Another minor fixes

By default the WiFi channel is used

.github/workflows/build.yml

@@ -23,10 +23,10 @@ jobs:
       with:
         name: firmware-binary
         path: flix/build
+    - name: Build firmware for ESP32-C3
+      run: make BOARD=esp32:esp32:esp32c3
     - name: Build firmware for ESP32-S3
       run: make BOARD=esp32:esp32:esp32s3
-    - name: Build firmware with WiFi disabled
-      run: sed -i 's/^#define WIFI_ENABLED 1$/#define WIFI_ENABLED 0/' flix/flix.ino && make
     - name: Check c_cpp_properties.json
       run: tools/check_c_cpp_properties.py
 

.github/workflows/tools.yml

@@ -46,14 +46,3 @@ jobs:
         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
-
-  sloc:
-    runs-on: ubuntu-latest
-    steps:
-    - uses: actions/checkout@v4
-    - name: Install cloc
-      run: sudo apt-get install -y cloc
-    - name: Firmware source lines count
-      run: cloc --by-file-by-lang flix
-    - name: Overall source lines count
-      run: cloc --by-file-by-lang --exclude-ext=svg,dae,css,hbs,md,json,yaml,yml,toml .

.markdownlint.json

@@ -7,6 +7,8 @@
 	"MD024": false,
 	"MD033": false,
 	"MD034": false,
+	"MD040": false,
+	"MD059": false,
 	"MD044": {
 		"html_elements": false,
 		"code_blocks": false,
@@ -64,5 +66,6 @@
 			"PX4"
 		]
 	},
-	"MD045": false
+	"MD045": false,
+	"MD060": false
 }

.vscode/c_cpp_properties.json

@@ -6,19 +6,18 @@
 				"${workspaceFolder}/flix",
 				"${workspaceFolder}/gazebo",
 				"${workspaceFolder}/tools/**",
-				"~/.arduino15/packages/esp32/hardware/esp32/3.2.0/cores/esp32",
+				"~/.arduino15/packages/esp32/hardware/esp32/3.3.6/cores/esp32",
-				"~/.arduino15/packages/esp32/hardware/esp32/3.2.0/libraries/**",
+				"~/.arduino15/packages/esp32/hardware/esp32/3.3.6/libraries/**",
-				"~/.arduino15/packages/esp32/hardware/esp32/3.2.0/variants/d1_mini32",
+				"~/.arduino15/packages/esp32/hardware/esp32/3.3.6/variants/d1_mini32",
-				"~/.arduino15/packages/esp32/tools/esp32-arduino-libs/idf-release_v5.4-2f7dcd86-v1/esp32/**",
+				"~/.arduino15/packages/esp32/tools/esp32-libs/3.3.6/include/**",
-				"~/.arduino15/packages/esp32/tools/esp32-arduino-libs/idf-release_v5.4-2f7dcd86-v1/esp32/dio_qspi/include",
 				"~/Arduino/libraries/**",
 				"/usr/include/gazebo-11/",
 				"/usr/include/ignition/math6/"
 			],
 			"forcedInclude": [
 				"${workspaceFolder}/.vscode/intellisense.h",
-				"~/.arduino15/packages/esp32/hardware/esp32/3.2.0/cores/esp32/Arduino.h",
+				"~/.arduino15/packages/esp32/hardware/esp32/3.3.6/cores/esp32/Arduino.h",
-				"~/.arduino15/packages/esp32/hardware/esp32/3.2.0/variants/d1_mini32/pins_arduino.h",
+				"~/.arduino15/packages/esp32/hardware/esp32/3.3.6/variants/d1_mini32/pins_arduino.h",
 				"${workspaceFolder}/flix/cli.ino",
 				"${workspaceFolder}/flix/control.ino",
 				"${workspaceFolder}/flix/estimate.ino",
@@ -31,9 +30,10 @@
 				"${workspaceFolder}/flix/rc.ino",
 				"${workspaceFolder}/flix/time.ino",
 				"${workspaceFolder}/flix/wifi.ino",
-				"${workspaceFolder}/flix/parameters.ino"
+				"${workspaceFolder}/flix/parameters.ino",
+				"${workspaceFolder}/flix/safety.ino"
 			],
-			"compilerPath": "~/.arduino15/packages/esp32/tools/esp-x32/2411/bin/xtensa-esp32-elf-g++",
+			"compilerPath": "~/.arduino15/packages/esp32/tools/esp-x32/2511/bin/xtensa-esp32-elf-g++",
 			"cStandard": "c11",
 			"cppStandard": "c++17",
 			"defines": [
@@ -53,19 +53,18 @@
 			"name": "Mac",
 			"includePath": [
 				"${workspaceFolder}/flix",
-				"~/Library/Arduino15/packages/esp32/hardware/esp32/3.2.0/cores/esp32",
+				"~/Library/Arduino15/packages/esp32/hardware/esp32/3.3.6/cores/esp32",
-				"~/Library/Arduino15/packages/esp32/hardware/esp32/3.2.0/libraries/**",
+				"~/Library/Arduino15/packages/esp32/hardware/esp32/3.3.6/libraries/**",
-				"~/Library/Arduino15/packages/esp32/hardware/esp32/3.2.0/variants/d1_mini32",
+				"~/Library/Arduino15/packages/esp32/hardware/esp32/3.3.6/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-libs/3.3.6/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/gazebo-11/",
 				"/opt/homebrew/include/ignition/math6/"
 			],
 			"forcedInclude": [
 				"${workspaceFolder}/.vscode/intellisense.h",
-				"~/Library/Arduino15/packages/esp32/hardware/esp32/3.2.0/cores/esp32/Arduino.h",
+				"~/Library/Arduino15/packages/esp32/hardware/esp32/3.3.6/cores/esp32/Arduino.h",
-				"~/Library/Arduino15/packages/esp32/hardware/esp32/3.2.0/variants/d1_mini32/pins_arduino.h",
+				"~/Library/Arduino15/packages/esp32/hardware/esp32/3.3.6/variants/d1_mini32/pins_arduino.h",
 				"${workspaceFolder}/flix/flix.ino",
 				"${workspaceFolder}/flix/cli.ino",
 				"${workspaceFolder}/flix/control.ino",
@@ -78,9 +77,10 @@
 				"${workspaceFolder}/flix/rc.ino",
 				"${workspaceFolder}/flix/time.ino",
 				"${workspaceFolder}/flix/wifi.ino",
-				"${workspaceFolder}/flix/parameters.ino"
+				"${workspaceFolder}/flix/parameters.ino",
+				"${workspaceFolder}/flix/safety.ino"
 			],
-			"compilerPath": "~/Library/Arduino15/packages/esp32/tools/esp-x32/2411/bin/xtensa-esp32-elf-g++",
+			"compilerPath": "~/Library/Arduino15/packages/esp32/tools/esp-x32/2511/bin/xtensa-esp32-elf-g++",
 			"cStandard": "c11",
 			"cppStandard": "c++17",
 			"defines": [
@@ -103,17 +103,16 @@
 				"${workspaceFolder}/flix",
 				"${workspaceFolder}/gazebo",
 				"${workspaceFolder}/tools/**",
-				"~/AppData/Local/Arduino15/packages/esp32/hardware/esp32/3.2.0/cores/esp32",
+				"~/AppData/Local/Arduino15/packages/esp32/hardware/esp32/3.3.6/cores/esp32",
-				"~/AppData/Local/Arduino15/packages/esp32/hardware/esp32/3.2.0/libraries/**",
+				"~/AppData/Local/Arduino15/packages/esp32/hardware/esp32/3.3.6/libraries/**",
-				"~/AppData/Local/Arduino15/packages/esp32/hardware/esp32/3.2.0/variants/d1_mini32",
+				"~/AppData/Local/Arduino15/packages/esp32/hardware/esp32/3.3.6/variants/d1_mini32",
-				"~/AppData/Local/Arduino15/packages/esp32/tools/esp32-arduino-libs/idf-release_v5.4-2f7dcd86-v1/esp32/**",
+				"~/AppData/Local/Arduino15/packages/esp32/tools/esp32-libs/3.3.6/include/**",
-				"~/AppData/Local/Arduino15/packages/esp32/tools/esp32-arduino-libs/idf-release_v5.4-2f7dcd86-v1/esp32/dio_qspi/include",
 				"~/Documents/Arduino/libraries/**"
 			],
 			"forcedInclude": [
 				"${workspaceFolder}/.vscode/intellisense.h",
-				"~/AppData/Local/Arduino15/packages/esp32/hardware/esp32/3.2.0/cores/esp32/Arduino.h",
+				"~/AppData/Local/Arduino15/packages/esp32/hardware/esp32/3.3.6/cores/esp32/Arduino.h",
-				"~/AppData/Local/Arduino15/packages/esp32/hardware/esp32/3.2.0/variants/d1_mini32/pins_arduino.h",
+				"~/AppData/Local/Arduino15/packages/esp32/hardware/esp32/3.3.6/variants/d1_mini32/pins_arduino.h",
 				"${workspaceFolder}/flix/cli.ino",
 				"${workspaceFolder}/flix/control.ino",
 				"${workspaceFolder}/flix/estimate.ino",
@@ -126,9 +125,10 @@
 				"${workspaceFolder}/flix/rc.ino",
 				"${workspaceFolder}/flix/time.ino",
 				"${workspaceFolder}/flix/wifi.ino",
-				"${workspaceFolder}/flix/parameters.ino"
+				"${workspaceFolder}/flix/parameters.ino",
+				"${workspaceFolder}/flix/safety.ino"
 			],
-			"compilerPath": "~/AppData/Local/Arduino15/packages/esp32/tools/esp-x32/2411/bin/xtensa-esp32-elf-g++.exe",
+			"compilerPath": "~/AppData/Local/Arduino15/packages/esp32/tools/esp-x32/2511/bin/xtensa-esp32-elf-g++.exe",
 			"cStandard": "c11",
 			"cppStandard": "c++17",
 			"defines": [

Makefile

@@ -1,6 +1,5 @@
 BOARD = esp32:esp32:d1_mini32
-PORT := $(wildcard /dev/serial/by-id/usb-Silicon_Labs_CP21* /dev/serial/by-id/usb-1a86_USB_Single_Serial_* /dev/cu.usbserial-*)
+PORT := $(strip $(wildcard /dev/serial/by-id/usb-Silicon_Labs_CP21* /dev/serial/by-id/usb-1a86_USB_Single_Serial_* /dev/cu.usbserial-* /dev/cu.usbmodem*))
-PORT := $(strip $(PORT))
 
 build: .dependencies
 	arduino-cli compile --fqbn $(BOARD) flix
@@ -13,12 +12,16 @@ monitor:
 
 dependencies .dependencies:
 	arduino-cli core update-index --config-file arduino-cli.yaml
-	arduino-cli core install esp32:esp32@3.2.0 --config-file arduino-cli.yaml
+	arduino-cli core install esp32:esp32@3.3.6 --config-file arduino-cli.yaml
 	arduino-cli lib update-index
 	arduino-cli lib install "FlixPeriph"
-	arduino-cli lib install "MAVLink"@2.0.16
+	arduino-cli lib install "MAVLink"@2.0.25
 	touch .dependencies
 
+upload_proxy: .dependencies
+	arduino-cli compile --fqbn $(BOARD) tools/espnow-proxy
+	arduino-cli upload --fqbn $(BOARD) -p "$(PORT)" tools/espnow-proxy
+
 gazebo/build cmake: gazebo/CMakeLists.txt
 	mkdir -p gazebo/build
 	cd gazebo/build && cmake ..

README.md

@@ -1,6 +1,9 @@
-# Flix
+<!-- markdownlint-disable MD041 -->
 
-**Flix** (*flight + X*) — open source ESP32-based quadcopter made from scratch.
+<p align="center">
+  <img src="docs/img/flix.svg" width=180 alt="Flix logo"><br>
+  <b>Flix</b> (<i>flight + X</i>) — open source ESP32-based quadcopter made from scratch.
+</p>
 
 <table>
   <tr>
@@ -18,15 +21,13 @@
 * Dedicated for education and research.
 * Made from general-purpose components.
 * Simple and clean source code in Arduino (<2k lines firmware).
-* Control using USB gamepad, remote control or smartphone.
+* Communication using MAVLink protocol over Wi-Fi or ESP-NOW.
-* Wi-Fi and MAVLink support.
+* Control with USB gamepad, remote control or smartphone.
 * Wireless command line interface and analyzing.
 * Precise simulation with Gazebo.
-* Python library.
+* Python library for scripting and automatic flights.
 * Textbook on flight control theory and practice ([in development](https://quadcopter.dev)).
-* *Position control (using external camera) and autonomous flights¹*.
+* *Position control (planned)*.
-
-*¹ — planned.*
 
 ## It actually flies
 
@@ -52,7 +53,7 @@ The simulator is implemented using Gazebo and runs the original Arduino code:
 
 <img src="docs/img/simulator1.png" width=500 alt="Flix simulator">
 
-## Documentation
+## Documentation articles
 
 1. [Assembly instructions](docs/assembly.md).
 2. [Usage: build, setup and flight](docs/usage.md).
@@ -70,14 +71,14 @@ Additional articles:
 
 |Type|Part|Image|Quantity|
 |-|-|:-:|:-:|
-|Microcontroller board|ESP32 Mini|<img src="docs/img/esp32.jpg" width=100>|1|
+|Microcontroller board|ESP32 Mini.<br>ESP32-S3/ESP32-C3 boards are also supported.|<img src="docs/img/esp32.jpg" width=100>|1|
-|IMU (and barometer¹) board|GY‑91, MPU-9265 (or other MPU‑9250/MPU‑6500 board)<br>ICM20948V2 (ICM‑20948)³<br>GY-521 (MPU-6050)³⁻¹|<img src="docs/img/gy-91.jpg" width=90 align=center><br><img src="docs/img/icm-20948.jpg" width=100><br><img src="docs/img/gy-521.jpg" width=100>|1|
+|IMU (and barometer¹) board|GY‑91, MPU-9265 (or other MPU‑9250/MPU‑6500 board)<br>ICM20948V2 (ICM‑20948)<br>GY-521 (MPU-6050)|<img src="docs/img/gy-91.jpg" width=90 align=center><br><img src="docs/img/icm-20948.jpg" width=100><br><img src="docs/img/gy-521.jpg" width=100>|1|
 |Boost converter (optional, for more stable power supply)|5V output|<img src="docs/img/buck-boost.jpg" width=100>|1|
 |Motor|8520 3.7V brushed motor.<br>Motor with exact 3.7V voltage is needed, not ranged working voltage (3.7V — 6V).<br>Make sure the motor shaft diameter and propeller hole diameter match!|<img src="docs/img/motor.jpeg" width=100>|4|
-|Propeller|55 mm (alternatively 65 mm)|<img src="docs/img/prop.jpg" width=100>|4|
+|Propeller|55 mm or 65 mm|<img src="docs/img/prop.jpg" width=100>|4|
 |MOSFET (transistor)|100N03A or [analog](https://t.me/opensourcequadcopter/33)|<img src="docs/img/100n03a.jpg" width=100>|4|
-|Pull-down resistor|10 kΩ|<img src="docs/img/resistor10k.jpg" width=100>|4|
+|Pull-down resistor<br>Voltage measurement resistor|10 kΩ|<img src="docs/img/resistor10k.jpg" width=100>|6|
-|3.7V Li-Po battery|LW 952540 (or any compatible by the size)|<img src="docs/img/battery.jpg" width=100>|1|
+|3.7V Li-Po battery|LW 952540 (or any compatible by the size).<br>Make sure the battery has enough discharge rate — 25C or more!|<img src="docs/img/battery.jpg" width=100>|1|
 |Battery connector cable|MX2.0 2P female|<img src="docs/img/mx.png" width=100>|1|
 |Li-Po Battery charger|Any|<img src="docs/img/charger.jpg" width=100>|1|
 |Screws for IMU board mounting|M3x5|<img src="docs/img/screw-m3.jpg" width=100>|2|
@@ -137,10 +138,10 @@ You can see a user-contributed [variant of complete circuit diagram](https://mir
 
   |Motor|Position|Direction|Prop type|Motor wires|GPIO|
   |-|-|-|-|-|-|
-  |Motor 0|Rear left|Counter-clockwise|B|Black & White|GPIO12 (*TDI*)|
+  |Motor 0|Rear left|Counter-clockwise|B|Black & White|GPIO12 *(TDI)*|
-  |Motor 1|Rear right|Clockwise|A|Blue & Red|GPIO13 (*TCK*)|
+  |Motor 1|Rear right|Clockwise|A|Blue & Red|GPIO13 *(TCK)*|
-  |Motor 2|Front right|Counter-clockwise|B|Black & White|GPIO14 (*TMS*)|
+  |Motor 2|Front right|Counter-clockwise|B|Black & White|GPIO14 *(TMS)*|
-  |Motor 3|Front left|Clockwise|A|Blue & Red|GPIO15 (*TD0*)|
+  |Motor 3|Front left|Clockwise|A|Blue & Red|GPIO15 *(TD0)*|
 
   Clockwise motors have blue & red wires and correspond to propeller type A (marked on the propeller).
   Counter-clockwise motors have black & white wires correspond to propeller type B.
@@ -151,14 +152,16 @@ You can see a user-contributed [variant of complete circuit diagram](https://mir
   |-|-|
   |GND|GND|
   |VIN|VCC (or 3.3V depending on the receiver)|
-  |Signal (TX)|GPIO4¹|
+  |Signal (TX)|GPIO4|
 
-*¹ — UART2 RX pin was [changed](https://docs.espressif.com/projects/arduino-esp32/en/latest/migration_guides/2.x_to_3.0.html#id14) to GPIO4 in Arduino ESP32 core 3.0.*
+* Optionally connect the battery voltage divider for voltage monitoring to any ADC1 pin (e. g. *GPIO32* on ESP32, *GPIO3* on ESP32-S3).
+
+  ESP32 and ESP32-S3 [can measure](https://docs.espressif.com/projects/arduino-esp32/en/latest/api/adc.html#analogsetattenuation) up to 3.1 V and ESP32-S3/ESP32-C3 can measure up to 2.5 V, so choose the voltage divider resistors accordingly.
 
 ## Resources
 
 * Telegram channel on developing the drone and the flight controller (in Russian): https://t.me/opensourcequadcopter.
-* Official Telegram chat: https://t.me/opensourcequadcopterchat.
+* Official Telegram chat: https://t.me/opensourcequadcopterchat (English / Russian).
 * Detailed article on Habr.com about the development of the drone (in Russian): https://habr.com/ru/articles/814127/.
 
