madflight

ESP32 / RP2040 / STM32 Arduino Flight Controller

Miscellaneous

rp2040

stm32

flight-controller

esp32

Manless Aerial Device

This is an Arduino library to build ESP32 / ESP32-S3 / RP2350 / RP2040 / STM32 flight controllers. A functional DIY flight controller can be build for under $10 from readily available development boards and sensor breakout boards. Ideal if you want to try out new flight control concepts, without first having to setup a build environment and without having to read through thousands lines of code to find the spot where you want to change something.

Quadcopter.ino is a 1000 line demo program for a quadcopter. It has been flight tested on ESP32, ESP32-S3, RP2040, and STM32F405 microcontrollers with the Arduino IDE. The program can be easily adapted to control your plane or VTOL craft. The source code has extensive documentation explaning what the settings and functions do.

madflight RP2040 flight controller madflight drone madflight ESP32 flight controller

Feedback is Welcome

I enjoy hacking with electronics and I'm attempting to write some decent code for this project. If you enjoy it as well, please leave some feedback in the form of Stars, Issues, Pull Requests, or Discussions. Thanks!

Documentation

For full documention see madflight.com and the source code itself.

Quick Start

Required Hardware
Getting Started
Safety First
ESP32 / ESP32-S3 Setup and Pinout
RP2350 / RP2040 Setup and Pinout
STM32 Setup and Pinout
Connecting the IMU Sensor
Software Design
Changes from dRehmFlight
Flight Controllers on Github
Disclaimer

Required Hardware

Development board:
- RP2350 RP2040 (e.g. Raspberry Pi Pico 2)
- or ESP32/ESP32-S3 (e.g. Espressiv DevKitC)
- or STM32 (e.g. Black Pill or a commercial flight controller)
SPI IMU sensor (BMI270, MPU9250, MP6500, or MPU6000), if not available then use an I2C IMU sensor (MPU6050 or MPU9150)
RC Receiver: ELRS, CRSF, SBUS, DMSX, or PPM
BEC or DC-DC converter to power your board from a battery
ESC (OneShot125 or 50-490Hz PWM) and/or servos (50-490Hz PWM)

Optional Hardware

GPS Module (Serial)
Barometer (I2C BMP280, MS5611)
Magnetometer (I2C QMC5883L)
Current/Voltage Sensor (ADC or I2C INA226)
Optical Flow Sensor (I2C)

Getting Started

Install the Arduino madflight library
Open example Quadcopter.ino in the Arduino IDE.
Setup the USER-SPECIFIED DEFINES section
If you're not using a default pinout (see below) then setup your board pinout in the BOARD section.
Connect your IMU (gyro/acceleration) sensor as shown below.
Upload Quadcopter.ino to your board. Connect the Serial Monitor at 115200 baud and check the messages. Type help to see the available CLI commands.
Use CLI print commands like pimu, pgyro, proll to Check that IMU sensor and AHRS are working correctly.
IMPORTANT: Use CLI calimu and calmag to calibate the sensors.
Connect radio receiver to your development board according to the configured pins.
Review the RC RECEIVER CONFIG section. Either match you RC equipment to the settings, or change the settings to match your RC equipment.
Check your radio setup: Use CLI ppwm and pradio to show pwm and scaled radio values.
Connect motors (no props) and battery and check that motor outputs are working correctly. For debugging, use CLI pmot to show motor output.
Mount props, go to an wide open space, and FLY!

Safety First!!!

By default madflight has these safety features enabled:

Motors only rotate when armed.
Arming Procedure: set throttle low then flip the arm switch from disarmed to armed.
Kill Switch: when the arm switch is in the disarm position, disarm and stop motors until re-armed.
Failsafe: when radio connection is lost, disarm and stop motors until re-armed.
Armed Low Throttle: motors run at low speed, to give visible armed indication.
LED armed/disarmed indicator.

ESP32 / ESP32-S3 Setup and Pinout

madflight works with Arduino-ESP32 v3.x.x

madflight v1.1.2 and earlier works with Arduino-ESP32 v2.x.x

Dual Core / FPU / FreeRTOS

ESP32 and ESP32-S3 have dual core CPU, but single core FPU. ESP-IDF implementation limits float usage to a single core, and float can not be used in interrupts. FreeRTOS is always enabled and a watchdog limits interrupt execution time.

madflight uses float and is therefor limited to single core operation. The IMU loop runs as a high priorty task, triggered by the IMU interrupt.

