WIFI_UDP_PORT << " (remote port " << WIFI_UDP_REMOTE_PORT << ")" << std::endl;
+}
+
+void sendWiFi(const uint8_t *buf, int len) {
+	if (wifiSocket == 0) setupWiFi();
+	sockaddr_in addr; // remote address
+	addr.sin_family = AF_INET;
+	addr.sin_addr.s_addr = INADDR_BROADCAST; // send UDP broadcast
+	addr.sin_port = htons(WIFI_UDP_REMOTE_PORT);
+	sendto(wifiSocket, buf, len, 0, (sockaddr *)&addr, sizeof(addr));
+}
+
+int receiveWiFi(uint8_t *buf, int len) {
+	struct pollfd pfd = { .fd = wifiSocket, .events = POLLIN };
+	if (poll(&pfd, 1, 0) <= 0) return 0; // check if there is data to read
+	return recv(wifiSocket, buf, len, 0);
+}

tools/check_c_cpp_properties.py

@@ -0,0 +1,61 @@
+#!/usr/bin/env python3
+
+import os
+import platform
+import json
+import re
+
+path = '.vscode/c_cpp_properties.json' if os.path.exists('./.vscode/c_cpp_properties.json') else '../.vscode/c_cpp_properties.json'
+txt = open(path).read()
+# remove comments
+txt = re.sub(r'//.*', '', txt)
+props = json.loads(txt)
+
+env = props.get('env', {})
+env['workspaceFolder'] = '.'
+
+def check_path(s):
+    source = s
+    # replace env
+    for key, value in env.items():
+        s = s.replace('${' + key + '}', value)
+    # remove globs from the end
+    if s.endswith('**'):
+        s = s[:-2]
+    elif s.endswith('*'):
+        s = s[:-1]
+    s = os.path.expanduser(s)
+    if s == '':
+        s = '.'
+    print('Check', source, '->', s)
+    assert os.path.exists(s), 'Path does not exist: ' + s
+
+# linux, macos or windows:
+platform = platform.system().lower()
+if platform == 'darwin':
+    platform = 'mac'
+elif platform == 'windows':
+    platform = 'win32'
+elif platform == 'linux':
+    pass
+else:
+    raise Exception('Unknown platform: ' + platform)
+
+for configuration in props['configurations']:
+    if platform not in configuration['name'].lower():
+        print('Skip configuration', configuration['name'])
+        continue
+
+    print('Check configuration', configuration['name'])
+
+    for include_path in configuration.get('includePath', []):
+        check_path(include_path)
+
+    for forced_include in configuration.get('forcedInclude', []):
+        check_path(forced_include)
+
+    for browse in configuration.get('browse', {}).get('path', []):
+        check_path(browse)
+
+    if 'compilerPath' in configuration:
+        check_path(configuration['compilerPath'])

tools/csv_to_mcap.py

@@ -0,0 +1,46 @@
+#!/usr/bin/env python3
+
+"""Convert CSV log file to MCAP file.
+
+Usage:
+  csv_to_mcap.py <csv_file> [<mcap_file>]
+"""
+
+import csv
+import json
+import docopt
+from mcap.writer import Writer
+
+args = docopt.docopt(__doc__)
+input_file = args['<csv_file>']
+output_file = args['<mcap_file>'] or input_file.replace('.csv', '.mcap')
+if input_file == output_file:
+    raise ValueError('Input and output files are the same')
+
+csv_file = open(input_file, 'r')
+csv_reader = csv.reader(csv_file, delimiter=',')
+header = next(csv_reader)
+
+mcap_file = open(output_file, 'wb')
+writer = Writer(mcap_file)
+writer.start()
+
+properties = {key: {'type': 'number'} for key in header}
+schema_id = writer.register_schema(
+    name="state",
+    encoding="jsonschema",
+    data=json.dumps({"type": "object", "properties": properties}).encode(),
+)
+
+channel_id = writer.register_channel(
+    schema_id=schema_id,
+    topic="state",
+    message_encoding="json",
+)
+
+for row in csv_reader:
+    data = {key: float(value) for key, value in zip(header, row)}
+    timestamp = round(float(row[0]) * 1e9)
+    writer.add_message(channel_id=channel_id, log_time=timestamp, data=json.dumps(data).encode(), publish_time=timestamp,)
+
+writer.finish()

tools/csv_to_ulog/CMakeLists.txt

@@ -0,0 +1,23 @@
+cmake_minimum_required(VERSION 3.15)
+project(csv_to_ulog)
+include(FetchContent)
+set(CMAKE_CXX_STANDARD 17)
+
+FetchContent_Declare(
+  ulog_cpp
+  GIT_REPOSITORY https://github.com/PX4/ulog_cpp.git
+  GIT_TAG cf24ec6
+)
+
+FetchContent_Declare(
+  rapidcsv
+  GIT_REPOSITORY https://github.com/d99kris/rapidcsv.git
+  GIT_TAG v8.82
+)
+
+FetchContent_MakeAvailable(ulog_cpp)
+FetchContent_MakeAvailable(rapidcsv)
+
+add_executable(csv_to_ulog csv_to_ulog.cpp)
+target_link_libraries(csv_to_ulog PUBLIC ulog_cpp::ulog_cpp)
+target_include_directories(csv_to_ulog PUBLIC ${rapidcsv_SOURCE_DIR}/src)