 ## Disclaimer

docs/assembly.md

@@ -28,6 +28,8 @@ Soldered components ([schematics variant](https://miro.com/app/board/uXjVN-dTjoo
 
 <img src="img/assembly/7.jpg" width=600>
 
+See an alternative assembly process photos here: https://drive.google.com/drive/folders/1FG5BH9RCzdf1XmJcC70PymiRMXcz6Fx7?usp=sharing.
+
 ## Motor directions
 
 > [!WARNING]
@@ -41,10 +43,10 @@ Motors connection table:
 
 |Motor|Position|Direction|Prop type|Motor wires|GPIO|
 |-|-|-|-|-|-|
-|Motor 0|Rear left|Counter-clockwise|B|Black & White|GPIO12 (*TDI*)|
+|Motor 0|Rear left|Counter-clockwise|B|Black & White|GPIO12 *(TDI)*|
-|Motor 1|Rear right|Clockwise|A|Blue & Red|GPIO13 (*TCK*)|
+|Motor 1|Rear right|Clockwise|A|Blue & Red|GPIO13 *(TCK)*|
-|Motor 2|Front right|Counter-clockwise|B|Black & White|GPIO14 (*TMS*)|
+|Motor 2|Front right|Counter-clockwise|B|Black & White|GPIO14 *(TMS)*|
-|Motor 3|Front left|Clockwise|A|Blue & Red|GPIO15 (*TD0*)|
+|Motor 3|Front left|Clockwise|A|Blue & Red|GPIO15 *(TD0)*|
 
 ## Motors tightening
 

docs/book/firmware.md

@@ -35,7 +35,7 @@
 
 ### Подсистема управления
 
-Состояние органов управления обрабатывается в функции `interpretControls()` и преобразуется в *команду управления*, которая включает следующее:
+Состояние органов управления обрабатывается в функции `interpretControls()` и преобразуется в **команду управления**, которая включает следующее:
 
 * `attitudeTarget` *(Quaternion)* — целевая ориентация дрона.
 * `ratesTarget` *(Vector)* — целевые угловые скорости, *рад/с*.

docs/book/geometry.md

@@ -110,7 +110,7 @@ float angle = Vector::angleBetween(a, b); // 1.57 (90 градусов)
 
 #### Скалярное произведение
 
-Скалярное произведение векторов (*dot product*) — это произведение длин двух векторов на косинус угла между ними. В математике оно обозначается знаком `·` или слитным написанием векторов. Интуитивно, результат скалярного произведения показывает, насколько два вектора *сонаправлены*.
+Скалярное произведение векторов *(dot product)* — это произведение длин двух векторов на косинус угла между ними. В математике оно обозначается знаком `·` или слитным написанием векторов. Интуитивно, результат скалярного произведения показывает, насколько два вектора *сонаправлены*.
 
 В Flix используется статический метод `Vector::dot()`:
 
@@ -124,7 +124,7 @@ float dotProduct = Vector::dot(a, b); // 32
 
 #### Векторное произведение
 
-Векторное произведение (*cross product*) позволяет найти вектор, перпендикулярный двум другим векторам. В математике оно обозначается знаком `×`, а в прошивке используется статический метод `Vector::cross()`:
+Векторное произведение *(cross product)* позволяет найти вектор, перпендикулярный двум другим векторам. В математике оно обозначается знаком `×`, а в прошивке используется статический метод `Vector::cross()`:
 
 ```cpp
 Vector a(1, 2, 3);
@@ -144,9 +144,9 @@ Vector crossProduct = Vector::cross(a, b); // -3, 6, -3
 
 В прошивке углы Эйлера сохраняются в обычный объект `Vector` (хоть и, строго говоря, не являются вектором):
 
-* Угол по крену (*roll*) — `vector.x`.
+* Угол по крену *(roll)* — `vector.x`.
-* Угол по тангажу (*pitch*) — `vector.y`.
+* Угол по тангажу *(pitch)* — `vector.y`.
-* Угол по рысканию (*yaw*) — `vector.z`.
+* Угол по рысканию *(yaw)* — `vector.z`.
 
 Особенности углов Эйлера:
 
@@ -162,8 +162,8 @@ Vector crossProduct = Vector::cross(a, b); // -3, 6, -3
 
 Помимо углов Эйлера, любую ориентацию в трехмерном пространстве можно представить в виде вращения вокруг некоторой оси на некоторый угол. В геометрии это доказывается, как **теорема вращения Эйлера**. В таком представлении ориентация задается двумя величинами:
 
-* **Ось вращения** (*axis*) — единичный вектор, определяющий ось вращения.
+* **Ось вращения** *(axis)* — единичный вектор, определяющий ось вращения.
-* **Угол поворота** (*angle* или *θ*) — угол, на который нужно повернуть объект вокруг этой оси.
+* **Угол поворота** *(angle* или *θ)* — угол, на который нужно повернуть объект вокруг этой оси.
 
 В Flix ось вращения задается объектом `Vector`, а угол поворота — числом типа `float` в радианах:
 
@@ -177,7 +177,7 @@ float angle = radians(45);
 
 ### Вектор вращения
 
-Если умножить вектор *axis* на угол поворота *θ*, то получится **вектор вращения** (*rotation vector*). Этот вектор играет важную роль в алгоритмах управления ориентацией летательного аппарата.
+Если умножить вектор *axis* на угол поворота *θ*, то получится **вектор вращения** *(rotation vector)*. Этот вектор играет важную роль в алгоритмах управления ориентацией летательного аппарата.
 
 Вектор вращения обладает замечательным свойством: если угловые скорости объекта (в собственной системе координат) в каждый момент времени совпадают с компонентами этого вектора, то за единичное время объект придет к заданной этим вектором ориентации. Это свойство позволяет использовать вектор вращения для управления ориентацией объекта посредством управления угловыми скоростями.
 
@@ -198,7 +198,7 @@ Vector rotation = radians(45) * Vector(1, 2, 3);
 	<a href="https://github.com/okalachev/flix/blob/master/flix/quaternion.h"><code>quaternion.h</code></a>.<br>
 </div>
 
-Вектор вращения удобен, но еще удобнее использовать **кватернион**. В Flix кватернионы задаются объектами `Quaternion` из библиотеки `quaternion.h`. Кватернион состоит из четырех значений: *w*, *x*, *y*, *z* и рассчитывается из вектора оси вращения (*axis*) и угла поворота (*θ*) по формуле:
+Вектор вращения удобен, но еще удобнее использовать **кватернион**. В Flix кватернионы задаются объектами `Quaternion` из библиотеки `quaternion.h`. Кватернион состоит из четырех значений: *w*, *x*, *y*, *z* и рассчитывается из вектора оси вращения *(axis)* и угла поворота *(θ)* по формуле:
 
 \\[ q = \left( \begin{array}{c} w \\\\ x \\\\ y \\\\ z \end{array} \right) = \left( \begin{array}{c} \cos\left(\frac{\theta}{2}\right) \\\\ axis\_x \cdot \sin\left(\frac{\theta}{2}\right) \\\\ axis\_y \cdot \sin\left(\frac{\theta}{2}\right) \\\\ axis\_z \cdot \sin\left(\frac{\theta}{2}\right) \end{array} \right) \\]
 

docs/book/gyro.md

@@ -87,13 +87,13 @@ Flix поддерживает следующие модели IMU:
 #include <FlixPeriph.h>
 #include <SPI.h>
 
-MPU9250 IMU(SPI);
+MPU9250 imu(SPI);
 
 void setup() {
 	Serial.begin(115200);
-	bool success = IMU.begin();
+	bool success = imu.begin();
 	if (!success) {
-		Serial.println("Failed to initialize IMU");
+		Serial.println("Failed to initialize the IMU");
 	}
 }
 ```
@@ -108,21 +108,21 @@ void setup() {
 #include <FlixPeriph.h>
 #include <SPI.h>
 
-MPU9250 IMU(SPI);
+MPU9250 imu(SPI);
 
 void setup() {
 	Serial.begin(115200);
-	bool success = IMU.begin();
+	bool success = imu.begin();
 	if (!success) {
-		Serial.println("Failed to initialize IMU");
+		Serial.println("Failed to initialize the IMU");
 	}
 }
 
 void loop() {
-	IMU.waitForData();
+	imu.waitForData();
 
 	float gx, gy, gz;
-	IMU.getGyro(gx, gy, gz);
+	imu.getGyro(gx, gy, gz);
 
 	Serial.printf("gx:%f gy:%f gz:%f\n", gx, gy, gz);
 	delay(50); // замедление вывода
@@ -135,36 +135,36 @@ void loop() {
 
 ## Конфигурация гироскопа
 
-В коде Flix настройка IMU происходит в функции `configureIMU`. В этой функции настраиваются три основных параметра гироскопа: диапазон измерений, частота сэмплов и частота LPF-фильтра.
+В коде Flix настройка IMU происходит в функции `configureIMU`. В этой функции настраиваются три основных параметра гироскопа: диапазон измерений, частота сэмплирования и частота LPF-фильтра.
 
-### Частота сэмплов
+### Частота сэмплирования
 
-Большинство IMU могут обновлять данные с разной частотой. В полетных контроллерах обычно используется частота обновления от 500 Гц до 8 кГц. Чем выше частота сэмплов, тем выше точность управления полетом, но и больше нагрузка на микроконтроллер.
+Большинство IMU могут обновлять данные с разной частотой. В полетных контроллерах обычно используется частота обновления от 500 Гц до 8 кГц. Чем выше частота, тем выше точность управления полетом, но и тем больше нагрузка на микроконтроллер.
 
-Частота сэмплов устанавливается методом `setSampleRate()`. В Flix используется частота 1 кГц:
+Частота сэмплирования устанавливается методом `setSampleRate()`. В Flix используется частота 1 кГц:
 
 ```cpp
 IMU.setRate(IMU.RATE_1KHZ_APPROX);
 ```
 
-Поскольку не все поддерживаемые IMU могут работать строго на частоте 1 кГц, в библиотеке FlixPeriph существует возможность приближенной настройки частоты сэмплов. Например, у IMU ICM-20948 при такой настройке реальная частота сэмплирования будет равна 1125 Гц.
+Поскольку не все поддерживаемые IMU могут работать строго на частоте 1 кГц, в библиотеке FlixPeriph существует возможность приближенной настройки частоты сэмплирования. Например, у IMU ICM-20948 при такой настройке реальная частота сэмплирования будет равна 1125 Гц.
 
 Другие доступные для установки в библиотеке FlixPeriph частоты сэмплирования:
 
-* `RATE_MIN` — минимальная частота сэмплов для конкретного IMU.
+* `RATE_MIN` — минимальная частота для конкретного IMU.
 * `RATE_50HZ_APPROX` — значение, близкое к 50 Гц.
 * `RATE_1KHZ_APPROX` — значение, близкое к 1 кГц.
 * `RATE_8KHZ_APPROX` — значение, близкое к 8 кГц.
-* `RATE_MAX` — максимальная частота сэмплов для конкретного IMU.
+* `RATE_MAX` — максимальная частота для конкретного IMU.
 
 #### Диапазон измерений
 
-Большинство MEMS-гироскопов поддерживают несколько диапазонов измерений угловой скорости. Главное преимущество выбора меньшего диапазона — бо́льшая чувствительность. В полетных контроллерах обычно выбирается максимальный диапазон измерений от –2000 до 2000 градусов в секунду, чтобы обеспечить возможность динамичных маневров.
+Большинство MEMS-гироскопов поддерживают несколько диапазонов измерений угловой скорости. Главное преимущество выбора меньшего диапазона — бо́льшая чувствительность. В полетных контроллерах обычно выбирается максимальный диапазон измерений от –2000 до 2000 градусов в секунду, чтобы обеспечить возможность быстрых маневров.
 
 В библиотеке FlixPeriph диапазон измерений гироскопа устанавливается методом `setGyroRange()`:
 
 ```cpp
-IMU.setGyroRange(IMU.GYRO_RANGE_2000DPS);
+imu.setGyroRange(imu.GYRO_RANGE_2000DPS);
 ```
 
 ### LPF-фильтр
@@ -172,16 +172,16 @@ IMU.setGyroRange(IMU.GYRO_RANGE_2000DPS);
 IMU InvenSense могут фильтровать измерения на аппаратном уровне при помощи фильтра нижних частот (LPF). Flix реализует собственный фильтр для гироскопа, чтобы иметь больше гибкости при поддержке разных IMU. Поэтому для встроенного LPF устанавливается максимальная частота среза:
 
 ```cpp
-IMU.setDLPF(IMU.DLPF_MAX);
+imu.setDLPF(imu.DLPF_MAX);
 ```
 
 ## Калибровка гироскопа
 
-Как и любое измерительное устройство, гироскоп вносит искажения в измерения. Наиболее простая модель этих искажений делит их на статические смещения (*bias*) и случайный шум (*noise*):
+Как и любое измерительное устройство, гироскоп вносит искажения в измерения. Наиболее простая модель этих искажений делит их на статические смещения *(bias)* и случайный шум *(noise)*:
 
 \\[ gyro_{xyz}=rates_{xyz}+bias_{xyz}+noise \\]
 
-Для качественной работы подсистемы оценки ориентации и управления дроном необходимо оценить *bias* гироскопа и учесть его в вычислениях. Для этого при запуске программы производится калибровка гироскопа, которая реализована в функции `calibrateGyro()`. Эта функция считывает данные с гироскопа в состоянии покоя 1000 раз и усредняет их. Полученные значения считаются *bias* гироскопа и в дальнейшем вычитаются из измерений.
+Для точной работы подсистемы оценки ориентации и управления дроном необходимо оценить *bias* гироскопа и учесть его в вычислениях. Для этого при запуске программы производится калибровка гироскопа, которая реализована в функции `calibrateGyro()`. Эта функция считывает данные с гироскопа в состоянии покоя 1000 раз и усредняет их. Полученные значения считаются *bias* гироскопа и в дальнейшем вычитаются из измерений.
 
 Программа для вывода данных с гироскопа с калибровкой:
 
@@ -189,23 +189,23 @@ IMU.setDLPF(IMU.DLPF_MAX);
 #include <FlixPeriph.h>
 #include <SPI.h>
 
-MPU9250 IMU(SPI);
+MPU9250 imu(SPI);
 
 float gyroBiasX, gyroBiasY, gyroBiasZ; // bias гироскопа
 
 void setup() {
 	Serial.begin(115200);
-	bool success = IMU.begin();
+	bool success = imu.begin();
 	if (!success) {
-		Serial.println("Failed to initialize IMU");
+		Serial.println("Failed to initialize the IMU");
 	}
 	calibrateGyro();
 }
 
 void loop() {
 	float gx, gy, gz;
-	IMU.waitForData();
+	imu.waitForData();
-	IMU.getGyro(gx, gy, gz);
+	imu.getGyro(gx, gy, gz);
 
 	// Устранение bias гироскопа
 	gx -= gyroBiasX;
@@ -226,9 +226,9 @@ void calibrateGyro() {
 
 	// Получение 1000 измерений гироскопа
 	for (int i = 0; i < samples; i++) {
-		IMU.waitForData();
+		imu.waitForData();
 		float gx, gy, gz;
-		IMU.getGyro(gx, gy, gz);
+		imu.getGyro(gx, gy, gz);
 		gyroBiasX += gx;
 		gyroBiasY += gy;
 		gyroBiasZ += gz;

docs/firmware.md

@@ -38,13 +38,13 @@ Utility files:
 
 ### Control subsystem
 
-Pilot inputs are interpreted in `interpretControls()`, and then converted to the *control command*, which consists of the following:
+Pilot inputs are interpreted in `interpretControls()`, and then converted to the **control command**, which consists of the following:
 
 * `attitudeTarget` *(Quaternion)* — target attitude of the drone.
 * `ratesTarget` *(Vector)* — target angular rates, *rad/s*.
-* `ratesExtra` *(Vector)* — additional (feed-forward) angular rates , used for yaw rate control in STAB mode, *rad/s*.
+* `ratesExtra` *(Vector)* — additional (feed-forward) angular rates, used for yaw rate control in STAB mode, *rad/s*.
 * `torqueTarget` *(Vector)* — target torque, range [-1, 1].
-* `thrustTarget` *(float)* — collective thrust target, range [0, 1].
+* `thrustTarget` *(float)* — collective motor thrust target, range [0, 1].
 
 Control command is handled in `controlAttitude()`, `controlRates()`, `controlTorque()` functions. Each function may be skipped if the corresponding control target is set to `NAN`.
 
@@ -62,6 +62,40 @@ print("Test value: %.2f\n", testValue);
 
 In order to add a console command, modify the `doCommand()` function in `cli.ino` file.
 