I2C

Arduino-ESP32 v2.0.17 has an I2C bug which causes the bus to hang for 1 second after a failed read, which can happen a couple times per minute. This makes Wire I2C for IMU not a real option...

A workaround is to use #define USE_ESP32_SOFTWIRE which enables software I2C, but this does not work well with all sensors.

(!) So, until a better I2C solution is available: use an SPI IMU sensor on ESP32.

NOTE: as of June 2024 this bug is apparently fixed, but not yet confirmed with madflight.

Pinout ESP32

This is the default pinout for ESP32. It is optimized for the Espressiv ESP32 DevKitC (38 pin) board. This pinout is defined in madflight_board_default_ESP32.h, but can be modified with #define HW_PIN_XXX in your program.

Function	GPIO	Board	GPIO	Function
3V3 out	3V3	Antenna side	GND	GND
reset button	EN		23	I2C_SDA
SPI_MISO	VP 36 input only		22	I2C_SCL
IMU_EXTI	VN 39 input only		1 TX	USB Serial Debug TX
BAT_V	34 input only		3 RX	USB Serial Debug RX
RCIN_RX	35 input only		21	SPI_MOSI
RCIN_TX	32		GND	GND
PWM1	33		19	SPI_SCLK
PWM2	25		18	IMU_CS
PWM3	26		strap 5	GPS_TX
PWM4	27		17	GPS_RX
PWM5	14		16	PWM11
PWM6	12		4	PWM10
GND	GND		boot 0	PWM9
PWM7	13		strap 2	LED
nc	D2 9 flash		strap 15	PWM8
nc	D3 10 flash		flash 8 D1	nc
nc	CMD 11 flash		flash 7 D0	nc
5V input (*)	5V	USB connector	flash 6 CLK	nc

Note: During boot the input voltage levels (pull up/pull down) on strap pins have a configuration function, therefor these pins are used as output only.

(*) 5V input via diode from BEC. Without a diode take care not connect USB and the battery at the same time!

Pinout ESP32-S3

This is the default pinout for ESP32-S3. It is optimized for the Espressiv ESP32-S3 DevKitC-1 (44 pin) board. This pinout is defined in madflight_board_default_ESP32-S3.h, but can be modified with #define HW_PIN_XXX in your program.

Function	GPIO	Board	GPIO	Function
3V3 out	3V3	Antenna side	G	GND
3V3 out	3V3		43	TX serial debug UART port
reset button	RST		44	RX serial debug UART port
PWM1	4		1	-
PWM2	5		2	-
PWM3	6		42	-
PWM4	7		41	-
PWM5	15		40	-
PWM6	16		39	-
RCIN_TX	17		38	LED
RCIN_RX	18		37	-
I2C_SDA	8		36	-
GPS_RX	3		35	-
GPS_TX	46		0	boot button
I2C_SCL	9		45	-
IMU_CS	10		48	RGB_LED
SPI_MOSI	11		47	-
MISO	12		21	-
SCLK	13		20	USB_D+ (serial debug alternate)
IMU_EXTI	14		19	USB_D- (serial debug alternate)
5V in (*)	5V		G	GND
GND	G	USB connector	G	GND

(*) 5V input via diode from BEC. Without a diode take care not connect USB and the battery at the same time!

RP2350 / RP2040 Setup and Pinout

madflight works with arduino-pico v4.x.x

Dual Core / FPU / FreeRTOS

RP2350 (Pico2) has dual core, dual FPU, but no FreeRTOS (arduino pico v4.0.1)

RP2040 (Pico) has dual core, no FPU, and FreeRTOS is optional.

madflight uses float and is much happier with RP2350 over RP2040.

madflight on RP2040 uses FreeRTOS and executes the 1000Hz IMU loop on the second core, which is 80% loaded at default 133MHz CPU speed. You can overclock the CPU to get some more headroom.

PWM

Consecutive even/odd PWM pins (e.g. pins 2,3 or 10,11) share the same timer and have the same frequency.

Serial

madflight uses a custom high performance SerialIRQ library.