tools/csv_to_ulog/README.md

@@ -0,0 +1,20 @@
+# csv_to_ulog
+
+Tool for converting CSV flight logs to ULog format so they can be analyzed using [FlightPlot](https://github.com/PX4/FlightPlot) software.
+
+To build, go to the `<flix>/tools/csv_to_ulog` directory and run:
+
+```bash
+mkdir build
+cd build
+cmake ..
+make
+```
+
+Convert a CSV file to ULog:
+
+```bash
+./csv_to_ulog log_file.csv
+```
+
+ULog file will be saved in the same directory.

tools/csv_to_ulog/csv_to_ulog.cpp

@@ -0,0 +1,72 @@
+// Copyright (c) 2023 Oleg Kalachev <okalachev@gmail.com>
+// Repository: https://github.com/okalachev/flix
+
+// Tool for conversion CSV log file to ULog format
+
+#include <ulog_cpp/simple_writer.hpp>
+#include <rapidcsv.h>
+#include <vector>
+#include <string>
+#include <filesystem>
+
+using std::vector;
+using std::string;
+
+struct Data {
+	uint64_t timestamp;
+	float values[30];
+};
+
+int main(int argc, char** argv)
+{
+	if (argc < 2) {
+		printf("Usage: %s file.csv [file.ulg]\n", argv[0]);
+		return -1;
+	}
+
+	// check input file exists
+	if (!std::filesystem::exists(argv[1])) {
+		printf("Input file \"%s\" does not exist\n", argv[1]);
+		return -1;
+	}
+
+	// open csv file
+	rapidcsv::Document csv(argv[1]);
+	auto columns = csv.GetColumnNames();
+
+
+	// open ulog file
+	string ulog_file;
+	if (argc < 3) {
+		ulog_file = std::filesystem::path(argv[1]).replace_extension(".ulg").string();
+	} else {
+		ulog_file = argv[2];
+	}
+	ulog_cpp::SimpleWriter writer(ulog_file.c_str(), 0);
+	writer.writeInfo("sys_name", "flix");
+
+	vector<ulog_cpp::Field> fields;
+	fields.push_back(ulog_cpp::Field("uint64_t", "timestamp"));
+	columns.erase(columns.begin()); // remove timestamp column
+	for (auto& column : columns) {
+		// Valid field name for ULog: [a-z0-9_]+
+		std::replace(column.begin(), column.end(), '.', '_'); // replace dots with underscores
+		std::transform(column.begin(), column.end(), column.begin(), [](unsigned char c) { return std::tolower(c); }); // lowercase column name
+		fields.push_back(ulog_cpp::Field("float", column));
+	}
+
+	const char* msg_name = "state";
+	writer.writeMessageFormat(msg_name, fields);
+	writer.headerComplete();
+
+	const uint16_t msg_id = writer.writeAddLoggedMessage(msg_name);
+
+	for (size_t i = 0; i < csv.GetRowCount(); i++) {
+		Data data;
+		data.timestamp = csv.GetCell<float>(0, i) * 1000000.0;
+		for (size_t j = 1; j <= columns.size(); j++) {
+			data.values[j - 1] = csv.GetCell<float>(j, i);
+		}
+		writer.writeData(msg_id, data);
+	}
+}

tools/grab_log.py

@@ -9,8 +9,7 @@ PORT = os.environ['PORT']
 DIR = os.path.dirname(os.path.realpath(__file__))
 
 dev = serial.Serial(port=PORT, baudrate=115200, timeout=0.5)
-
-log = open(f'{DIR}/log/{datetime.datetime.now().isoformat()}.csv', 'wb')
+lines = []
 
 print('Downloading log...')
 count = 0
@@ -19,8 +18,14 @@ while True:
     line = dev.readline()
     if not line:
         break
-    log.write(line)
+    lines.append(line)
     count += 1
     print(f'\r{count} lines', end='')
 
+# sort by timestamp
+header = lines.pop(0)
+lines.sort(key=lambda line: float(line.split(b',')[0]))
+
+log = open(f'{DIR}/log/{datetime.datetime.now().isoformat()}.csv', 'wb')
+log.writelines([header] + lines)
 print(f'\nWritten {os.path.relpath(log.name, os.curdir)}')

tools/requirements.txt

@@ -0,0 +1,3 @@
+docopt
+matplotlib
+mcap