+> [!IMPORTANT]
+> Avoid using delays in in-flight commands, it will **crash** the drone! (The design is one-threaded.)
+>
+> For on-the-ground commands, use `pause()` function, instead of `delay()`. This function allows to pause in a way that MAVLink connection will continue working.
+
+### Parameter subsystem
+
+Parameters subsystem (`parameters.ino`) uses standard [Preferences.h](https://docs.espressif.com/projects/arduino-esp32/en/latest/tutorials/preferences.html) ESP32 library to store parameters in non-volatile memory. Each parameter is a regular global variable, which is registered in the `parameters` array.
+
+To add a new parameter:
+
+1. Define a global variable for the parameter, two types are supported: `float` and `int`.
+2. Add an entry to the `parameters` array, with the parameter name, a pointer to the variable, and optionally a callback function to call when the parameter is changed.
+3. Everything else will be handled automatically.
+
+See examples of adding new parameters in commits: [c434107](https://github.com/okalachev/flix/commit/c434107), [a687303](https://github.com/okalachev/flix/commit/a687303).
+
+## Adding a subsystem
+
+To add a new subsystem:
+
+1. Create a new `*.ino` file for your subsystem.
+2. Define setup and loop functions for the subsystem, for example `setupMySubsystem()` and `loopMySubsystem()`.
+3. Use `Rate` class if you need to limit the loop frequency, for example:
+
+    ```cpp
+    Rate mySubsystemRate(100); // 100 Hz
+
+    void loopMySubsystem() {
+    	if (!mySubsystemRate) return;
+    	// Do something...
+    }
+4. Add setup and loop calls in to `setup()` and `loop()` functions in `flix.ino`.
+
 ## Building the firmware
 
 See build instructions in [usage.md](usage.md).

docs/img/flix.svg

@@ -0,0 +1,38 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 734.86 378.46">
+  <defs>
+    <style>
+      .a {
+        fill: none;
+        stroke: #d5d5d5;
+        stroke-miterlimit: 10;
+        stroke-width: 31px;
+      }
+
+      .b {
+        fill: #c1c1c1;
+      }
+
+      .c {
+        fill: #ff9400;
+      }
+
+      .d {
+        fill: #d5d5d5;
+      }
+    </style>
+  </defs>
+  <g>
+    <g>
+      <line class="a" x1="448.78" y1="294.23" x2="648.77" y2="93.24"/>
+      <line class="a" x1="449.78" y1="94.24" x2="649.77" y2="295.23"/>
+      <circle class="b" cx="549.27" cy="193.73" r="41.5"/>
+      <circle class="c" cx="449.35" cy="93.74" r="77.95"/>
+      <circle class="c" cx="648.89" cy="93.53" r="77.95"/>
+      <circle class="c" cx="647.89" cy="294.51" r="77.95"/>
+      <circle class="c" cx="448.9" cy="294.51" r="77.95"/>
+    </g>
+    <path class="d" d="M8,161.93q0-17.85,22.36-17.85h4.81V100.57Q35.17,8.49,131.23,8h1q36.87,0,47.31,7.48L181,17.41l1,2.41V50q0,12.32-5.82,12.31-2.43,0-7.4-4.64t-14.19-9a48.63,48.63,0,0,0-21.22-4.41q-12,0-19.17,3.5a18.85,18.85,0,0,0-9.82,10.62,67.35,67.35,0,0,0-3.52,12.06,82.52,82.52,0,0,0-.85,13.39v60.32h27.28q10.86,0,16.05,5.43a17.52,17.52,0,0,1,5.19,12.42,22.5,22.5,0,0,1-1.21,7.36q-1.22,3.51-6.64,7.24t-14.36,3.74H101.64V344.82a56,56,0,0,1-.61,9.65,37.8,37.8,0,0,1-2.56,7.6,11.83,11.83,0,0,1-6.94,6.4q-5,1.93-13.51,1.93H57.08q-10.47,0-15.7-4.71t-5.73-8.44a77.31,77.31,0,0,1-.48-9.53V180.27H29.4Q8,180.27,8,161.93Z"/>
+    <path class="d" d="M201.21,348.2V37q0-23.16,20.86-23.4h22.81q22.8,0,22.8,22.44V346.27a68.92,68.92,0,0,1-.49,9.41,22.59,22.59,0,0,1-2.42,7.12,11.48,11.48,0,0,1-6.67,5.43,47.78,47.78,0,0,1-12.74,2.17H225q-11.4,0-17.58-4.47T201.21,348.2Z"/>
+    <path class="d" d="M284.9,61.08V36.47a40.39,40.39,0,0,1,1.7-12.91,11.36,11.36,0,0,1,6.18-7,25.27,25.27,0,0,1,6.68-2.3c1.45-.15,4-.4,7.76-.72h25.23q10.43,0,16.73,4.7t6.31,18.22V62.05a27.94,27.94,0,0,1-.85,7.11,23,23,0,0,1-2.06,5.43,20,20,0,0,1-2.91,4,10,10,0,0,1-3.52,2.54c-1.21.48-2.54,1-4,1.44a11.53,11.53,0,0,1-3.4.73,13.71,13.71,0,0,0-3.15.48H307.7q-10.43,0-16.61-4.7T284.9,61.08Zm1.94,284.71V166.28q0-22.2,21.83-22.2h20.38q10.92,0,16.62,4t6.67,8.45a60.47,60.47,0,0,1,1,12.18V348.2q0,22.2-21.83,22.2H308.67q-10.43,0-15.64-4.95t-5.7-8.81A90.93,90.93,0,0,1,286.84,345.79Z"/>
+  </g>
+</svg>

docs/troubleshooting.md

@@ -4,7 +4,7 @@
 
 Do the following:
 
-* **Check ESP32 core is installed**. Check if the version matches the one used in the [tutorial](usage.md#firmware).
+* **Check ESP32 core is installed**. Check if the version matches the one used in the [tutorial](usage.md#building-the-firmware).
 * **Check libraries**. Install all the required libraries from the tutorial. Make sure there are no MPU9250 or other peripherals libraries that may conflict with the ones used in the tutorial.
 * **Check the chosen board**. The correct board to choose in Arduino IDE for ESP32 Mini is *WEMOS D1 MINI ESP32*.
 
@@ -12,20 +12,25 @@ Do the following:
 
 Do the following:
 
-* **Check the battery voltage**. Use a multimeter to measure the battery voltage. It should be in range of 3.7-4.2 V.
+* **Check the battery voltage**. Use a multimeter to measure the battery voltage. The fully charged battery should have about 4.2V.
-* **Check if there are some startup errors**. Connect the ESP32 to the computer and check the Serial Monitor output. Use the Reset button to make sure you see the whole ESP32 output.
+* **Check the battery you use has enough discharge current**. The battery should be able to provide 15A of current. So the C-rating for a 1000 mAh battery should be at least 15C (higher is better).
+* **Check if there are some startup errors**. Connect the ESP32 to the computer and check the Serial Monitor output. Use the Reset button or `reboot` command to see the whole startup output.
 * **Check the baudrate is correct**. If you see garbage characters in the Serial Monitor, make sure the baudrate is set to 115200.
-* **Make sure correct IMU model is chosen**. If using ICM-20948/MPU-6050 board, change `MPU9250` to `ICM20948`/`MPU6050` in the `imu.ino` file.
+* **Check if the console is working**. Perform `help` command in Serial Monitor. You should see the list of available commands. You can also access the console using QGroundControl *(Vehicle Setup* ⇒ *Analyze Tools* ⇒ *MAVLink Console)*.
-* **Check if the CLI is working**. Perform `help` command in Serial Monitor. You should see the list of available commands. You can also access the CLI using QGroundControl (*Vehicle Setup* ⇒ *Analyze Tools* ⇒ *MAVLink Console*).
 * **Configure QGroundControl correctly before connecting to the drone** if you use it to control the drone. Go to the settings and enable *Virtual Joystick*. *Auto-Center Throttle* setting **should be disabled**.
 * **If QGroundControl doesn't connect**, you might need to disable the firewall and/or VPN on your computer.
+* **Make sure correct IMU model is chosen**. If using ICM-20948/MPU-6050 board, change `MPU9250` to `ICM20948`/`MPU6050` in the `imu.ino` file.
 * **Check the IMU is working**. Perform `imu` command and check its output:
   * The `status` field should be `OK`.
   * The `rate` field should be about 1000 (Hz).
   * The `accel` and `gyro` fields should change as you move the drone.
+* **Check the IMU orientation is set correctly**. If the attitude estimation is rotated, set the correct IMU orientation as described in the [tutorial](usage.md#define-imu-orientation).
 * **Calibrate the accelerometer.** if is wasn't done before. Type `ca` command in Serial Monitor and follow the instructions.
-* **Check the attitude estimation**. Connect to the drone using QGroundControl. Rotate the drone in different orientations and check if the attitude estimation shown in QGroundControl is correct.
+* **Check the attitude estimation**. Connect to the drone using QGroundControl. Rotate the drone in different orientations and check if the attitude estimation is shown exactly as on the video below:
-* **Check the IMU orientation is set correctly**. If the attitude estimation is rotated, make sure `rotateIMU` function is defined correctly in `imu.ino` file.
+
+  <a href="https://youtu.be/yVRN23-GISU"><img width=200 src="https://i3.ytimg.com/vi/yVRN23-GISU/maxresdefault.jpg"></a>
+
+* **Check the IMU output**. Connect to the drone using QGroundControl on your computer. Go to the *Analyze* tab, *MAVLINK Inspector*. Plot the data from the `SCALED_IMU` message. The gyroscope and accelerometer data should change according to the drone movement.
 * **Check the motors type**. Motors with exact 3.7V voltage are needed, not ranged working voltage (3.7V — 6V).
 * **Check the motors**. Perform the following commands using Serial Monitor:
   * `mfr` — should rotate front right motor (counter-clockwise).
@@ -33,7 +38,10 @@ Do the following:
   * `mrl` — should rotate rear left motor (counter-clockwise).
   * `mrr` — should rotate rear right motor (clockwise).
 * **Check the propeller directions are correct**. Make sure your propeller types (A or B) are installed as on the picture:
+
   <img src="img/user/peter_ukhov-2/1.jpg" width="200">
-* **Check the remote control**. Using `rc` command, check the control values reflect your sticks movement. All the controls should change between -1 and 1, and throttle between 0 and 1.
+
-* If using SBUS receiver, **calibrate the RC**. Type `cr` command in Serial Monitor and follow the instructions.
+* **If using an SBUS receiver**:
-* **Check the IMU output using QGroundControl**. Connect to the drone using QGroundControl on your computer. Go to the *Analyze* tab, *MAVLINK Inspector*. Plot the data from the `SCALED_IMU` message. The gyroscope and accelerometer data should change according to the drone movement.
+  * **Define the used GPIO pin** in `RC_RX_PIN` parameter.
+  * **Calibrate the RC** using `cr` command in the console.
+  * **Check the controls** using `rc` command. All the controls should change between -1 and 1, and the throttle between 0 and 1.

docs/usage.md

@@ -12,7 +12,7 @@ Beginners can [download the source code as a ZIP archive](https://github.com/oka
 
 ## Building the firmware
 
-You can build and upload the firmware using either **Arduino IDE** (easier for beginners) or a **command line**.
+You can build and upload the firmware using either **Arduino IDE** (easier for beginners) or **command line**.
 
 ### Arduino IDE (Windows, Linux, macOS)
 
@@ -20,10 +20,10 @@ You can build and upload the firmware using either **Arduino IDE** (easier for b
 
 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.
+3. Install ESP32 core, version 3.3.6. 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.
+   * `MAVLink`, version 2.0.25.
 5. Open the `flix/flix.ino` sketch from downloaded firmware sources in Arduino IDE.
 6. Connect your ESP32 board to the computer and choose correct board type in Arduino IDE (*WEMOS D1 MINI ESP32* for ESP32 Mini) and the port.
 7. [Build and upload](https://docs.arduino.cc/software/ide-v2/tutorials/getting-started/ide-v2-uploading-a-sketch) the firmware using Arduino IDE.
@@ -73,14 +73,6 @@ ICM20948 imu(SPI);  // For ICM-20948
 MPU6050 imu(Wire);  // For MPU-6050
 ```
 
-### Setup the IMU orientation
-
-The IMU orientation is defined in `rotateIMU` function in the `imu.ino` file. Change it so it converts the IMU axes to the drone's axes correctly. **Drone axes are X forward, Y left, Z up**:
-
-<img src="img/drone-axes.svg" width="200">
-
-See various [IMU boards axes orientations table](https://github.com/okalachev/flixperiph/?tab=readme-ov-file#imu-axes-orientation) to help you set up the correct orientation.
-
 ### Connect using QGroundControl
 
 QGroundControl is a ground control station software that can be used to monitor and control the drone.
@@ -88,7 +80,7 @@ QGroundControl is a ground control station software that can be used to monitor
 1. Install mobile or desktop version of [QGroundControl](https://docs.qgroundcontrol.com/master/en/qgc-user-guide/getting_started/download_and_install.html).
 2. Power up the drone.
 3. Connect your computer or smartphone to the appeared `flix` Wi-Fi network (password: `flixwifi`).
-4. Launch QGroundControl app. It should connect and begin showing the drone's telemetry automatically
+4. Launch QGroundControl app. It should connect and begin showing the drone's telemetry automatically.
 
 ### Access console
 
@@ -104,11 +96,37 @@ To access the console using QGroundControl:
 
 1. Connect to the drone using QGroundControl app.
 2. Go to the QGroundControl menu ⇒ *Vehicle Setup* ⇒ *Analyze Tools* ⇒ *MAVLink Console*.
-   <img src="img/cli.png" width="400">
+
+<img src="img/cli.png" width="400">
 
 > [!TIP]
 > Use `help` command to see the list of available commands.
 
+### Access parameters
+
+The drone is configured using parameters. To access and modify them, go to the QGroundControl menu ⇒ *Vehicle Setup* ⇒ *Parameters*:
+
+<img src="img/parameters.png" width="400">
+
+You can also work with parameters using `p` command in the console. Parameter names are case-insensitive.
+
+### Define IMU orientation
+
+The IMU orientation (relative to the drone's axes) is defined using the parameters: `IMU_ROT_ROLL`, `IMU_ROT_PITCH`, and `IMU_ROT_YAW`.
+
+The drone has *X* axis pointing forward, *Y* axis pointing left, and *Z* axis pointing up, and the supported IMU boards have *X* axis pointing to the mounting holes side and *Z* axis pointing up from the component side:
+
+<img src="img/imu-axes.png" width="200">
+
+Use the following table to set the parameters for common IMU orientations:
+
+|Orientation|Parameters|Orientation|Parameters|
+|:-:|-|-|-|
+|<img src="img/imu-rot-3.png" width="180">|`IMU_ROT_ROLL` = 0<br>`IMU_ROT_PITCH` = 0<br>`IMU_ROT_YAW` = 0    |<img src="img/imu-rot-7.png" width="180">|`IMU_ROT_ROLL` = 3.142<br>`IMU_ROT_PITCH` = 0<br>`IMU_ROT_YAW` = 0|
+|<img src="img/imu-rot-2.png" width="180">|`IMU_ROT_ROLL` = 0<br>`IMU_ROT_PITCH` = 0<br>`IMU_ROT_YAW` = -1.571|<img src="img/imu-rot-6.png" width="180">|`IMU_ROT_ROLL` = 3.142<br>`IMU_ROT_PITCH` = 0<br>`IMU_ROT_YAW` = -1.571|
+|<img src="img/imu-rot-1.png" width="180">|`IMU_ROT_ROLL` = 0<br>`IMU_ROT_PITCH` = 0<br>`IMU_ROT_YAW` = 3.142|<img src="img/imu-rot-5.png" width="180">|`IMU_ROT_ROLL` = 3.142<br>`IMU_ROT_PITCH` = 0<br>`IMU_ROT_YAW` = 3.142|
+|<img src="img/imu-rot-4.png" width="180"><br>☑️ **Default**|<br>`IMU_ROT_ROLL` = 0<br>`IMU_ROT_PITCH` = 0<br>`IMU_ROT_YAW` = 1.571|<img src="img/imu-rot-8.png" width="180">|`IMU_ROT_ROLL` = 3.142<br>`IMU_ROT_PITCH` = 0<br>`IMU_ROT_YAW` = 1.571|
+
 ### Calibrate accelerometer
 
 Before flight you need to calibrate the accelerometer:
@@ -116,25 +134,54 @@ Before flight you need to calibrate the accelerometer:
 1. Access the console using QGroundControl (recommended) or Serial Monitor.
 2. Type `ca` command there and follow the instructions.
 
-### Check everything works
+### Setup motors
 
-1. Check the IMU is working: perform `imu` command and check its output:
+If using non-default motor pins, set the pin numbers using the parameters: `MOTOR_PIN_FL`, `MOTOR_PIN_FR`, `MOTOR_PIN_RL`, `MOTOR_PIN_RR` (front-left, front-right, rear-left, rear-right respectively).
+
+Certain ESP32 models (such as ESP32-S3 and ESP32-C3) support a lower maximum PWM frequency; on these boards the parameter `MOT_PWM_FREQ` should be set to 38000 Hz.
+
+If using brushless motors and ESCs:
+
+1. Set the appropriate PWM using the parameters: `MOT_PWM_STOP`, `MOT_PWM_MIN`, and `MOT_PWM_MAX` (1000, 1000, and 2000 is typical).
+2. Decrease the PWM frequency using the `MOT_PWM_FREQ` parameter (400 is typical).
+
+> [!CAUTION]
+> **Remove the props when configuring the motors!** If improperly configured, you may not be able to stop them.
+
+### Battery voltage monitoring
+
+ESP32 ADC can measure only up to 3.3 V, so you need to use a voltage divider to monitor the battery voltage. To enable voltage measurement, set the following parameters:
+
+1. `PWR_VOLT_PIN` — GPIO pin number where the voltage divider is connected (*-1* to disable).
+2. `PWR_VOLT_SCALE` — voltage divider coefficient (*2* for two equal resistors).
+
+After this setup, you should see the battery voltage in QGroundControl top panel or using `pw` command in the console.
+
+### Important: check everything works
+
+1. Check the IMU is working: perform `imu` command in the console and check the output:
 
    * The `status` field should be `OK`.
    * The `rate` field should be about 1000 (Hz).
    * The `accel` and `gyro` fields should change as you move the drone.
+   * The `accel bias` and `accel scale` fields should contain calibration parameters (not zeros and ones).
+   * The `gyro bias` field should contain estimated gyro bias (not zeros).
    * The `landed` field should be `1` when the drone is still on the ground and `0` when you lift it up.
 
-2. Check the attitude estimation: connect to the drone using QGroundControl, rotate the drone in different orientations and check if the attitude estimation shown in QGroundControl is correct. Attitude indicator in QGroundControl is shown below:
+2. Check the attitude estimation: connect to the drone using QGroundControl, rotate the drone in different orientations and check if the attitude estimation shown in QGroundControl is correct. Compare your attitude indicator (in the *large vertical* mode) to the video:
 
-   <img src="img/qgc-attitude.png" height="200">
+   <a href="https://youtu.be/yVRN23-GISU"><img width=300 src="https://i3.ytimg.com/vi/yVRN23-GISU/maxresdefault.jpg"></a>
 
-3. Perform motor tests in the console. Use the following commands **— remove the propellers before running the tests!**
+3. Perform motor tests. Use the following commands **— remove the propellers before running the tests!**
 
-   * `mfr` — should rotate front right motor (counter-clockwise).
+   * `mfr` — rotate front right motor (counter-clockwise).
-   * `mfl` — should rotate front left motor (clockwise).
+   * `mfl` — rotate front left motor (clockwise).
-   * `mrl` — should rotate rear left motor (counter-clockwise).
+   * `mrl` — rotate rear left motor (counter-clockwise).
-   * `mrr` — should rotate rear right motor (clockwise).
+   * `mrr` — rotate rear right motor (clockwise).
+
+   Make sure rotation directions and propeller types match the following diagram:
+
+   <img src="img/motors.svg" width=200>
 
 > [!WARNING]
 > Never run the motors when powering the drone from USB, always use the battery for that.
@@ -143,7 +190,19 @@ Before flight you need to calibrate the accelerometer:
 
 There are several ways to control the drone's flight: using **smartphone** (Wi-Fi), using **SBUS remote control**, or using **USB remote control** (Wi-Fi).
 
-### Control with smartphone
+### Control with a smartphone
+
+#### Using Mavlink Joystick app (Android)
+
+<img src="https://github.com/goldarte/mavlink-joystick/blob/master/app_screen.png?raw=true" width="400">
+
+1. Download and install [Mavlink Joystick app](https://github.com/goldarte/mavlink-joystick/releases/latest).
+2. Power the drone using the battery.
+3. Connect your smartphone to the appeared `flix` Wi-Fi network (password: `flixwifi`).
+4. Open Mavlink Joystick app. It should connect and begin showing the drone's telemetry automatically.
+5. Use the virtual joystick to fly the drone!
+
+#### Using QGroundControl app
 
 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.
@@ -153,17 +212,19 @@ There are several ways to control the drone's flight: using **smartphone** (Wi-F
 6. Use the virtual joystick to fly the drone!
 
 > [!TIP]
-> Decrease `CNT_TILT_MAX` parameter when flying using the smartphone to make the controls less sensitive.
+> Decrease `CTL_TILT_MAX` parameter when flying using the smartphone to make the controls less sensitive.
 
-### Control with remote control
+### Control with a remote control
 
-Before using remote SBUS-connected remote control, you need to calibrate it:
+If using SBUS-connected remote control you need to enable SBUS and calibrate it:
 
-1. Access the console using QGroundControl (recommended) or Serial Monitor.
+1. Connect to the drone using QGroundControl.
-2. Type `cr` command and follow the instructions.
+2. In parameters, set the `RC_RX_PIN` parameter to the GPIO pin number where the SBUS signal is connected, for example: 4. Negative value disables SBUS.
-3. Use the remote control to fly the drone!
+3. Check if the receiver is working using `rc` command in the console.
+4. Open the console, type `cr` command and follow the instructions to calibrate the remote control.
+5. Use the remote control to fly the drone!
 
-### Control with USB remote control
+### Control with a USB remote control
 
 If your drone doesn't have RC receiver installed, you can use USB remote control and QGroundControl app to fly it.
 
@@ -198,11 +259,11 @@ When finished flying, **disarm** the drone, moving the left stick to the bottom
 
 ### Flight modes
 
-Flight mode is changed using mode switch on the remote control or using the command line.
+Flight mode is changed using mode switch on the remote control (if configured) or using the console commands. The main flight mode is *STAB*. In order to change modes using SBUS remote control, set the parameters: `CTL_FLT_MODE_0`, `CTL_FLT_MODE_1`, and `CTL_FLT_MODE_2` to required mode numbers (0 for *RAW*, 1 for *ACRO*, 2 for *STAB*, 3 for *AUTO*).
 
 #### STAB
 
-The default mode is *STAB*. In this mode, the drone stabilizes its attitude (orientation). The left stick controls throttle and yaw rate, the right stick controls pitch and roll angles.
+In this mode, the drone stabilizes its attitude (orientation). The left stick controls throttle and yaw rate, the right stick controls pitch and roll angles.
 
 > [!IMPORTANT]
 > The drone doesn't stabilize its position, so slight drift is possible. The pilot should compensate it manually.
@@ -211,25 +272,81 @@ The default mode is *STAB*. In this mode, the drone stabilizes its attitude (ori
 
 In this mode, the pilot controls the angular rates. This control method is difficult to fly and mostly used in FPV racing.
 
-#### MANUAL
+#### RAW
 
-Manual mode disables all the stabilization, and the pilot inputs are passed directly to the motors. This mode is intended for testing and demonstration purposes only, and basically the drone **cannot fly in this mode**.
+*RAW* mode disables all the stabilization, and the pilot inputs are mixed directly to the motors. The IMU sensor is not involved. This mode is intended for testing and demonstration purposes only, and basically the drone **cannot fly in this mode**.
 
 #### AUTO
 
-In this mode, the pilot inputs are ignored (except the mode switch, if configured). The drone can be controlled using [pyflix](../tools/pyflix/) Python library, or by modifying the firmware to implement the needed autonomous behavior.
+In this mode, the pilot inputs are ignored (except the mode switch). The drone can be controlled using [pyflix](../tools/pyflix/) Python library, or by modifying the firmware to implement the needed behavior.
 