Pinout Raspberry Pi Pico / Pico2

This is the default pinout for RP2040. It is optimized for the Raspberry Pi Pico (40 pin) board. This pinout is defined in madflight_board_default_RP2040.h, but can be modified with #define HW_PIN_XXX in your program.

Function	GPIO	Board	GPIO	Function
RCIN_TX	0	USB connector	VBUS	nc
RCIN_RX	1		VSYS	5V input via diode (*)
GND	GND		GND	GND
PWM1	2		EN	nc
PWM2	3		3.3V out	3V3
PWM3	4		VREF	nc
PWM4	5		28_A2	BAT_V
GND	GND		GND	GND
PWM5	6		27_A1	-
PWM6	7		26_A0	-
GPS_TX	8		RUN	reset button to GND
GPS_RX	9		22	IMU_EXTI
GND	GND		GND	GND
PWM7	10		21	I2C_SCL
PWM8	11		20	I2C_SDA
PWM9	12		19	SPI_MOSI
PWM10	13		18	SPI_SCLK
GND	GND		GND	GND
PWM11	14		17	IMU_CS
PWM12	15	JTAG pins	16	SPI_MISO

(*) 5V input via diode from BEC. Without a diode take care not connect USB and the battery at the same time!

Pinout RP2040-Zero

This pinout is optimized for the RP2040-Zero (21 pin) board. This pinout is defined in madflight_board_RP2040-Zero.h, but can be modified with #define HW_PIN_XXX in your program.

Function	GPIO	Board	GPIO	Function
5V input (*)	5V	USB connector	0	RCIN_TX
GND	GND		1	RCIN_RX
3V3 out	3V3		2	PWM1
-	29		3	PWM2
BAT_V	28		4	PWM3
I2C1_SCL	27		5	PWM4
I2C1_SDA	26		6	PWM5
IMU_EXTI	15		7	PWM6
	14		8	GPS_TX

			9	GPS_RX
			10	SPI1_SCLK
			11	SPI1_MISO
			12	SPI1_MOSI
			13	IMU_CS

(*) 5V input via diode from BEC. Without a diode take care not connect USB and the battery at the same time!

STM32 Setup and Pinout

madflight works with stm32duino Arduino Core for STM32 v2.x.x

Dual Core / FPU / FreeRTOS

Most supported STM32 targets have a single cores with FPU. FreeRTOS support optional.

madflight runs the IMU loop in interrupt context.

Pinout STM32 Of-the-shelf Flight Controllers

In the src directory you'll find 400+ Betaflight configuration files for commercial flight controllers. Include the madflight_board_betaflight_XXX.h header file of your board, and in your program set '#define HW_USE_XXX' to match your board.

Pinout STM32 Black Pill

This is the default pinout for STM32. It is optimized for the WeAct STM32F411 Black Pill (40 pin) board. This pinout is defined in madflight_board_default_STM32.h, but can be modified with #define HW_PIN_XXX in your program.

Function	GPIO	Board	GPIO	Function
nc	VB	SWD pins	3V3	3V3 out
LED	C13		G	GND
-	C14		5V	5V input (*)
-	C15		B9	PWM10(t4)
nc	R		B8	PWM9(t4)
-	A0		B7	I2C_SCL
-	A1		B6	I2C_SDA
GPS_TX	A2		B5	PWM8(t3)
GPS_RX	A3		B4	PWM7(t3)
IMU_CS	A4		B3	RCIN_RX
SPI_SCLK	A5		A15	RCIN_TX
SPI_MISO	A6		A12	USB_DP
SPI_MOSI	A7		A11	USB_DN
BAT_I	B0		A10	PWM6(t1)
BAT_V	B1		A9	PWM5(t1)
-	B2		A8	PWM4(t1)
IMU_EXTI	B10		B15	PWM3(t1)
3V3 out	3V3		B14	PWM2(t1)
GND	G		B13	PWM1(t1)
5V input (*)	5V	USB connector	B12	-

Internally connected: C13 - LED, A0 - key button

PWM1-6 are connected to timer1, PWM7-8 to timer3 and PWM9-10 to timer4. PWM pins connected to the same timer operate at the same frequency.

(*) 5V input via diode from BEC. Without a diode take care not connect USB and the battery at the same time!