-If the pilot moves the control sticks, the drone will switch back to *STAB* mode.
+If the pilot moves the control sticks and mode switch is not configured, the drone will switch back to *STAB* mode.
 
-## Adjusting parameters
+## Wi-Fi configuration
 
-You can adjust some of the drone's parameters (include PID coefficients) in QGroundControl. In order to do that, go to the QGroundControl menu ⇒ *Vehicle Setup* ⇒ *Parameters*.
+You can configure the Wi-Fi using parameters and console commands.
 
-<img src="img/parameters.png" width="400">
+The Wi-Fi mode is chosen using `WIFI_MODE` parameter in QGroundControl or in the console:
+
+* `0` — Wi-Fi is disabled.
+* `1` — Access Point mode *(AP)* — the drone creates a Wi-Fi network.
+* `2` — Client mode *(STA)* — the drone connects to an existing Wi-Fi network (may cause additional delays, so generally not recommended).
+* `3` — ESP-NOW mode — the drone uses ESP-NOW protocol for communication.
+
+The SSID and password are configured using the `ap` and `sta` console commands:
+
+```
+ap <ssid> <password>
+sta <ssid> <password>
+```
+
+Example of configuring the Access Point mode:
+
+```
+ap my-flix-ssid mypassword123
+p WIFI_MODE 1
+```
+
+Disabling Wi-Fi:
+
+```
+p WIFI_MODE 0
+```
+
+### Using ESP-NOW
+
+[ESP-NOW](https://docs.espressif.com/projects/esp-idf/en/stable/esp32/api-reference/network/esp_now.html) is a low level wireless communication protocol. It can provide lower latency, better reliability, and longer range than Wi-Fi. However, it requires a second ESP32 board to be used as a proxy for the computer.
+
+<img src="img/espnow-connection.jpg" width="600">
+
+To setup ESP-NOW communication:
+
+1. Flash the second ESP32 board with ESP-NOW proxy sketch: [`tools/espnow-proxy/espnow-proxy.ino`](../tools/espnow-proxy/espnow-proxy.ino). Use Arduino IDE or command line: `make upload_proxy`.
+
+2. Open Serial Monitor or use `make monitor` command. The ESP32 will print its MAC address and generated encryption key, for example:
+
+   ```
+   espnow 7a:c8:e3:eb:bf:e9 &PiuSysxP9+$L&5E
+   ```
+
+   Run this line as a console command on each drone you want to bind to this proxy board.
+
+3. Set the `WIFI_MODE` parameter to `3` on the drone:
+
+   ```
+   p WIFI_MODE 3
+   ```
+
+4. Go to the QGroundControl menu ⇒ *Application Settings* ⇒ *Comm Links*, add new link with the following settings:
+   * Name: ESP32.
+   * Type: Serial.
+   * Serial Port: choose the port of the proxy ESP32 board, e. g. `/dev/cu.usbserial-0001`.
+   * Baud Rate: 115200.
+5. Click *Save*. QGroundControl should connect to the drone using ESP-NOW and begin showing the telemetry.
 
 ## Flight log
 
-After the flight, you can download the flight log for analysis wirelessly. Use the following for that:
+After the flight, you can download the flight log for analysis wirelessly. Use the following command on your computer for that:
 
 ```bash
 make log

docs/user.md

@@ -4,12 +4,110 @@ This page contains user-built drones based on the Flix project. Publish your pro
 
 ---
 
+Author: [Ina Tix](https://t.me/ina_tix).<br>
+Description: XR2981 based DC-DC converter, ELRS MINI 2.4GHz RX SX1280 receiver (SBUS interface), Radiomaster TX12 remote control.<br>
+[Flight validation](https://drive.google.com/file/d/1yqkKNuz4R_yxGqUNQxVpixJbXqEEcUSj/view?usp=share_link).
+
+<img src="img/user/ina_tix/1.jpg" height=200> <img src="img/user/ina_tix/2.jpg" height=200> <img src="img/user/ina_tix/3.jpg" height=200>
+
+---
+
+Author: Oleg Kalachev.<br>
+Description: the first attempt on making an official PCB based Flix drone (Flix2 board). The IMU is not working on this version, so an external MPU-6050 board was used, therefore considered as **Flix version 1.5**.<br>
+[Flight video](https://drive.google.com/file/d/1R7tuUsFmPY0CGcOCFfMFaCp9kR49K3bl/view?usp=sharing).
+
+<img src="img/flix1.5.jpg" width=300>
+
+---
+
+Author: [FanBy0ru](https://https://github.com/FanBy0ru).<br>
+Description: custom 3D-printed frame.<br>
+Frame STLs and flight validation: https://cults3d.com/en/3d-model/gadget/armature-pour-flix-drone.
+
+<img src="img/user/fanby0ru/1.jpg" height=200> <img src="img/user/fanby0ru/2.jpg" height=200>
+
+---
+
+Author: Ivan44 Phalko.<br>
+Description: custom PCB, cusom test bench.<br>
+[Flight validation](https://drive.google.com/file/d/17DNDJ1gPmCmDRAwjedCbJ9RXAyqMqqcX/view?usp=sharing).
+
+<img src="img/user/phalko/1.jpg" height=200> <img src="img/user/phalko/2.jpg" height=200> <img src="img/user/phalko/3.jpg" height=200>
+
+---
+
+Author: **Arkadiy "Arky" Matsekh**, Foucault Dynamics, Gold Coast, Australia.<br>
+The drone was built for the University of Queensland industry-led Master's capstone project.
+
+**Flight video:**
+
+<a href="https://drive.google.com/file/d/1NNYSVXBY-w0JjCo07D8-PgnVq3ca9plj/view?usp=sharing"><img height=300 src="img/user/arkymatsekh/video.jpg"></a>
+
+<img src="img/user/arkymatsekh/1.jpg" height=150> <img src="img/user/arkymatsekh/2.jpg" height=150> <img src="img/user/arkymatsekh/3.jpg" height=150>
+
+---
+
+Author: [goldarte](https://t.me/goldarte).<br>
+
+<img src="img/user/goldarte/1.jpg" height=150> <img src="img/user/goldarte/2.jpg" height=150>
+
+**Flight video:**
+
+<a href="https://drive.google.com/file/d/1nQtFjEcGGLx-l4xkL5ko9ZpOTVU-WDjL/view?usp=sharing"><img height=200 src="img/user/goldarte/video.jpg"></a>
+
+---
+
+## School 548 course
+
+Special course on quadcopter design and engineering took place in october-november 2025 in School 548, Moscow. The course included UAV control theory, electronics, drone assembly and setup practice, using the Flix project.
+
+<img height=200 src="img/user/school548/1.jpg"> <img height=200 src="img/user/school548/2.jpg"> <img height=200 src="img/user/school548/3.jpg">
+
+STL files and other materials: see [here](https://drive.google.com/drive/folders/1wTUzj087LjKQQl3Lz5CjHCuobxoykhyp?usp=share_link).
+
+### Selected works
+
+Author: [KiraFlux](https://t.me/@kiraflux_0XC0000005).<br>
+Description: **custom ESPNOW remote control** was implemented, modified firmware to support ESPNOW protocol.<br>
+Telegram posts: [1](https://t.me/opensourcequadcopter/106), [2](https://t.me/opensourcequadcopter/114).<br>
+Modified Flix firmware: https://github.com/KiraFlux/flix/tree/klyax.<br>
+Remote control project: https://github.com/KiraFlux/ESP32-DJC.<br>
+Drone design: https://github.com/KiraFlux/Klyax.<br>
+
+<img src="img/user/school548/kiraflux1.jpg" height=150> <img src="img/user/school548/kiraflux2.jpg" height=150>
+
+**ESPNOW remote control demonstration**:
+
+<img height=200 src="img/user/school548/kiraflux-video.jpg"><a href="https://drive.google.com/file/d/1soHDAeHQWnm97Y4dg4nWevJuMiTdJJXW/view?usp=sharing"></a>
+
+Author: [tolyan4krut](https://t.me/tolyan4krut).<br>
+Description: the first drone based on ESP32-S3-CAM board **with a camera**, implementing Wi-Fi video streaming. Runs HTTP server and HTTP video stream.<br>
+Modified Flix firmware: https://github.com/CatRey/Flix-Camera-Streaming.<br>
+[Telegram post](https://t.me/opensourcequadcopter/117).
+
+<img src="img/user/school548/tolyan4krut.jpg" height=150>
+
+**Video streaming and flight demonstration**:
+
+<a href="https://drive.google.com/file/d/1KuOBsujLsk7q8FoqKD8u7uoq4ptS5onp/view?usp=sharing"><img height=200 src="img/user/school548/tolyan4krut-video.jpg"></a>
+
+Author: [Vlad Tolshinov](https://t.me/Vlad_Tolshinov).<br>
+Description: custom frame with enlarged arm length, which provides very high flight stability, 65 mm props.
+
+<img src="img/user/school548/vlad_tolshinov1.jpg" height=150> <img src="img/user/school548/vlad_tolshinov2.jpg" height=150>
+
+**Flight video**:
+
+<a href="https://drive.google.com/file/d/1zu00DZxhC7DJ9Z2mYjtxdNQqOOLAyYbp/view?usp=sharing"><img height=200 src="img/user/school548/vlad_tolshinov-video.jpg"></a>
+
+---
+
 ## RoboCamp
 
 Author: RoboCamp participants.<br>
 Description: 3D-printed and wooden frames, ESP32 Mini, DC-DC buck-boost converters. BetaFPV LiteRadio 3 to control the drones via Wi-Fi connection.<br>
 Features: altitude hold, obstacle avoidance, autonomous flight elements.<br>
-Some of the designed model files: https://drive.google.com/drive/folders/18YHWGquKeIevzrMH4-OUT-zKXMETTEUu?usp=share_link.
+Some of the designed model files: see [here](https://drive.google.com/drive/folders/18YHWGquKeIevzrMH4-OUT-zKXMETTEUu?usp=share_link).
 
 RoboCamp took place in July 2025, Saint Petersburg, where 9 participants designed and built their own drones using the Flix project, and then modified the firmware to complete specific flight tasks.
 

flix/cli.ino

@@ -6,23 +6,28 @@
 #include "pid.h"
 #include "vector.h"
 #include "util.h"
+#include "lpf.h"
 
 extern const int MOTOR_REAR_LEFT, MOTOR_REAR_RIGHT, MOTOR_FRONT_RIGHT, MOTOR_FRONT_LEFT;
-extern const int ACRO, STAB, AUTO;
+extern const int RAW, ACRO, STAB, AUTO;
+extern const int W_AP, W_STA, W_ESPNOW;
 extern float t, dt, loopRate;
 extern uint16_t channels[16];
-extern float controlRoll, controlPitch, controlThrottle, controlYaw, controlMode;
+extern float controlTime;
 extern int mode;
 extern bool armed;
+extern LowPassFilter<Vector> gyroBiasFilter;
+extern float voltage;
 
 const char* motd =
-"\nWelcome to\n"
 " _______  __       __  ___   ___\n"
 "|   ____||  |     |  | \\  \\ /  /\n"
 "|  |__   |  |     |  |  \\  V  /\n"
 "|   __|  |  |     |  |   >   <\n"
 "|  |     |  `----.|  |  /  .  \\\n"
 "|__|     |_______||__| /__/ \\__\\\n\n"
+"(C) Oleg Kalachev\n"
+"https://github.com/okalachev/flix\n\n"
 "Commands:\n\n"
 "help - show help\n"
 "p - show all parameters\n"
@@ -35,8 +40,13 @@ const char* motd =
 "imu - show IMU data\n"
 "arm - arm the drone\n"
 "disarm - disarm the drone\n"
-"stab/acro/auto - set mode\n"
+"raw/stab/acro/auto - set mode\n"
 "rc - show RC data\n"
+"pw - show power info\n"
+"wifi - show Wi-Fi info\n"
+"ap <ssid> <password> - setup Wi-Fi access point\n"
+"sta <ssid> <password> - setup Wi-Fi client mode\n"
+"espnow <mac> [<key>] - setup ESP-NOW peer\n"
 "mot - show motor output\n"
 "log [dump] - print log header [and data]\n"
 "cr - calibrate RC\n"
@@ -53,9 +63,7 @@ void print(const char* format, ...) {
 	vsnprintf(buf, sizeof(buf), format, args);
 	va_end(args);
 	Serial.print(buf);
-#if WIFI_ENABLED
 	mavlinkPrint(buf);
-#endif
 }
 
 void pause(float duration) {
@@ -63,9 +71,7 @@ void pause(float duration) {
 	while (t - start < duration) {
 		step();
 		handleInput();
-#if WIFI_ENABLED
 		processMavlink();
-#endif
 		delay(50);
 	}
 }
@@ -93,7 +99,7 @@ void doCommand(String str, bool echo = false) {
 	} else if (command == "p") {
 		bool success = setParameter(arg0.c_str(), arg1.toFloat());
 		if (success) {
-			print("%s = %g\n", arg0.c_str(), arg1.toFloat());
+			print("%s = %g\n", arg0.c_str(), getParameter(arg0.c_str()));
 		} else {
 			print("Parameter not found: %s\n", arg0.c_str());
 		}
@@ -116,6 +122,8 @@ void doCommand(String str, bool echo = false) {
 		armed = true;
 	} else if (command == "disarm") {
 		armed = false;
+	} else if (command == "raw") {
+		mode = RAW;
 	} else if (command == "stab") {
 		mode = STAB;
 	} else if (command == "acro") {
@@ -129,8 +137,19 @@ void doCommand(String str, bool echo = false) {
 		}
 		print("\nroll: %g pitch: %g yaw: %g throttle: %g mode: %g\n",
 			controlRoll, controlPitch, controlYaw, controlThrottle, controlMode);
+		print("time: %.1f\n", controlTime);
 		print("mode: %s\n", getModeName());
 		print("armed: %d\n", armed);
+	} else if (command == "pw") {
+		print("Voltage: %.1f V\n", voltage);
+	} else if (command == "wifi") {
+		printWiFiInfo();
+	} else if (command == "ap") {
+		configWiFi(W_AP, arg0.c_str(), arg1.c_str());
+	} else if (command == "sta") {
+		configWiFi(W_STA, arg0.c_str(), arg1.c_str());
+	} else if (command == "espnow") {
+		configWiFi(W_ESPNOW, arg0.c_str(), arg1.c_str());
 	} else if (command == "mot") {
 		print("front-right %g front-left %g rear-right %g rear-left %g\n",
 			motors[MOTOR_FRONT_RIGHT], motors[MOTOR_FRONT_LEFT], motors[MOTOR_REAR_RIGHT], motors[MOTOR_REAR_LEFT]);
@@ -154,6 +173,7 @@ void doCommand(String str, bool echo = false) {
 		print("Chip: %s\n", ESP.getChipModel());
 		print("Temperature: %.1f °C\n", temperatureRead());
 		print("Free heap: %d\n", ESP.getFreeHeap());
+		print("Firmware: " __DATE__ " " __TIME__ "\n");
 		// Print tasks table
 		print("Num  Task                Stack  Prio  Core  CPU%%\n");
 		int taskCount = uxTaskGetNumberOfTasks();
@@ -164,12 +184,13 @@ void doCommand(String str, bool echo = false) {
 			String core = systemState[i].xCoreID == tskNO_AFFINITY ? "*" : String(systemState[i].xCoreID);
 			int cpuPercentage = systemState[i].ulRunTimeCounter / (totalRunTime / 100);
 			print("%-5d%-20s%-7d%-6d%-6s%d\n",systemState[i].xTaskNumber, systemState[i].pcTaskName,
-				systemState[i].usStackHighWaterMark, systemState[i].uxCurrentPriority, core, cpuPercentage);
+				systemState[i].usStackHighWaterMark, systemState[i].uxCurrentPriority, core.c_str(), cpuPercentage);
 		}
 		delete[] systemState;
 #endif
 	} else if (command == "reset") {
 		attitude = Quaternion();
+		gyroBiasFilter.reset();
 	} else if (command == "reboot") {
 		ESP.restart();
 	} else {

flix/control.ino

@@ -34,10 +34,16 @@
 #define TILT_MAX radians(30)
 #define RATES_D_LPF_ALPHA 0.2 // cutoff frequency ~ 40 Hz
 
-const int MANUAL = 0, ACRO = 1, STAB = 2, AUTO = 3; // flight modes
+const int RAW = 0, ACRO = 1, STAB = 2, AUTO = 3; // flight modes
 int mode = STAB;
 bool armed = false;
 
+Quaternion attitudeTarget;
+Vector ratesTarget;
+Vector ratesExtra; // feedforward rates
+Vector torqueTarget;
+float thrustTarget;
+
 PID rollRatePID(ROLLRATE_P, ROLLRATE_I, ROLLRATE_D, ROLLRATE_I_LIM, RATES_D_LPF_ALPHA);
 PID pitchRatePID(PITCHRATE_P, PITCHRATE_I, PITCHRATE_D, PITCHRATE_I_LIM, RATES_D_LPF_ALPHA);
 PID yawRatePID(YAWRATE_P, YAWRATE_I, YAWRATE_D);
@@ -46,12 +52,7 @@ PID pitchPID(PITCH_P, PITCH_I, PITCH_D);
 PID yawPID(YAW_P, 0, 0);
 Vector maxRate(ROLLRATE_MAX, PITCHRATE_MAX, YAWRATE_MAX);
 float tiltMax = TILT_MAX;
-
+int flightModes[] = {STAB, STAB, STAB}; // map for rc mode switch
-Quaternion attitudeTarget;
-Vector ratesTarget;
-Vector ratesExtra; // feedforward rates
-Vector torqueTarget;
-float thrustTarget;
 
 extern const int MOTOR_REAR_LEFT, MOTOR_REAR_RIGHT, MOTOR_FRONT_RIGHT, MOTOR_FRONT_LEFT;
 extern float controlRoll, controlPitch, controlThrottle, controlYaw, controlMode;
@@ -65,16 +66,17 @@ void control() {
 }
 
 void interpretControls() {
-	// NOTE: put ACRO or MANUAL modes there if you want to use them
+	if (controlMode < 0.25) mode = flightModes[0];
-	if (controlMode < 0.25) mode = STAB;
+	else if (controlMode <= 0.75) mode = flightModes[1];
-	if (controlMode < 0.75) mode = STAB;
+	else if (controlMode > 0.75) mode = flightModes[2];
-	if (controlMode > 0.75) mode = STAB;
 
 	if (mode == AUTO) return; // pilot is not effective in AUTO mode
 
 	if (controlThrottle < 0.05 && controlYaw > 0.95) armed = true; // arm gesture
 	if (controlThrottle < 0.05 && controlYaw < -0.95) armed = false; // disarm gesture
 
+	if (abs(controlYaw) < 0.1) controlYaw = 0; // yaw dead zone
+
 	thrustTarget = controlThrottle;
 
 	if (mode == STAB) {
@@ -91,10 +93,10 @@ void interpretControls() {
 		ratesTarget.z = -controlYaw * maxRate.z; // positive yaw stick means clockwise rotation in FLU
 	}
 
-	if (mode == MANUAL) { // passthrough mode
+	if (mode == RAW) { // direct torque control
 		attitudeTarget.invalidate(); // skip attitude control
 		ratesTarget.invalidate(); // skip rate control
-		torqueTarget = Vector(controlRoll, controlPitch, -controlYaw) * 0.01;
+		torqueTarget = Vector(controlRoll, controlPitch, -controlYaw) * 0.1;
 	}
 }
 
@@ -147,15 +149,28 @@ void controlTorque() {
 	motors[MOTOR_REAR_LEFT] = thrustTarget + torqueTarget.x + torqueTarget.y - torqueTarget.z;
 	motors[MOTOR_REAR_RIGHT] = thrustTarget - torqueTarget.x + torqueTarget.y + torqueTarget.z;
 
+	desaturate(motors[MOTOR_FRONT_LEFT], motors[MOTOR_FRONT_RIGHT], motors[MOTOR_REAR_LEFT], motors[MOTOR_REAR_RIGHT]);
+
 	motors[0] = constrain(motors[0], 0, 1);
 	motors[1] = constrain(motors[1], 0, 1);
 	motors[2] = constrain(motors[2], 0, 1);
 	motors[3] = constrain(motors[3], 0, 1);
 }
 
+void desaturate(float& a, float& b, float& c, float& d) {
+	float maxThrust = max(max(a, b), max(c, d));
+	if (maxThrust > 1) {
+		float diff = maxThrust - 1;
+		a -= diff;
+		b -= diff;
+		c -= diff;
+		d -= diff;
+	}
+}
+
 const char* getModeName() {
 	switch (mode) {
-		case MANUAL: return "MANUAL";
+		case RAW: return "RAW";
 		case ACRO: return "ACRO";
 		case STAB: return "STAB";
 		case AUTO: return "AUTO";

flix/estimate.ino

@@ -1,24 +1,29 @@
 // Copyright (c) 2023 Oleg Kalachev <okalachev@gmail.com>
 // Repository: https://github.com/okalachev/flix
 
-// Attitude estimation from gyro and accelerometer
+// Attitude estimation using gyro and accelerometer
 
 #include "quaternion.h"
 #include "vector.h"
 #include "lpf.h"
 #include "util.h"
 
-#define WEIGHT_ACC 0.003
+Vector rates; // estimated angular rates, rad/s
-#define RATES_LFP_ALPHA 0.2 // cutoff frequency ~ 40 Hz
+Quaternion attitude; // estimated attitude
+bool landed;
+
+float accWeight = 0.003;
+float levelWeight = 0.0002;
+LowPassFilter<Vector> ratesFilter(0.2); // cutoff frequency ~ 40 Hz
 
 void estimate() {
 	applyGyro();
 	applyAcc();
+	applyLevel();
 }
 
 void applyGyro() {
 	// filter gyro to get angular rates
-	static LowPassFilter<Vector> ratesFilter(RATES_LFP_ALPHA);
 	rates = ratesFilter.update(gyro);
 
 	// apply rates to attitude
@@ -34,8 +39,17 @@ void applyAcc() {
 
 	// calculate accelerometer correction
 	Vector up = Quaternion::rotateVector(Vector(0, 0, 1), attitude);
-	Vector correction = Vector::rotationVectorBetween(acc, up) * WEIGHT_ACC;
+	Vector correction = Vector::rotationVectorBetween(acc, up) * accWeight;
 
 	// apply correction
 	attitude = Quaternion::rotate(attitude, Quaternion::fromRotationVector(correction));
 }
+
+void applyLevel() {
+	if (landed) return;
+
+	// assume the pilot keeps the drone more or less level in flight
+	Vector up = Quaternion::rotateVector(Vector(0, 0, 1), attitude);
+	Vector correction = Vector::rotationVectorBetween(Vector(0, 0, 1), up) * levelWeight;
+	attitude = Quaternion::rotate(attitude, Quaternion::fromRotationVector(correction));
+}

flix/flix.ino

@@ -7,30 +7,23 @@
 #include "quaternion.h"
 #include "util.h"
 
-#define WIFI_ENABLED 1
+extern float t, dt;
-
+extern float controlRoll, controlPitch, controlYaw, controlThrottle, controlMode;
-float t = NAN; // current step time, s
+extern Vector gyro, acc;
-float dt; // time delta from previous step, s
+extern Vector rates;
-float controlRoll, controlPitch, controlYaw, controlThrottle; // pilot's inputs, range [-1, 1]
+extern Quaternion attitude;
-float controlMode = NAN;
+extern bool landed;
-Vector gyro; // gyroscope data
+extern float motors[4];
-Vector acc; // accelerometer data, m/s/s
-Vector rates; // filtered angular rates, rad/s
-Quaternion attitude; // estimated attitude
-bool landed; // are we landed and stationary
-float motors[4]; // normalized motors thrust in range [0..1]
 
 void setup() {
 	Serial.begin(115200);
 	print("Initializing flix\n");
-	disableBrownOut();
 	setupParameters();
+	setupPower();
 	setupLED();
-	setupMotors();
 	setLED(true);
-#if WIFI_ENABLED
+	setupMotors();
 	setupWiFi();
-#endif
 	setupIMU();
 	setupRC();
 	setLED(false);
@@ -45,9 +38,8 @@ void loop() {
 	control();
 	sendMotors();
 	handleInput();
-#if WIFI_ENABLED
 	processMavlink();
-#endif
+	readVoltage();
 	logData();
 	syncParameters();
 }

flix/imu.ino

@@ -10,10 +10,16 @@
 #include "util.h"
 
 MPU9250 imu(SPI);
+Vector imuRotation(0, 0, PI / 2); // imu orientation as Euler angles
 
+Vector gyro; // gyroscope output, rad/s
+Vector gyroBias;
+
+Vector acc; // accelerometer output, m/s/s
 Vector accBias;
 Vector accScale(1, 1, 1);
-Vector gyroBias;
+
+LowPassFilter<Vector> gyroBiasFilter(0.001);
 
 void setupIMU() {
 	print("Setup IMU\n");
@@ -37,24 +43,16 @@ void readIMU() {
 	// apply scale and bias
 	acc = (acc - accBias) / accScale;
 	gyro = gyro - gyroBias;
-	// rotate
+	// rotate to body frame
-	rotateIMU(acc);
+	Quaternion rotation = Quaternion::fromEuler(imuRotation);
-	rotateIMU(gyro);
+	acc = Quaternion::rotateVector(acc, rotation.inversed());
-}
+	gyro = Quaternion::rotateVector(gyro, rotation.inversed());
-
-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 calibrateGyroOnce() {
 	static Delay landedDelay(2);
 	if (!landedDelay.update(landed)) return; // calibrate only if definitely stationary
-
+	gyroBias = gyroBiasFilter.update(gyro);
-	static LowPassFilter<Vector> gyroCalibrationFilter(0.001);
-	gyroBias = gyroCalibrationFilter.update(gyro);
 }
 
 void calibrateAccel() {
@@ -123,7 +121,7 @@ void printIMUInfo() {
 	print("model: %s\n", imu.getModel());
 	print("who am I: 0x%02X\n", imu.whoAmI());
 	print("rate: %.0f\n", loopRate);
-	print("gyro: %f %f %f\n", rates.x, rates.y, rates.z);
+	print("gyro: %f %f %f\n", gyro.x, gyro.y, gyro.z);
 	print("acc: %f %f %f\n", acc.x, acc.y, acc.z);
 	imu.waitForData();
 	Vector rawGyro, rawAcc;

flix/lpf.h

@@ -14,15 +14,10 @@ public:
 	LowPassFilter(float alpha): alpha(alpha) {};
 
 	T update(const T input) {
-		if (alpha == 1) { // filter disabled
+		if (!init) {
-			return input;
+			init = true;
+			return output = input;
 		}
-
-		if (!initialized) {
-			output = input;
-			initialized = true;
-		}
-
 		return output += alpha * (input - output);
 	}
 
@@ -31,9 +26,9 @@ public:
 	}
 
 	void reset() {
-		initialized = false;
+		init = false;
 	}
 
 private:
-	bool initialized = false;
+	bool init = false;
 };

flix/mavlink.ino

@@ -3,22 +3,19 @@
 
 // MAVLink communication
 
-#if WIFI_ENABLED
-
 #include <MAVLink.h>
 #include "util.h"
 
-#define SYSTEM_ID 1
+extern float controlTime;
-#define MAVLINK_RATE_SLOW 1
+extern float voltage;
-#define MAVLINK_RATE_FAST 10
+
-#define MAVLINK_CONTROL_YAW_DEAD_ZONE 0.1f
+int mavlinkSysId = 1;
+Rate telemetryFast(10);
+Rate telemetrySlow(2);
 
 bool mavlinkConnected = false;
 String mavlinkPrintBuffer;
 
-extern float controlTime;
-extern float controlRoll, controlPitch, controlThrottle, controlYaw, controlMode;
-
 void processMavlink() {
 	sendMavlink();
 	receiveMavlink();
@@ -30,10 +27,8 @@ void sendMavlink() {
 	mavlink_message_t msg;
 	uint32_t time = t * 1000;
 
-	static Rate slow(MAVLINK_RATE_SLOW), fast(MAVLINK_RATE_FAST);
+	if (telemetrySlow) {
-
+		mavlink_msg_heartbeat_pack(mavlinkSysId, MAV_COMP_ID_AUTOPILOT1, &msg, MAV_TYPE_QUADROTOR, MAV_AUTOPILOT_GENERIC,
-	if (slow) {
-		mavlink_msg_heartbeat_pack(SYSTEM_ID, MAV_COMP_ID_AUTOPILOT1, &msg, MAV_TYPE_QUADROTOR, MAV_AUTOPILOT_GENERIC,
 			(armed ? MAV_MODE_FLAG_SAFETY_ARMED : 0) |
 			((mode == STAB) ? MAV_MODE_FLAG_STABILIZE_ENABLED : 0) |
 			((mode == AUTO) ? MAV_MODE_FLAG_AUTO_ENABLED : MAV_MODE_FLAG_MANUAL_INPUT_ENABLED),
@@ -42,28 +37,35 @@ void sendMavlink() {
 
 		if (!mavlinkConnected) return; // send only heartbeat until connected
 
-		mavlink_msg_extended_sys_state_pack(SYSTEM_ID, MAV_COMP_ID_AUTOPILOT1, &msg,
+		mavlink_msg_extended_sys_state_pack(mavlinkSysId, MAV_COMP_ID_AUTOPILOT1, &msg,
 			MAV_VTOL_STATE_UNDEFINED, landed ? MAV_LANDED_STATE_ON_GROUND : MAV_LANDED_STATE_IN_AIR);
 		sendMessage(&msg);
+
+		uint16_t voltages[] = {voltage * 1000, UINT16_MAX, UINT16_MAX, UINT16_MAX, UINT16_MAX, UINT16_MAX, UINT16_MAX, UINT16_MAX, UINT16_MAX, UINT16_MAX};
+		uint16_t voltagesExt[] = {0, 0, 0, 0};
+		float remaining = constrain(mapf(voltage, 3.4, 4.2, 0, 1), 0, 1);
+		mavlink_msg_battery_status_pack(mavlinkSysId, MAV_COMP_ID_AUTOPILOT1, &msg, 0, MAV_BATTERY_FUNCTION_ALL,
+			MAV_BATTERY_TYPE_LIPO, INT16_MAX, voltages, -1, -1, -1, remaining * 100, 0, MAV_BATTERY_CHARGE_STATE_OK, voltagesExt, 0, 0);
+		if (valid(voltage)) sendMessage(&msg);
 	}
 
-	if (fast && mavlinkConnected) {
+	if (telemetryFast && mavlinkConnected) {
-		const float zeroQuat[] = {0, 0, 0, 0};
+		const float offset[] = {0, 0, 0, 0};
-		mavlink_msg_attitude_quaternion_pack(SYSTEM_ID, MAV_COMP_ID_AUTOPILOT1, &msg,
+		mavlink_msg_attitude_quaternion_pack(mavlinkSysId, MAV_COMP_ID_AUTOPILOT1, &msg,
-			time, attitude.w, attitude.x, -attitude.y, -attitude.z, rates.x, -rates.y, -rates.z, zeroQuat); // convert to frd
+			time, attitude.w, attitude.x, -attitude.y, -attitude.z, rates.x, -rates.y, -rates.z, offset); // convert to frd
 		sendMessage(&msg);
 
-		mavlink_msg_rc_channels_raw_pack(SYSTEM_ID, MAV_COMP_ID_AUTOPILOT1, &msg, controlTime * 1000, 0,
+		mavlink_msg_rc_channels_raw_pack(mavlinkSysId, MAV_COMP_ID_AUTOPILOT1, &msg, controlTime * 1000, 0,
 			channels[0], channels[1], channels[2], channels[3], channels[4], channels[5], channels[6], channels[7], UINT8_MAX);
 		if (channels[0] != 0) sendMessage(&msg); // 0 means no RC input
 