Connecting the IMU Sensor

SPI sensor: (highly recommended over I2C)

  Sensor       Dev Board
SCL/SCLK <---> SPI_SCLK
 SDA/SDI <---> SPI_MOSI
 ADD/SDO <---> SPI_MISO
     NCS <---> IMU_CS
     INT <---> IMU_EXTI
     VCC <---> 3V3
     GND <---> GND

I2C sensor:

  Sensor       Dev Board
     SCL <---> I2C_SCL 
     SDA <---> I2C_SDA
     INT <---> IMU_EXTI
     VCC <---> 3V3
     GND <---> GND

Software Design

Keep it simple!!!
Forked from dRehmFlight
Coded primarily for readability, then for speed and code size.
No external dependencies, all modules are included in the src/madflight directory.
The madflight flight controller runs standard setup() and loop().
It mainly uses plain Arduino functionality: Serial, Wire, and SPI. This makes it possible to have one code base for very different microcontroller platforms.
Hardware platform specific libraries are used for PWM and to work around issues in the standard Arduino libraries.
madflight can fairly easily ported to other 32 bit microcontrollers that support the Arduino framework. Also porting to other build environments like PlatformIO or CMake should not be a huge effort.
The following modules are used:
- imu Inertial Measurement Unit, retrieves accelerometer, gyroscope, and magnetometer sensor data
- ahrs Attitude Heading Reference System, estimates roll, yaw, pitch
- rcin RC INput, retrieves RC receiver data
- control PID controller and output mixer
- out Output to motors and servos
- mag Magnetometer (external)
- baro Barometer
- gps GPS receiver
- bb Black Box data logger
- cli Command Line Interface for debugging, configuration and calibration
- cfg Read and save configuration to flash
- hw Hardware specific code for STM32, RP2040 and ESP32
Most modules are interfaced through a global object, for example the imu object has property imu.gx which is the current gyro x-axis rate in degrees per second for the selected IMU chip.
For a quick overview of the objects, see header src/madflight/interfaces.h which defines the module interfaces.
The module implementations are in subdirectories of the src/madflight directory. Here you find the module header file, e.g. src/madflight/imu/imu.h. In the extras directory your find test programs for the modules, e.g. extras/TestMadflight/imu.ino.
The module files are usually header only, that is, the header also includes the implemention.

Changes from dRehmFlight

Add support for RP2040, RP2350, ESP32, ESP32-S3, and STM32
Dropped Teensy support, but could be re-added by creating a hw_TEENSY.h file. (I just don't have the hardware to test on)
Moved all hardware specific code to hw_XXX.h and added hardware specific libraries
Reduced the number of global variables
Oneshot is implemented as PWM up to 3.9kHz
New libs for IMU sensors
Changed arming logic
Loop rate set to 1kHz to match IMU sensor rate
Interrupt driven IMU operation, not setup/loop

Flight Controllers on Github

In (approximate) increasing order of complexity.

Flight Controller	Features	Development Environment	Microcontroller
drone-flight-controller	Single 700 line ino file, no libs	Arduino	ATmega328P
dRehmFlight	Quad, Plane, VTOL	Arduino	Arduino Teensy 4
madflight	Quad, Plane, VTOL, based on dRehmFlight	Arduino	ESP32, RP2040, and STM32
esp-fc	FPV Quad	PlatformIO	ESP32
Crazyflie	FPV Quad		STM32F405
esp-drone	FPV Quad, based on Crazyflie		ESP32
Betaflight	FPV Quad, based on cleanflight		STM32 F4/F7/H7
EmuFlight	Multi-rotor, based on cleanflight		STM32 F4/F7
inav	Plane, based on cleanflight		STM32 F4/F7/H7
Ardupilot	Quad, Plane, VTOL	Linux waf	STM32 F4/F7/H7 or Linux based
PX4-Autopilot	Quad, Plane, VTOL		STM32 F4/F7/H7

Disclaimer

This code is a shared, open source flight controller for small micro aerial vehicles and is intended to be modified to suit your needs. It is NOT intended to be used on manned vehicles. I do not claim any responsibility for any damage or injury that may be inflicted as a result of the use of this code. Use and modify at your own risk. More specifically put:

THIS SOFTWARE IS PROVIDED BY THE CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.