 		float controls[8];
 		memcpy(controls, motors, sizeof(motors));
-		mavlink_msg_actuator_control_target_pack(SYSTEM_ID, MAV_COMP_ID_AUTOPILOT1, &msg, time, 0, controls);
+		mavlink_msg_actuator_control_target_pack(mavlinkSysId, MAV_COMP_ID_AUTOPILOT1, &msg, time, 0, controls);
 		sendMessage(&msg);
 
-		mavlink_msg_scaled_imu_pack(SYSTEM_ID, MAV_COMP_ID_AUTOPILOT1, &msg, time,
+		mavlink_msg_scaled_imu_pack(mavlinkSysId, MAV_COMP_ID_AUTOPILOT1, &msg, time,
-			acc.x * 1000, -acc.y * 1000, -acc.z * 1000, // convert to frd
+			acc.x / ONE_G * 1000, -acc.y / ONE_G * 1000, -acc.z / ONE_G * 1000, // convert to frd
 			gyro.x * 1000, -gyro.y * 1000, -gyro.z * 1000,
 			0, 0, 0, 0);
 		sendMessage(&msg);
@@ -97,7 +99,7 @@ void handleMavlink(const void *_msg) {
 	if (msg.msgid == MAVLINK_MSG_ID_MANUAL_CONTROL) {
 		mavlink_manual_control_t m;
 		mavlink_msg_manual_control_decode(&msg, &m);
-		if (m.target && m.target != SYSTEM_ID) return; // 0 is broadcast
+		if (m.target && m.target != mavlinkSysId) return; // 0 is broadcast
 
 		controlThrottle = m.z / 1000.0f;
 		controlPitch = m.x / 1000.0f;
@@ -105,18 +107,16 @@ void handleMavlink(const void *_msg) {
 		controlYaw = m.r / 1000.0f;
 		controlMode = NAN;
 		controlTime = t;
-
-		if (abs(controlYaw) < MAVLINK_CONTROL_YAW_DEAD_ZONE) controlYaw = 0;
 	}
 
 	if (msg.msgid == MAVLINK_MSG_ID_PARAM_REQUEST_LIST) {
 		mavlink_param_request_list_t m;
 		mavlink_msg_param_request_list_decode(&msg, &m);
-		if (m.target_system && m.target_system != SYSTEM_ID) return;
+		if (m.target_system && m.target_system != mavlinkSysId) return;
 
 		mavlink_message_t msg;
 		for (int i = 0; i < parametersCount(); i++) {
-			mavlink_msg_param_value_pack(SYSTEM_ID, MAV_COMP_ID_AUTOPILOT1, &msg,
+			mavlink_msg_param_value_pack(mavlinkSysId, MAV_COMP_ID_AUTOPILOT1, &msg,
 				getParameterName(i), getParameter(i), MAV_PARAM_TYPE_REAL32, parametersCount(), i);
 			sendMessage(&msg);
 		}
@@ -125,7 +125,7 @@ void handleMavlink(const void *_msg) {
 	if (msg.msgid == MAVLINK_MSG_ID_PARAM_REQUEST_READ) {
 		mavlink_param_request_read_t m;
 		mavlink_msg_param_request_read_decode(&msg, &m);
-		if (m.target_system && m.target_system != SYSTEM_ID) return;
+		if (m.target_system && m.target_system != mavlinkSysId) return;
 
 		char name[MAVLINK_MSG_PARAM_REQUEST_READ_FIELD_PARAM_ID_LEN + 1];
 		strlcpy(name, m.param_id, sizeof(name)); // param_id might be not null-terminated
@@ -134,7 +134,7 @@ void handleMavlink(const void *_msg) {
 			memcpy(name, getParameterName(m.param_index), 16);
 		}
 		mavlink_message_t msg;
-		mavlink_msg_param_value_pack(SYSTEM_ID, MAV_COMP_ID_AUTOPILOT1, &msg,
+		mavlink_msg_param_value_pack(mavlinkSysId, MAV_COMP_ID_AUTOPILOT1, &msg,
 			name, value, MAV_PARAM_TYPE_REAL32, parametersCount(), m.param_index);
 		sendMessage(&msg);
 	}
@@ -142,32 +142,33 @@ void handleMavlink(const void *_msg) {
 	if (msg.msgid == MAVLINK_MSG_ID_PARAM_SET) {
 		mavlink_param_set_t m;
 		mavlink_msg_param_set_decode(&msg, &m);
-		if (m.target_system && m.target_system != SYSTEM_ID) return;
+		if (m.target_system && m.target_system != mavlinkSysId) return;
 
 		char name[MAVLINK_MSG_PARAM_SET_FIELD_PARAM_ID_LEN + 1];
 		strlcpy(name, m.param_id, sizeof(name)); // param_id might be not null-terminated
-		setParameter(name, m.param_value);
+		bool success = setParameter(name, m.param_value);
+		if (!success) return;
 		// send ack
 		mavlink_message_t msg;
-		mavlink_msg_param_value_pack(SYSTEM_ID, MAV_COMP_ID_AUTOPILOT1, &msg,
+		mavlink_msg_param_value_pack(mavlinkSysId, MAV_COMP_ID_AUTOPILOT1, &msg,
-			m.param_id, m.param_value, MAV_PARAM_TYPE_REAL32, parametersCount(), 0); // index is unknown
+			m.param_id, getParameter(name), MAV_PARAM_TYPE_REAL32, parametersCount(), 0); // index is unknown
 		sendMessage(&msg);
 	}
 
 	if (msg.msgid == MAVLINK_MSG_ID_MISSION_REQUEST_LIST) { // handle to make qgc happy
 		mavlink_mission_request_list_t m;
 		mavlink_msg_mission_request_list_decode(&msg, &m);
-		if (m.target_system && m.target_system != SYSTEM_ID) return;
+		if (m.target_system && m.target_system != mavlinkSysId) return;
 
 		mavlink_message_t msg;
-		mavlink_msg_mission_count_pack(SYSTEM_ID, MAV_COMP_ID_AUTOPILOT1, &msg, 0, 0, 0, MAV_MISSION_TYPE_MISSION, 0);
+		mavlink_msg_mission_count_pack(mavlinkSysId, MAV_COMP_ID_AUTOPILOT1, &msg, 0, 0, 0, MAV_MISSION_TYPE_MISSION, 0);
 		sendMessage(&msg);
 	}
 
 	if (msg.msgid == MAVLINK_MSG_ID_SERIAL_CONTROL) {
 		mavlink_serial_control_t m;
 		mavlink_msg_serial_control_decode(&msg, &m);
-		if (m.target_system && m.target_system != SYSTEM_ID) return;
+		if (m.target_system && m.target_system != mavlinkSysId) return;
 
 		char data[MAVLINK_MSG_SERIAL_CONTROL_FIELD_DATA_LEN + 1];
 		strlcpy(data, (const char *)m.data, m.count); // data might be not null-terminated
@@ -179,7 +180,7 @@ void handleMavlink(const void *_msg) {
 
 		mavlink_set_attitude_target_t m;
 		mavlink_msg_set_attitude_target_decode(&msg, &m);
-		if (m.target_system && m.target_system != SYSTEM_ID) return;
+		if (m.target_system && m.target_system != mavlinkSysId) return;
 
 		// copy attitude, rates and thrust targets
 		ratesTarget.x = m.body_roll_rate;
@@ -201,7 +202,7 @@ void handleMavlink(const void *_msg) {
 
 		mavlink_set_actuator_control_target_t m;
 		mavlink_msg_set_actuator_control_target_decode(&msg, &m);
-		if (m.target_system && m.target_system != SYSTEM_ID) return;
+		if (m.target_system && m.target_system != mavlinkSysId) return;
 
 		attitudeTarget.invalidate();
 		ratesTarget.invalidate();
@@ -213,12 +214,12 @@ void handleMavlink(const void *_msg) {
 	if (msg.msgid == MAVLINK_MSG_ID_LOG_REQUEST_DATA) {
 		mavlink_log_request_data_t m;
 		mavlink_msg_log_request_data_decode(&msg, &m);
-		if (m.target_system && m.target_system != SYSTEM_ID) return;
+		if (m.target_system && m.target_system != mavlinkSysId) return;
 
 		// Send all log records
 		for (int i = 0; i < sizeof(logBuffer) / sizeof(logBuffer[0]); i++) {
 			mavlink_message_t msg;
-			mavlink_msg_log_data_pack(SYSTEM_ID, MAV_COMP_ID_AUTOPILOT1, &msg, 0, i,
+			mavlink_msg_log_data_pack(mavlinkSysId, MAV_COMP_ID_AUTOPILOT1, &msg, 0, i,
 				sizeof(logBuffer[0]), (uint8_t *)logBuffer[i]);
 			sendMessage(&msg);
 		}
@@ -228,13 +229,13 @@ void handleMavlink(const void *_msg) {
 	if (msg.msgid == MAVLINK_MSG_ID_COMMAND_LONG) {
 		mavlink_command_long_t m;
 		mavlink_msg_command_long_decode(&msg, &m);
-		if (m.target_system && m.target_system != SYSTEM_ID) return;
+		if (m.target_system && m.target_system != mavlinkSysId) return;
 		mavlink_message_t response;
 		bool accepted = false;
 
 		if (m.command == MAV_CMD_REQUEST_MESSAGE && m.param1 == MAVLINK_MSG_ID_AUTOPILOT_VERSION) {
 			accepted = true;
-			mavlink_msg_autopilot_version_pack(SYSTEM_ID, MAV_COMP_ID_AUTOPILOT1, &response,
+			mavlink_msg_autopilot_version_pack(mavlinkSysId, MAV_COMP_ID_AUTOPILOT1, &response,
 				MAV_PROTOCOL_CAPABILITY_PARAM_FLOAT | MAV_PROTOCOL_CAPABILITY_MAVLINK2, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0);
 			sendMessage(&response);
 		}
@@ -253,7 +254,7 @@ void handleMavlink(const void *_msg) {
 
 		// send command ack
 		mavlink_message_t ack;
-		mavlink_msg_command_ack_pack(SYSTEM_ID, MAV_COMP_ID_AUTOPILOT1, &ack, m.command, accepted ? MAV_RESULT_ACCEPTED : MAV_RESULT_UNSUPPORTED, UINT8_MAX, 0, msg.sysid, msg.compid);
+		mavlink_msg_command_ack_pack(mavlinkSysId, MAV_COMP_ID_AUTOPILOT1, &ack, m.command, accepted ? MAV_RESULT_ACCEPTED : MAV_RESULT_UNSUPPORTED, UINT8_MAX, 0, msg.sysid, msg.compid);
 		sendMessage(&ack);
 	}
 }
@@ -270,7 +271,7 @@ void sendMavlinkPrint() {
 		char data[MAVLINK_MSG_SERIAL_CONTROL_FIELD_DATA_LEN + 1];
 		strlcpy(data, str + i, sizeof(data));
 		mavlink_message_t msg;
-		mavlink_msg_serial_control_pack(SYSTEM_ID, MAV_COMP_ID_AUTOPILOT1, &msg,
+		mavlink_msg_serial_control_pack(mavlinkSysId, MAV_COMP_ID_AUTOPILOT1, &msg,
 			SERIAL_CONTROL_DEV_SHELL,
 			i + MAVLINK_MSG_SERIAL_CONTROL_FIELD_DATA_LEN < strlen(str) ? SERIAL_CONTROL_FLAG_MULTI : 0, // more chunks to go
 			0, 0, strlen(data), (uint8_t *)data, 0, 0);
@@ -278,5 +279,3 @@ void sendMavlinkPrint() {
 	}
 	mavlinkPrintBuffer.clear();
 }
-
-#endif

flix/motors.ino

@@ -1,23 +1,19 @@
 // Copyright (c) 2023 Oleg Kalachev <okalachev@gmail.com>
 // Repository: https://github.com/okalachev/flix
 
-// Motors output control using MOSFETs
+// PWM control for motors
-// In case of using ESCs, change PWM_STOP, PWM_MIN and PWM_MAX to appropriate values in μs, decrease PWM_FREQUENCY (to 400)
 
 #include "util.h"
 
-#define MOTOR_0_PIN 12 // rear left
+float motors[4]; // normalized motor thrusts in range [0..1]
-#define MOTOR_1_PIN 13 // rear right
-#define MOTOR_2_PIN 14 // front right
-#define MOTOR_3_PIN 15 // front left
 
-#define PWM_FREQUENCY 78000
+int motorPins[4] = {12, 13, 14, 15}; // default pin numbers
-#define PWM_RESOLUTION 10
+int pwmFrequency = 78000;
-#define PWM_STOP 0
+int pwmResolution = 10;
-#define PWM_MIN 0
+int pwmStop = 0;
-#define PWM_MAX 1000000 / PWM_FREQUENCY
+int pwmMin = 0;
+int pwmMax = -1; // -1 means duty cycle mode
 
-// Motors array indexes:
 const int MOTOR_REAR_LEFT = 0;
 const int MOTOR_REAR_RIGHT = 1;
 const int MOTOR_FRONT_RIGHT = 2;
@@ -25,30 +21,31 @@ const int MOTOR_FRONT_LEFT = 3;
 
 void setupMotors() {
 	print("Setup Motors\n");
-
 	// configure pins
-	ledcAttach(MOTOR_0_PIN, PWM_FREQUENCY, PWM_RESOLUTION);
+	for (int i = 0; i < 4; i++) {
-	ledcAttach(MOTOR_1_PIN, PWM_FREQUENCY, PWM_RESOLUTION);
+		ledcAttach(motorPins[i], pwmFrequency, pwmResolution);
-	ledcAttach(MOTOR_2_PIN, PWM_FREQUENCY, PWM_RESOLUTION);
+		pwmFrequency = ledcChangeFrequency(motorPins[i], pwmFrequency, pwmResolution); // when reconfiguring
-	ledcAttach(MOTOR_3_PIN, PWM_FREQUENCY, PWM_RESOLUTION);
+	}
-
 	sendMotors();
 	print("Motors initialized\n");
 }
 
-int getDutyCycle(float value) {
+void sendMotors() {
-	value = constrain(value, 0, 1);
+	for (int i = 0; i < 4; i++) {
-	float pwm = mapf(value, 0, 1, PWM_MIN, PWM_MAX);
+		ledcWrite(motorPins[i], getDutyCycle(motors[i]));
-	if (value == 0) pwm = PWM_STOP;
+	}
-	float duty = mapf(pwm, 0, 1000000 / PWM_FREQUENCY, 0, (1 << PWM_RESOLUTION) - 1);
-	return round(duty);
 }
 
-void sendMotors() {
+int getDutyCycle(float value) {
-	ledcWrite(MOTOR_0_PIN, getDutyCycle(motors[0]));
+	value = constrain(value, 0, 1);
-	ledcWrite(MOTOR_1_PIN, getDutyCycle(motors[1]));
+	if (pwmMax >= 0) { // pwm mode
-	ledcWrite(MOTOR_2_PIN, getDutyCycle(motors[2]));
+		float pwm = mapf(value, 0, 1, pwmMin, pwmMax);
-	ledcWrite(MOTOR_3_PIN, getDutyCycle(motors[3]));
+		if (value == 0) pwm = pwmStop;
+		float duty = mapf(pwm, 0, 1000000 / pwmFrequency, 0, (1 << pwmResolution) - 1);
+		return round(duty);
+	} else { // duty cycle mode
+		return round(value * ((1 << pwmResolution) - 1));
+	}
 }
 
 bool motorsActive() {
@@ -57,7 +54,7 @@ bool motorsActive() {
 
 void testMotor(int n) {
 	print("Testing motor %d\n", n);
-	motors[n] = 1;
+	motors[n] = 0.2;
 	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();
 	pause(3);

flix/parameters.ino

@@ -6,16 +6,28 @@
 #include <Preferences.h>
 #include "util.h"
 
-extern float channelZero[16];
+extern int channelZero[16];
-extern float channelMax[16];
+extern int channelMax[16];
-extern float rollChannel, pitchChannel, throttleChannel, yawChannel, armedChannel, modeChannel;
+extern int rollChannel, pitchChannel, throttleChannel, yawChannel, armedChannel, modeChannel;
+extern int rcRxPin;
+extern int wifiMode, wifiLongRange, udpLocalPort, udpRemotePort, espnowChannel;
+extern float rcLossTimeout, descendTime;
+extern int voltagePin;
+extern float voltageScale;
+extern LowPassFilter<float> voltageFilter;
 
 Preferences storage;
 
 struct Parameter {
-	const char *name; // max length is 15 (Preferences key limit)
+	const char *name; // max length is 15
-	float *variable;
+	bool integer;
-	float value; // cache
+	union { float *f; int *i; }; // pointer to the variable
+	float cache; // what's stored in flash
+	void (*callback)(); // called after parameter change
+	Parameter(const char *name, float *variable, void (*callback)() = nullptr) : name(name), integer(false), f(variable), callback(callback) {};
+	Parameter(const char *name, int *variable, void (*callback)() = nullptr) : name(name), integer(true), i(variable), callback(callback) {};
+	float getValue() const { return integer ? *i : *f; };
+	void setValue(const float value) { if (integer) *i = value; else *f = value; };
 };
 
 Parameter parameters[] = {
@@ -24,13 +36,16 @@ Parameter parameters[] = {
 	{"CTL_R_RATE_I", &rollRatePID.i},
 	{"CTL_R_RATE_D", &rollRatePID.d},
 	{"CTL_R_RATE_WU", &rollRatePID.windup},
+	{"CTL_R_RATE_D_A", &rollRatePID.lpf.alpha},
 	{"CTL_P_RATE_P", &pitchRatePID.p},
 	{"CTL_P_RATE_I", &pitchRatePID.i},
 	{"CTL_P_RATE_D", &pitchRatePID.d},
 	{"CTL_P_RATE_WU", &pitchRatePID.windup},
+	{"CTL_P_RATE_D_A", &pitchRatePID.lpf.alpha},
 	{"CTL_Y_RATE_P", &yawRatePID.p},
 	{"CTL_Y_RATE_I", &yawRatePID.i},
 	{"CTL_Y_RATE_D", &yawRatePID.d},
+	{"CTL_Y_RATE_D_A", &yawRatePID.lpf.alpha},
 	{"CTL_R_P", &rollPID.p},
 	{"CTL_R_I", &rollPID.i},
 	{"CTL_R_D", &rollPID.d},
@@ -42,14 +57,36 @@ Parameter parameters[] = {
 	{"CTL_R_RATE_MAX", &maxRate.x},
 	{"CTL_Y_RATE_MAX", &maxRate.z},
 	{"CTL_TILT_MAX", &tiltMax},
+	{"CTL_FLT_MODE_0", &flightModes[0]},
+	{"CTL_FLT_MODE_1", &flightModes[1]},
+	{"CTL_FLT_MODE_2", &flightModes[2]},
 	// imu
+	{"IMU_ROT_ROLL", &imuRotation.x},
+	{"IMU_ROT_PITCH", &imuRotation.y},
+	{"IMU_ROT_YAW", &imuRotation.z},
 	{"IMU_ACC_BIAS_X", &accBias.x},
 	{"IMU_ACC_BIAS_Y", &accBias.y},
 	{"IMU_ACC_BIAS_Z", &accBias.z},
 	{"IMU_ACC_SCALE_X", &accScale.x},
 	{"IMU_ACC_SCALE_Y", &accScale.y},
 	{"IMU_ACC_SCALE_Z", &accScale.z},
+	{"IMU_GYRO_BIAS_A", &gyroBiasFilter.alpha},
+	// estimate
+	{"EST_ACC_WEIGHT", &accWeight},
+	{"EST_LVL_WEIGHT", &levelWeight},
+	{"EST_RATES_LPF_A", &ratesFilter.alpha},
+	// motors
+	{"MOT_PIN_FL", &motorPins[MOTOR_FRONT_LEFT], setupMotors},
+	{"MOT_PIN_FR", &motorPins[MOTOR_FRONT_RIGHT], setupMotors},
+	{"MOT_PIN_RL", &motorPins[MOTOR_REAR_LEFT], setupMotors},
+	{"MOT_PIN_RR", &motorPins[MOTOR_REAR_RIGHT], setupMotors},
+	{"MOT_PWM_FREQ", &pwmFrequency, setupMotors},
+	{"MOT_PWM_RES", &pwmResolution, setupMotors},
+	{"MOT_PWM_STOP", &pwmStop},
+	{"MOT_PWM_MIN", &pwmMin},
+	{"MOT_PWM_MAX", &pwmMax},
 	// rc
+	{"RC_RX_PIN", &rcRxPin, setupRC},
 	{"RC_ZERO_0", &channelZero[0]},
 	{"RC_ZERO_1", &channelZero[1]},
 	{"RC_ZERO_2", &channelZero[2]},
@@ -71,17 +108,36 @@ Parameter parameters[] = {
 	{"RC_THROTTLE", &throttleChannel},
 	{"RC_YAW", &yawChannel},
 	{"RC_MODE", &modeChannel},
+	// wifi
+	{"WIFI_MODE", &wifiMode},
+	{"WIFI_PORT_LOC", &udpLocalPort},
+	{"WIFI_PORT_REM", &udpRemotePort},
+	{"WIFI_LONG_RANGE", &wifiLongRange},
+	// espnow
+	{"ESPNOW_CHANNEL", &espnowChannel},
+	// mavlink
+	{"MAV_SYS_ID", &mavlinkSysId},
+	{"MAV_RATE_SLOW", &telemetrySlow.rate},
+	{"MAV_RATE_FAST", &telemetryFast.rate},
+	// power
+	{"PWR_VOLT_PIN", &voltagePin, setupPower},
+	{"PWR_VOLT_SCALE", &voltageScale},
+	{"PWR_VOLT_LPF_A", &voltageFilter.alpha},
+	// safety
+	{"SF_RC_LOSS_TIME", &rcLossTimeout},
+	{"SF_DESCEND_TIME", &descendTime},
 };
 
 void setupParameters() {
-	storage.begin("flix", false);
+	print("Setup parameters\n");
+	storage.begin("flix");
 	// Read parameters from storage
 	for (auto &parameter : parameters) {
 		if (!storage.isKey(parameter.name)) {
-			storage.putFloat(parameter.name, *parameter.variable);
+			storage.putFloat(parameter.name, parameter.getValue()); // store default value
 		}
-		*parameter.variable = storage.getFloat(parameter.name, *parameter.variable);
+		parameter.setValue(storage.getFloat(parameter.name, 0));
-		parameter.value = *parameter.variable;
+		parameter.cache = parameter.getValue();
 	}
 }
 
@@ -96,13 +152,13 @@ const char *getParameterName(int index) {
 
 float getParameter(int index) {
 	if (index < 0 || index >= parametersCount()) return NAN;
-	return *parameters[index].variable;
+	return parameters[index].getValue();
 }
 
 float getParameter(const char *name) {
 	for (auto &parameter : parameters) {
-		if (strcmp(parameter.name, name) == 0) {
+		if (strcasecmp(parameter.name, name) == 0) {
-			return *parameter.variable;
+			return parameter.getValue();
 		}
 	}
 	return NAN;
@@ -110,8 +166,10 @@ float getParameter(const char *name) {
 
 bool setParameter(const char *name, const float value) {
 	for (auto &parameter : parameters) {
-		if (strcmp(parameter.name, name) == 0) {
+		if (strcasecmp(parameter.name, name) == 0) {
-			*parameter.variable = value;
+			if (parameter.integer && !isfinite(value)) return false; // can't set integer to NaN or Inf
+			parameter.setValue(value);
+			if (parameter.callback) parameter.callback();
 			return true;
 		}
 	}
@@ -124,16 +182,17 @@ void syncParameters() {
 	if (motorsActive()) return; // don't use flash while flying, it may cause a delay
 
 	for (auto &parameter : parameters) {
-		if (parameter.value == *parameter.variable) continue;
+		if (parameter.getValue() == parameter.cache) continue; // no change
-		if (isnan(parameter.value) && isnan(*parameter.variable)) continue; // handle NAN != NAN
+		if (isnan(parameter.getValue()) && isnan(parameter.cache)) continue; // both are NAN
-		storage.putFloat(parameter.name, *parameter.variable);
+
-		parameter.value = *parameter.variable;
+		storage.putFloat(parameter.name, parameter.getValue());
+		parameter.cache = parameter.getValue(); // update cache
 	}
 }
 
 void printParameters() {
 	for (auto &parameter : parameters) {
-		print("%s = %g\n", parameter.name, *parameter.variable);
+		print("%s = %g\n", parameter.name, parameter.getValue());
 	}
 }
 

flix/power.ino

@@ -0,0 +1,28 @@
+// Copyright (c) 2026 Oleg Kalachev <okalachev@gmail.com>
+// Repository: https://github.com/okalachev/flix
+
+// Power management
+
+#include <soc/soc.h>
+#include <soc/rtc_cntl_reg.h>
+#include "lpf.h"
+#include "util.h"
+
+float voltage = NAN;
+LowPassFilter<float> voltageFilter(0.2);
+int voltagePin = -1;
+float voltageScale = 2;
+
+void setupPower() {
+	REG_CLR_BIT(RTC_CNTL_BROWN_OUT_REG, RTC_CNTL_BROWN_OUT_ENA); // disable reset on low voltage
+	if (digitalPinToAnalogChannel(voltagePin) == -1) voltagePin = -1; // test ADC pin
+}
+
+void readVoltage() {
+	if (voltagePin < 0) return;
+	static Rate rate(10);
+	if (!rate) return;
+
+	float v = analogReadMilliVolts(voltagePin) * voltageScale / 1000.0f;
+	voltage = voltageFilter.update(v);
+}

flix/rc.ino

@@ -6,22 +6,27 @@
 #include <SBUS.h>
 #include "util.h"
 
-SBUS rc(Serial2); // NOTE: Use RC(Serial2, 16, 17) if you use the old UART2 pins
+SBUS rc(Serial1);
+int rcRxPin = -1; // -1 means disabled
 
 uint16_t channels[16]; // raw rc channels
-float controlTime; // time of the last controls update
+int channelZero[16]; // calibration zero values
-float channelZero[16]; // calibration zero values
+int channelMax[16]; // calibration max values
-float channelMax[16]; // calibration max values
 
-// Channels mapping (using float to store in parameters):
+float controlRoll, controlPitch, controlYaw, controlThrottle; // pilot's inputs, range [-1, 1]
-float rollChannel = NAN, pitchChannel = NAN, throttleChannel = NAN, yawChannel = NAN, modeChannel = NAN;
+float controlMode = NAN;
+float controlTime = NAN; // time of the last controls update
+
+int rollChannel = -1, pitchChannel = -1, throttleChannel = -1, yawChannel = -1, modeChannel = -1; // channel mapping
 
 void setupRC() {
+	if (rcRxPin < 0) return;
 	print("Setup RC\n");
-	rc.begin();
+	rc.begin(rcRxPin);
 }
 
 bool readRC() {
+	if (rcRxPin < 0) return false;
 	if (rc.read()) {
 		SBUSData data = rc.data();
 		for (int i = 0; i < 16; i++) channels[i] = data.ch[i]; // copy channels data
@@ -38,30 +43,34 @@ void normalizeRC() {
 		controls[i] = mapf(channels[i], channelZero[i], channelMax[i], 0, 1);
 	}
 	// Update control values
-	controlRoll = rollChannel >= 0 ? controls[(int)rollChannel] : NAN;
+	controlRoll = rollChannel < 0 ? 0 : controls[rollChannel];
-	controlPitch = pitchChannel >= 0 ? controls[(int)pitchChannel] : NAN;
+	controlPitch = pitchChannel < 0 ? 0 : controls[pitchChannel];
-	controlYaw = yawChannel >= 0 ? controls[(int)yawChannel] : NAN;
+	controlYaw = yawChannel < 0 ? 0 : controls[yawChannel];
-	controlThrottle = throttleChannel >= 0 ? controls[(int)throttleChannel] : NAN;
+	controlThrottle = throttleChannel < 0 ? 0 : controls[throttleChannel];
-	controlMode = modeChannel >= 0 ? controls[(int)modeChannel] : NAN;
+	controlMode = modeChannel < 0 ? NAN : controls[modeChannel]; // mode control is ineffective if not mapped
 }
 
 void calibrateRC() {
-	uint16_t zero[16];
+	if (rcRxPin < 0) {
-	uint16_t center[16];
+		print("RC_RX_PIN = %d, set the RC pin!\n", rcRxPin);
-	uint16_t max[16];
+		return;
+	}
+	uint16_t zero[16]; // for zero positions
+	uint16_t center[16]; // for center positions
+	uint16_t _[16]; // for unused data
 	print("1/8 Calibrating RC: put all switches to default positions [3 sec]\n");
 	pause(3);
-	calibrateRCChannel(NULL, zero, zero, "2/8 Move sticks [3 sec]\n...     ...\n...     .o.\n.o.     ...\n");
+	calibrateRCChannel(NULL, _, zero, "2/8 Move sticks [3 sec]\n...     ...\n...     .o.\n.o.     ...\n");
-	calibrateRCChannel(NULL, center, center, "3/8 Move sticks [3 sec]\n...     ...\n.o.     .o.\n...     ...\n");
+	calibrateRCChannel(&throttleChannel, zero, _, "3/8 Move sticks [3 sec]\n.o.     ...\n...     .o.\n...     ...\n");
-	calibrateRCChannel(&throttleChannel, zero, max, "4/8 Move sticks [3 sec]\n.o.     ...\n...     .o.\n...     ...\n");
+	calibrateRCChannel(NULL, _, center, "4/8 Move sticks [3 sec]\n...     ...\n.o.     .o.\n...     ...\n");
-	calibrateRCChannel(&yawChannel, center, max, "5/8 Move sticks [3 sec]\n...     ...\n..o     .o.\n...     ...\n");
+	calibrateRCChannel(&yawChannel, center, _, "5/8 Move sticks [3 sec]\n...     ...\n..o     .o.\n...     ...\n");
-	calibrateRCChannel(&pitchChannel, zero, max, "6/8 Move sticks [3 sec]\n...     .o.\n...     ...\n.o.     ...\n");
+	calibrateRCChannel(&pitchChannel, zero, _, "6/8 Move sticks [3 sec]\n...     .o.\n...     ...\n.o.     ...\n");
-	calibrateRCChannel(&rollChannel, zero, max, "7/8 Move sticks [3 sec]\n...     ...\n...     ..o\n.o.     ...\n");
+	calibrateRCChannel(&rollChannel, zero, _, "7/8 Move sticks [3 sec]\n...     ...\n...     ..o\n.o.     ...\n");
-	calibrateRCChannel(&modeChannel, zero, max, "8/8 Put mode switch to max [3 sec]\n");
+	calibrateRCChannel(&modeChannel, zero, _, "8/8 Put mode switch to max [3 sec]\n");
 	printRCCalibration();
 }
 
-void calibrateRCChannel(float *channel, uint16_t in[16], uint16_t out[16], const char *str) {
+void calibrateRCChannel(int *channel, uint16_t in[16], uint16_t out[16], const char *str) {
 	print("%s", str);
 	pause(3);
 	for (int i = 0; i < 30; i++) readRC(); // try update 30 times max
@@ -82,15 +91,15 @@ void calibrateRCChannel(float *channel, uint16_t in[16], uint16_t out[16], const
 		channelZero[ch] = in[ch];
 		channelMax[ch] = out[ch];
 	} else {
-		*channel = NAN;
+		*channel = -1;
 	}
 }
 
 void printRCCalibration() {
 	print("Control   Ch     Zero   Max\n");
-	print("Roll      %-7g%-7g%-7g\n", rollChannel, rollChannel >= 0 ? channelZero[(int)rollChannel] : NAN, rollChannel >= 0 ? channelMax[(int)rollChannel] : NAN);
+	print("Roll      %-7d%-7d%-7d\n", rollChannel, rollChannel < 0 ? 0 : channelZero[rollChannel], rollChannel < 0 ? 0 : channelMax[rollChannel]);
-	print("Pitch     %-7g%-7g%-7g\n", pitchChannel, pitchChannel >= 0 ? channelZero[(int)pitchChannel] : NAN, pitchChannel >= 0 ? channelMax[(int)pitchChannel] : NAN);
+	print("Pitch     %-7d%-7d%-7d\n", pitchChannel, pitchChannel < 0 ? 0 : channelZero[pitchChannel], pitchChannel < 0 ? 0 : channelMax[pitchChannel]);
-	print("Yaw       %-7g%-7g%-7g\n", yawChannel, yawChannel >= 0 ? channelZero[(int)yawChannel] : NAN, yawChannel >= 0 ? channelMax[(int)yawChannel] : NAN);
+	print("Yaw       %-7d%-7d%-7d\n", yawChannel, yawChannel < 0 ? 0 : channelZero[yawChannel], yawChannel < 0 ? 0 : channelMax[yawChannel]);
-	print("Throttle  %-7g%-7g%-7g\n", throttleChannel, throttleChannel >= 0 ? channelZero[(int)throttleChannel] : NAN, throttleChannel >= 0 ? channelMax[(int)throttleChannel] : NAN);
+	print("Throttle  %-7d%-7d%-7d\n", throttleChannel, throttleChannel < 0 ? 0 : channelZero[throttleChannel], throttleChannel < 0 ? 0 : channelMax[throttleChannel]);
-	print("Mode      %-7g%-7g%-7g\n", modeChannel, modeChannel >= 0 ? channelZero[(int)modeChannel] : NAN, modeChannel >= 0 ? channelMax[(int)modeChannel] : NAN);
+	print("Mode      %-7d%-7d%-7d\n", modeChannel, modeChannel < 0 ? 0 : channelZero[modeChannel], modeChannel < 0 ? 0 : channelMax[modeChannel]);
 }

flix/safety.ino

@@ -3,12 +3,12 @@
 
 // Fail-safe functions
 
-#define RC_LOSS_TIMEOUT 1
-#define DESCEND_TIME 10
-
 extern float controlTime;
 extern float controlRoll, controlPitch, controlThrottle, controlYaw;
 
+float rcLossTimeout = 1;
+float descendTime = 10;
+
 void failsafe() {
 	rcLossFailsafe();
 	autoFailsafe();
@@ -16,9 +16,8 @@ void failsafe() {
 
 // RC loss failsafe
 void rcLossFailsafe() {
-	if (controlTime == 0) return; // no RC at all
 	if (!armed) return;
-	if (t - controlTime > RC_LOSS_TIMEOUT) {
+	if (t - controlTime > rcLossTimeout) {
 		descend();
 	}
 }
@@ -27,7 +26,7 @@ void rcLossFailsafe() {
 void descend() {
 	mode = AUTO;
 	attitudeTarget = Quaternion();
-	thrustTarget -= dt / DESCEND_TIME;
+	thrustTarget -= dt / descendTime;
 	if (thrustTarget < 0) {
 		thrustTarget = 0;
 		armed = false;
@@ -38,8 +37,8 @@ void descend() {
 void autoFailsafe() {
 	static float roll, pitch, yaw, throttle;
 	if (roll != controlRoll || pitch != controlPitch || yaw != controlYaw || abs(throttle - controlThrottle) > 0.05) {
-		// controls changed
+		// controls changed and mode switch is not configured
-		if (mode == AUTO) mode = STAB; // regain control by the pilot
+		if (mode == AUTO && invalid(controlMode)) mode = STAB; // regain control by the pilot
 	}
 	roll = controlRoll;
 	pitch = controlPitch;

flix/time.ino

@@ -3,6 +3,8 @@
 
 // Time related functions
 
+float t = NAN; // current time, s
+float dt; // time delta with the previous step, s
 float loopRate; // Hz
 
 void step() {

flix/util.h

@@ -6,8 +6,7 @@
 #pragma once
 
 #include <math.h>
-#include <soc/soc.h>
+#include <ESP32_NOW_Serial.h>
-#include <soc/rtc_cntl_reg.h>
 
 const float ONE_G = 9.80665;
 extern float t;
@@ -35,21 +34,29 @@ 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);
-}
-
 // Trim and split string by spaces
 void splitString(String& str, String& token0, String& token1, String& token2) {
 	str.trim();
+	if (str.isEmpty()) return;
 	char chars[str.length() + 1];
 	str.toCharArray(chars, str.length() + 1);
 	token0 = strtok(chars, " ");
-	token1 = strtok(NULL, " "); // String(NULL) creates empty string
+	token1 = strtok(NULL, " ");
 	token2 = strtok(NULL, "");
+	if (token1.c_str() == NULL) token1 = "";
+	if (token2.c_str() == NULL) token2 = "";
 }
 
+// Simplified ESP-NOW Serial without tx buffering and resends
+class ESPNOWSerial : public ESP_NOW_Serial_Class {
+public:
+	using ESP_NOW_Serial_Class::ESP_NOW_Serial_Class;
+	void onSent(bool success) override {} // disable resends
+	size_t write(const uint8_t *data, size_t len) override {
+		return ESP_NOW_Peer::send(data, len); // pure send without buffering
+	}
+};
+
 // Rate limiter
 class Rate {
 public:

flix/vector.h

@@ -35,7 +35,6 @@ public:
 		z = NAN;
 	}
 
-
 	float norm() const {
 		return sqrt(x * x + y * y + z * z);
 	}
@@ -106,10 +105,23 @@ public:
 	}
 
 	static Vector rotationVectorBetween(const Vector& a, const Vector& b) {
+		float an = a.norm();
+		float bn = b.norm();
+		if (an < 1e-6 || bn < 1e-6) {
+			return Vector(0, 0, 0);
+		}
 		Vector direction = cross(a, b);
-		if (direction.zero()) {
+		if (direction.norm() < 1e-6) { // vectors are parallel
-			// vectors are opposite, return any perpendicular vector
+			if (dot(a, b) > 0) { // same direction
-			return cross(a, Vector(1, 0, 0));
+				return Vector(0, 0, 0);
+			}
+			// opposite direction
+			Vector perp = cross(a, Vector(1, 0, 0));
+			if (perp.norm() < 1e-6) {
+				perp = cross(a, Vector(0, 1, 0));
+			}
+			perp.normalize();
+			return perp * PI;
 		}
 		direction.normalize();
 		float angle = angleBetween(a, b);

flix/wifi.ino

@@ -1,45 +1,129 @@
 // Copyright (c) 2023 Oleg Kalachev <okalachev@gmail.com>
 // Repository: https://github.com/okalachev/flix
 
-// Wi-Fi support
+// Wi-Fi and ESP-NOW communication
-
-#if WIFI_ENABLED
 
 #include <WiFi.h>
 #include <WiFiAP.h>
 #include <WiFiUdp.h>
+#include <MacAddress.h>
+#include <ESP32_NOW_Serial.h>
+#include "Preferences.h"
+#include "util.h"
 
-#define WIFI_AP_MODE 1
+extern Preferences storage; // use the main preferences storage
-#define WIFI_AP_SSID "flix"
-#define WIFI_AP_PASSWORD "flixwifi"
-#define WIFI_SSID ""
-#define WIFI_PASSWORD ""
-#define WIFI_UDP_PORT 14550
-#define WIFI_UDP_REMOTE_PORT 14550
-#define WIFI_UDP_REMOTE_ADDR "255.255.255.255"
 
+const int W_DISABLED = 0, W_AP = 1, W_STA = 2, W_ESPNOW = 3;
+int wifiMode = W_AP;
+
+int wifiLongRange = 0;
+int udpLocalPort = 14550;
+int udpRemotePort = 14550;
+IPAddress udpRemoteIP = "255.255.255.255";
 WiFiUDP udp;
 
+ESPNOWSerial espnow(NULL, 0, WIFI_IF_AP);
+ESPNOWSerial espnowBroadcast(ESP_NOW.BROADCAST_ADDR, 0, WIFI_IF_AP);
+int espnowChannel = 6;
+
 void setupWiFi() {
 	print("Setup Wi-Fi\n");
-	if (WIFI_AP_MODE) {
+	WiFi.enableLongRange(wifiLongRange);
-		WiFi.softAP(WIFI_AP_SSID, WIFI_AP_PASSWORD);
+
-	} else {
+	if (wifiMode == W_AP) {
-		WiFi.begin(WIFI_SSID, WIFI_PASSWORD);
+		WiFi.softAP(storage.getString("WIFI_AP_SSID", "flix").c_str(), storage.getString("WIFI_AP_PASS", "flixwifi").c_str());
+		udp.begin(udpLocalPort);
+	} else if (wifiMode == W_STA) {
+		WiFi.begin(storage.getString("WIFI_STA_SSID", "").c_str(), storage.getString("WIFI_STA_PASS", "").c_str());
+		udp.begin(udpLocalPort);
+	} else if (wifiMode == W_ESPNOW) {
+		WiFi.mode(WIFI_AP);
+		WiFi.setChannel(espnowChannel);
+		espnow.addr(MacAddress(storage.getString("ESPNOW_PEER_MAC", "FF:FF:FF:FF:FF:FF").c_str()));
+		String key = storage.getString("ESPNOW_PEER_KEY", "");
+		espnow.setKey(key.isEmpty() ? nullptr : (const uint8_t *)key.c_str());
+		espnow.begin();
+		espnowBroadcast.begin();
 	}
-	udp.begin(WIFI_UDP_PORT);
+
+	WiFi.setSleep(false); // disable power save
 }
 
 void sendWiFi(const uint8_t *buf, int len) {
-	if (WiFi.softAPIP() == IPAddress(0, 0, 0, 0) && WiFi.status() != WL_CONNECTED) return;
+	if (espnow) {
-	udp.beginPacket(udp.remoteIP() ? udp.remoteIP() : WIFI_UDP_REMOTE_ADDR, WIFI_UDP_REMOTE_PORT);
+		espnow.write(buf, len);
+		static Rate discovery(2);
+		if (discovery) espnowBroadcast.write((const uint8_t *)"flix", 4); // broadcast message to help finding this device
+		return;
+	}
+
+	if (WiFi.softAPgetStationNum() == 0 && !WiFi.isConnected()) return;
+
+	udp.beginPacket(udpRemoteIP, udpRemotePort);
 	udp.write(buf, len);
 	udp.endPacket();
 }
 
 int receiveWiFi(uint8_t *buf, int len) {
+	if (espnow) {
+		return espnow.read(buf, len);
+	}
+
+	if (WiFi.softAPgetStationNum() == 0 && !WiFi.isConnected()) return 0;
+
 	udp.parsePacket();
+	if (udp.remoteIP()) udpRemoteIP = udp.remoteIP();
 	return udp.read(buf, len);
 }
 
-#endif
+void printWiFiInfo() {
+	if (espnow) {
+		print("Mode: ESP-NOW\n");
+		print("ESP-NOW version: %d\n", ESP_NOW.getVersion());
+		print("Max packet size: %d\n", ESP_NOW.getMaxDataLen());
+		print("MAC: %s\n", WiFi.softAPmacAddress().c_str());
+		print("Peer MAC: %s\n", MacAddress(espnow.addr()).toString().c_str());
+		print("Encrypted: %d\n", espnow.isEncrypted());
+		print("Channel: %d\n", espnow.getChannel());
+	} else if (WiFi.getMode() == WIFI_MODE_AP) {
+		print("Mode: Access Point (AP)\n");
+		print("MAC: %s\n", WiFi.softAPmacAddress().c_str());
+		print("SSID: %s\n", WiFi.softAPSSID().c_str());
+		print("Password: ***\n");
+		print("Channel: %d\n", WiFi.channel());
+		print("Clients: %d\n", WiFi.softAPgetStationNum());
+		print("IP: %s\n", WiFi.softAPIP().toString().c_str());
+		print("Remote IP: %s\n", udpRemoteIP.toString().c_str());
+	} else if (WiFi.getMode() == WIFI_MODE_STA) {
+		print("Mode: Client (STA)\n");
+		print("Connected: %d\n", WiFi.isConnected());
+		print("MAC: %s\n", WiFi.macAddress().c_str());
+		print("SSID: %s\n", WiFi.SSID().c_str());
+		print("Password: ***\n");
+		print("Channel: %d\n", WiFi.channel());
+		print("RSSI: %d dBm\n", WiFi.RSSI());
+		print("IP: %s\n", WiFi.localIP().toString().c_str());
+		print("Remote IP: %s\n", udpRemoteIP.toString().c_str());
+	} else {
+		print("Mode: Disabled\n");
+	}
+	print("MAVLink connected: %d\n", mavlinkConnected);
+}
+
+void configWiFi(int mode, const char *first, const char *second) {
+	MacAddress mac;
+	if (mode == W_AP && strlen(first) > 0 && strlen(second) >= 8) {
+		storage.putString("WIFI_AP_SSID", first);
+		storage.putString("WIFI_AP_PASS", second);
+	} else if (mode == W_STA && strlen(first) > 0 && strlen(second) >= 8) {
+		storage.putString("WIFI_STA_SSID", first);
+		storage.putString("WIFI_STA_PASS", second);
+	} else if (mode == W_ESPNOW && mac.fromString(first)) {
+		storage.putString("ESPNOW_PEER_MAC", first);
+		storage.putString("ESPNOW_PEER_KEY", strlen(second) == ESP_NOW_KEY_LEN ? second : "");
+	} else {
+		print("Invalid configuration\n");
+		return;
+	}
+	print("✓ Reboot to apply new settings\n");
+}

gazebo/Arduino.h

@@ -21,6 +21,8 @@
 #define degrees(rad) ((rad)*RAD_TO_DEG)
 
 #define constrain(amt,low,high) ((amt)<(low)?(low):((amt)>(high)?(high):(amt)))
+template<typename T> T max(T a, T b) { return a > b ? a : b; }
+template<typename T> T min(T a, T b) { return a < b ? a : b; }
 
 long map(long x, long in_min, long in_max, long out_min, long out_max) {
 	const long run = in_max - in_min;
@@ -149,7 +151,7 @@ public:
 	void setRxInvert(bool invert) {};
 };
 
-HardwareSerial Serial, Serial2;
+HardwareSerial Serial, Serial1, Serial2;
 
 class EspClass {
 public:
@@ -165,6 +167,9 @@ void delay(uint32_t ms) {
 
 bool ledcAttach(uint8_t pin, uint32_t freq, uint8_t resolution) { return true; }
 bool ledcWrite(uint8_t pin, uint32_t duty) { return true; }
+uint32_t ledcChangeFrequency(uint8_t pin, uint32_t freq, uint8_t resolution) { return freq; }
+int8_t digitalPinToAnalogChannel(uint8_t pin) { return -1; }
+uint32_t analogReadMilliVolts(uint8_t pin) { return 0; }
 
 unsigned long __micros;
 unsigned long __resetTime = 0;

gazebo/ESP32_NOW_Serial.h

@@ -0,0 +1,12 @@
+// Dummy file for the simulator
+
+class ESP_NOW_Peer {
+protected:
+	size_t send(const uint8_t *data, int len) { return 0; }
+};
+
+class ESP_NOW_Serial_Class : public ESP_NOW_Peer {
+public:
+	virtual void onSent(bool success) {};
+	virtual size_t write(const uint8_t *data, size_t len) { return 0; };
+};

gazebo/README.md

@@ -68,6 +68,9 @@ Just like the real drone, the simulator can be controlled using a USB remote con
 6. Go to the settings and enable *Virtual Joystick*. *Auto-Center Throttle* setting **should be disabled**.
 7. Use the virtual joystick to fly the drone!
 
+> [!TIP]
+> Decrease `CTL_TILT_MAX` parameter when flying using the smartphone to make the controls less sensitive.
+
 ### Control with USB remote control
 
 1. Connect your USB remote control to the machine running the simulator.

gazebo/SBUS.h

@@ -13,7 +13,7 @@ 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() {};
+	void begin(int rxpin = -1, int txpin = -1, bool inv = true, bool fast = false) {};
 	bool read() { return joystickInit(); };
 	SBUSData data() {
 		SBUSData data;

gazebo/flix.h

@@ -9,41 +9,44 @@
 #include "quaternion.h"
 #include "Arduino.h"
 #include "wifi.h"
+#include "lpf.h"
 
-#define WIFI_ENABLED 1
+extern float t, dt;
+extern float controlRoll, controlPitch, controlYaw, controlThrottle, controlMode;
+extern Vector rates;
+extern Quaternion attitude;
+extern bool landed;
+extern float motors[4];
 
-float t = NAN;
+Vector gyro, acc, imuRotation;
-float dt;
+Vector accBias, gyroBias, accScale(1, 1, 1);
-float motors[4];
+LowPassFilter<Vector> gyroBiasFilter(0);
-float controlRoll, controlPitch, controlYaw, controlThrottle = NAN;
-float controlMode = NAN;
-Vector acc;
-Vector gyro;
-Vector rates;
-Quaternion attitude;
-bool landed;
 
 // declarations
 void step();
 void computeLoopRate();
 void applyGyro();
 void applyAcc();
+void applyLevel();
 void control();
 void interpretControls();
 void controlAttitude();
 void controlRates();
 void controlTorque();
+void desaturate(float& a, float& b, float& c, float& d);
 const char* getModeName();
 void sendMotors();
+int getDutyCycle(float value);
 bool motorsActive();
 void testMotor(int n);
 void print(const char* format, ...);
 void pause(float duration);
 void doCommand(String str, bool echo);
 void handleInput();
+void setupRC();
 void normalizeRC();
 void calibrateRC();
-void calibrateRCChannel(float *channel, uint16_t zero[16], uint16_t max[16], const char *str);
+void calibrateRCChannel(int*, uint16_t[16], uint16_t[16], const char*);
 void printRCCalibration();
 void printLogHeader();
 void printLogData();
@@ -55,6 +58,7 @@ void handleMavlink(const void *_msg);
 void mavlinkPrint(const char* str);
 void sendMavlinkPrint();
 inline Quaternion fluToFrd(const Quaternion &q);
+void setupPower();
 void failsafe();
 void rcLossFailsafe();
 void descend();
@@ -73,4 +77,5 @@ void calibrateGyro() { print("Skip gyro calibrating\n"); };
 void calibrateAccel() { print("Skip accel calibrating\n"); };
 void printIMUCalibration() { print("cal: N/A\n"); };
 void printIMUInfo() {};
-Vector accBias, gyroBias, accScale(1, 1, 1);
+void printWiFiInfo() {};
+void configWiFi(bool, const char*, const char*) { print("Skip WiFi config\n"); };

gazebo/simulator.cpp

@@ -27,6 +27,7 @@
 #include "mavlink.ino"
 #include "motors.ino"
 #include "parameters.ino"
+#include "power.ino"
 #include "rc.ino"
 #include "time.ino"
 
@@ -72,6 +73,8 @@ public:
 		gyro = Vector(imu->AngularVelocity().X(), imu->AngularVelocity().Y(), imu->AngularVelocity().Z());
 		acc = this->accFilter.update(Vector(imu->LinearAcceleration().X(), imu->LinearAcceleration().Y(), imu->LinearAcceleration().Z()));
 
+		voltage = 4.2f; // dummy voltage value
+
 		readRC();
 		estimate();
 

gazebo/soc/soc.h

@@ -1,4 +1,3 @@
 // 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

@@ -11,9 +11,10 @@
 #include <sys/poll.h>
 #include <gazebo/gazebo.hh>
 
-#define WIFI_UDP_PORT 14580
+int wifiMode = 1; // mock
-#define WIFI_UDP_REMOTE_PORT 14550
+int udpLocalPort = 14580;
-#define WIFI_UDP_REMOTE_ADDR "255.255.255.255"
+int udpRemotePort = 14550;
+const char *udpRemoteIP = "255.255.255.255";
 
 int wifiSocket;
 
@@ -22,22 +23,22 @@ void setupWiFi() {
 	sockaddr_in addr; // local address
 	addr.sin_family = AF_INET;
 	addr.sin_addr.s_addr = INADDR_ANY;
-	addr.sin_port = htons(WIFI_UDP_PORT);
+	addr.sin_port = htons(udpLocalPort);
 	if (bind(wifiSocket, (sockaddr *)&addr, sizeof(addr))) {
-		gzerr << "Failed to bind WiFi UDP socket on port " << WIFI_UDP_PORT << std::endl;
+		gzerr << "Failed to bind WiFi UDP socket on port " << udpLocalPort << std::endl;
 		return;
 	}
 	int broadcast = 1;
 	setsockopt(wifiSocket, SOL_SOCKET, SO_BROADCAST, &broadcast, sizeof(broadcast)); // enable broadcast
-	gzmsg << "WiFi UDP socket initialized on port " << WIFI_UDP_PORT << " (remote port " << WIFI_UDP_REMOTE_PORT << ")" << std::endl;
+	gzmsg << "WiFi UDP socket initialized on port " << udpLocalPort << " (remote port " << udpRemotePort << ")" << 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 = inet_addr(WIFI_UDP_REMOTE_ADDR);
+	addr.sin_addr.s_addr = inet_addr(udpRemoteIP);
-	addr.sin_port = htons(WIFI_UDP_REMOTE_PORT);
+	addr.sin_port = htons(udpRemotePort);
 	sendto(wifiSocket, buf, len, 0, (sockaddr *)&addr, sizeof(addr));
 }
 

tools/espnow-proxy/README.md

@@ -0,0 +1,3 @@
+# ESPNOW-proxy
+
+Proxy sketch for using ESP-NOW connection with Flix drone.

tools/espnow-proxy/espnow-proxy.ino

@@ -0,0 +1,88 @@
+// Copyright (c) 2026 Oleg Kalachev <okalachev@gmail.com>
+// Repository: https://github.com/okalachev/flix
+
+// Proxy for ESP-NOW connection
+
+#include <vector>
+#include <WiFi.h>
+#include <ESP32_NOW_Serial.h>
+#include <MacAddress.h>
+#include <MAVLink.h>
+#include <Preferences.h>
+#include "../../flix/util.h"
+
+const int CHANNEL = 6;
+char key[ESP_NOW_KEY_LEN + 1] = {0}; // with trailing null
+
+Preferences storage;
+
+std::vector<ESPNOWSerial *> peers;
+
+void onNewPeer(const esp_now_recv_info_t *info, const uint8_t *data, int len, void *arg) {
+	if (len != 4 || memcmp(data, "flix", 4) != 0) return; // check if discovery message
+
+	Serial.printf("New peer: " MACSTR "\n", MAC2STR(info->src_addr));
+	ESPNOWSerial *link = new ESPNOWSerial(info->src_addr, CHANNEL, WIFI_IF_AP);
+	link->begin();
+	link->setKey((const uint8_t *)key);
+	peers.push_back(link);
+}
+
+void setup() {
+	Serial.begin(115200);
+	WiFi.mode(WIFI_AP);
+	WiFi.setSleep(false);
+	WiFi.setChannel(CHANNEL);
+
+	ESP_NOW.onNewPeer(onNewPeer, NULL);
+	ESP_NOW.begin();
+
+	storage.begin("espnow-proxy");
+	if (!storage.isKey("key")) {
+		generateRandomKey();
+		storage.putString("key", key);
+	}
+	strcpy(key, storage.getString("key").c_str());
+
+	// Discover the first peer
+	while (peers.empty()) {
+		Serial.printf("espnow %s %s\n", WiFi.softAPmacAddress().c_str(), key);
+		delay(500);
+	}
+}
+
+void generateRandomKey() {
+	const char chars[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789!@#$%^&*-_+=";
+	for (int i = 0; i < ESP_NOW_KEY_LEN; i++) {
+		key[i] = chars[random(0, strlen(chars))];
+	}
+}
+
+void loop() {
+	uint8_t buf[5000];
+
+	// Send from Serial to ESP-NOW
+	while (Serial.available() > 0) {
+		int b = Serial.read();
+		if (b < 0) {
+			break;
+		}
+
+		mavlink_message_t msg;
+		mavlink_status_t status;
+		if (mavlink_parse_char(MAVLINK_COMM_0, (uint8_t)b, &msg, &status)) {
+			int len = mavlink_msg_to_send_buffer(buf, &msg);
+			for (ESPNOWSerial *link : peers) {
+				link->write(buf, len);
+			}
+		}
+	}
+
+	// Send from ESP-NOW to Serial
+	for (ESPNOWSerial *link : peers) {
+		int len = link->read(buf, sizeof(buf));
+		if (len > 0) {
+			Serial.write(buf, len);
+		}
+	}
+}

tools/example.py

@@ -10,6 +10,7 @@ print('Connected:', flix.connected)
 print('Mode:', flix.mode)
 print('Armed:', flix.armed)
 print('Landed:', flix.landed)
+print('Voltage:', flix.voltage, 'V')
 print('Rates:', *[f'{math.degrees(r):.0f}°/s' for r in flix.rates])
 print('Attitude:', *[f'{math.degrees(a):.0f}°' for a in flix.attitude_euler])
 print('Motors:', flix.motors)
@@ -23,11 +24,11 @@ print('> imu')
 print(flix.cli('imu'))
 
 print('=== Get parameter...')
-pitch_p = flix.get_param('PITCH_P')
+pitch_p = flix.get_param('CTL_P_P')
-print('PITCH_P = ', pitch_p)
+print('CTL_P_P = ', pitch_p)
 
 print('=== Set parameter...')
-flix.set_param('PITCH_P', pitch_p)
+flix.set_param('CTL_P_P', pitch_p)
 
 print('=== Wait for gyro update...')
 print('Gyro: ', flix.wait('gyro'))

tools/grab_log.py

@@ -13,7 +13,7 @@ lines = []
 
 print('Downloading log...')
 count = 0
-dev.write('log\n'.encode())
+dev.write('log dump\n'.encode())
 while True:
     line = dev.readline()
     if not line:

tools/log.py

@@ -43,6 +43,7 @@ records = [record for record in records if record[0] != 0]
 
 print(f'Received records: {len(records)}')
 
+os.makedirs(f'{DIR}/log', exist_ok=True)
 log = open(f'{DIR}/log/{datetime.datetime.now().isoformat()}.csv', 'wb')
 log.write(header.encode() + b'\n')
 for record in records:

tools/pyflix/README.md

@@ -1,8 +1,8 @@
 # Flix Python library
 
-The Flix Python library allows you to remotely connect to a Flix quadcopter. It provides access to telemetry data, supports executing CLI commands, and controlling the drone's flight.
+The Flix Python library allows you to remotely connect to a Flix quadcopter. It provides access to telemetry data, supports executing console commands, and controlling the drone's flight.
 
-To use the library, connect to the drone's Wi-Fi. To use it with the simulator, ensure the script runs on the same local network as the simulator.
+To use the library, connect to the drone's Wi-Fi. To use it with the simulator, ensure the script runs on the same network as the simulator.
 
 ## Installation
 
@@ -24,24 +24,25 @@ pip install pyflix
 The API is accessed through the `Flix` class:
 
 ```python
-from flix import Flix
+from pyflix import Flix
 flix = Flix()  # create a Flix object and wait for connection
 ```
 
 ### Telemetry
 
-Basic telemetry is available through object properties. The properties names generally match the corresponding variables in the firmware itself:
+Basic telemetry is available through object properties. The property names generally match the corresponding variables in the firmware code:
 
 ```python
 print(flix.connected)       # True if connected to the drone
 print(flix.mode)            # current flight mode (str)
 print(flix.armed)           # True if the drone is armed
 print(flix.landed)          # True if the drone is landed
+print(flix.voltage)         # battery voltage (NaN - unknown, ~0 - USB powered)
 print(flix.attitude)        # attitude quaternion [w, x, y, z]
 print(flix.attitude_euler)  # attitude as Euler angles [roll, pitch, yaw]
 print(flix.rates)           # angular rates [roll_rate, pitch_rate, yaw_rate]
 print(flix.channels)        # raw RC channels (list)
-print(flix.motors)          # motors outputs (list)
+print(flix.motors)          # motor outputs (list)
 print(flix.acc)             # accelerometer output (list)
 print(flix.gyro)            # gyroscope output (list)
 ```
@@ -92,36 +93,37 @@ Full list of events:
 |-----|-----------|----------------|
 |`connected`|Connected to the drone||
 |`disconnected`|Connection is lost||
-|`armed`|Armed state update|Armed state (*bool*)|
+|`armed`|Armed state update|Armed state *(bool)*|
-|`mode`|Flight mode update|Flight mode (*str*)|
+|`mode`|Flight mode update|Flight mode *(str)*|
-|`landed`|Landed state update|Landed state (*bool*)|
+|`landed`|Landed state update|Landed state *(bool)*|
-|`print`|The drone sends text to the console|Text|
+|`voltage`|Battery voltage update|Voltage *(float)*|
-|`attitude`|Attitude update|Attitude quaternion (*list*)|
+|`print`|The drone prints text to the console|Text|
-|`attitude_euler`|Attitude update|Euler angles (*list*)|
+|`attitude`|Attitude update|Attitude quaternion *(list)*|
-|`rates`|Angular rates update|Angular rates (*list*)|
+|`attitude_euler`|Attitude update|Euler angles *(list)*|
-|`channels`|Raw RC channels update|Raw RC channels (*list*)|
+|`rates`|Angular rates update|Angular rates *(list)*|
-|`motors`|Motors outputs update|Motors outputs (*list*)|
+|`channels`|Raw RC channels update|Raw RC channels *(list)*|
-|`acc`|Accelerometer update|Accelerometer output (*list*)|
+|`motors`|Motor outputs update|Motor outputs *(list)*|
-|`gyro`|Gyroscope update|Gyroscope output (*list*)|
+|`acc`|Accelerometer update|Accelerometer output *(list)*|
+|`gyro`|Gyroscope update|Gyroscope output *(list)*|
 |`mavlink`|Received MAVLink message|Message object|
 |`mavlink.<message_name>`|Received specific MAVLink message|Message object|
 |`mavlink.<message_id>`|Received specific MAVLink message|Message object|
 |`value`|Named value update (see below)|Name, value|
-|`value.<name>`|Specific named value update (see bellow)|Value|
+|`value.<name>`|Specific named value update (see below)|Value|
 
 > [!NOTE]
-> Update events trigger on every new data from the drone, and do not mean the value has changed.
+> Update events trigger on every new piece of data from the drone, and do not mean the value has changed.
 
-### Common methods
+### Basic methods
 
 Get and set firmware parameters using `get_param` and `set_param` methods:
 
 ```python
-pitch_p = flix.get_param('PITCH_P')  # get parameter value
+pitch_p = flix.get_param('CTL_P_P')  # get parameter value
-flix.set_param('PITCH_P', 5)         # set parameter value
+flix.set_param('CTL_P_P', 5)         # set parameter value
 ```
 
-Execute console commands using `cli` method. This method returns command response:
+Execute console commands using `cli` method. This method returns the command response:
 
 ```python
 imu = flix.cli('imu')    # get detailed IMU data
@@ -169,10 +171,10 @@ Setting angular rates target:
 flix.set_rates([0.1, 0.2, 0.3], 0.6)  # set target roll rate, pitch rate, yaw rate and thrust
 ```
 
-You also can control raw motors outputs directly:
+You also can control raw motor outputs directly:
 
 ```python
-flix.set_motors([0.5, 0.5, 0.5, 0.5])  # set motors outputs in range [0, 1]
+flix.set_motors([0.5, 0.5, 0.5, 0.5])  # set motor outputs in range [0, 1]
 ```
 
 In *AUTO* mode, the drone will arm automatically if the thrust is greater than zero, and disarm if thrust is zero. Therefore, to disarm the drone, set thrust to zero:
@@ -186,7 +188,7 @@ The following methods are in development and are not functional yet:
 * `set_position` — set target position.
 * `set_velocity` — set target velocity.
 
-To exit from *AUTO* mode move control sticks and the drone will switch to *STAB* mode.
+To exit *AUTO* mode move control sticks and the drone will switch to *STAB* mode.
 
 ## Usage alongside QGroundControl
 
@@ -277,7 +279,3 @@ logger = logging.getLogger('flix')
 logger.setLevel(logging.DEBUG)  # be more verbose
 logger.setLevel(logging.WARNING)  # be less verbose
 ```
-
-## Stability
-
-The library is in development stage. The API is not stable.

tools/pyflix/flix.py

@@ -5,6 +5,7 @@
 
 import os
 import time
+import math
 from queue import Queue, Empty
 from typing import Optional, Callable, List, Dict, Any, Union, Sequence
 import logging
@@ -17,7 +18,7 @@ from pymavlink.dialects.v20 import common as mavlink
 logger = logging.getLogger('flix')
 if not logger.hasHandlers():
     handler = logging.StreamHandler()
-    handler.setFormatter(logging.Formatter('%(name)s - %(levelname)s - %(message)s'))
+    handler.setFormatter(logging.Formatter('%(name)s: %(message)s'))
     logger.addHandler(handler)
     logger.setLevel(logging.INFO)
 
@@ -26,6 +27,7 @@ class Flix:
     mode: str = ''
     armed: bool = False
     landed: bool = False
+    voltage: float = math.nan
     attitude: List[float]
     attitude_euler: List[float]  # roll, pitch, yaw
     rates: List[float]
@@ -40,7 +42,7 @@ class Flix:
 
     _connection_timeout = 3
     _print_buffer: str = ''
-    _modes = ['MANUAL', 'ACRO', 'STAB', 'AUTO']
+    _modes = ['RAW', 'ACRO', 'STAB', 'AUTO']
 
     def __init__(self, system_id: int=1, wait_connection: bool=True):
         if not (0 <= system_id < 256):
@@ -68,7 +70,7 @@ class Flix:
         self._heartbeat_thread.start()
         if wait_connection:
             self.wait('mavlink.HEARTBEAT')
-            time.sleep(0.2) # give some time to receive initial state
+            time.sleep(0.6) # give some time to receive initial state
 
     def _init_state(self):
         self.attitude = [1, 0, 0, 0]
@@ -138,7 +140,7 @@ class Flix:
         while True:
             try:
                 msg: Optional[mavlink.MAVLink_message] = self.connection.recv_match(blocking=True)
-                if msg is None:
+                if msg is None or msg.get_srcSystem() != self.system_id:
                     continue
                 self._connected()
                 msg_dict = msg.to_dict()
@@ -185,11 +187,16 @@ class Flix:
             self._trigger('motors', self.motors)
 
         if isinstance(msg, mavlink.MAVLink_scaled_imu_message):
-            self.acc = self._mavlink_to_flu([msg.xacc / 1000, msg.yacc / 1000, msg.zacc / 1000])
+            ONE_G = 9.80665
+            self.acc = self._mavlink_to_flu([msg.xacc * ONE_G / 1000, msg.yacc * ONE_G / 1000, msg.zacc * ONE_G / 1000])
             self.gyro = self._mavlink_to_flu([msg.xgyro / 1000, msg.ygyro / 1000, msg.zgyro / 1000])
             self._trigger('acc', self.acc)
             self._trigger('gyro', self.gyro)
 
+        if isinstance(msg, mavlink.MAVLink_battery_status_message):
+            self.voltage = msg.voltages[0] / 1000
+            self._trigger('voltage', self.voltage)
+
         if isinstance(msg, mavlink.MAVLink_serial_control_message):
             # new chunk of data
             text = bytes(msg.data)[:msg.count].decode('utf-8', errors='ignore')

tools/pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "pyflix"
-version = "0.9"
+version = "0.15"
 description = "Python API for Flix drone"
 authors = [{ name="Oleg Kalachev", email="okalachev@gmail.com" }]
 license = "MIT"