Manless Aerial Device

This is a 1000 line Arduino ESP32 / RP2040 / STM32 flight controller, forked from dRehmFlight. 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.

madflight/madflight.ino is a demo program for a quadcopter, but can be easily adapted to control your plane or VTOL craft. The source code has extensive documentation explaning what the settings and functions do.

Flight tested on ESP32, RP2040, and STM32F405 microcontrollers with the Arduino IDE. It mainly uses plain Arduino functionality: Serial, Wire, and SPI. One custom hardware dependent library is used for PWM. Therefor, it 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.

Required Hardware

• Development board:
  • RP2040 (e.g. Raspberry Pi Pico)
  • or ESP32 (e.g. Espressiv DevKitC)
  • or STM32 (e.g. Black Pill or a 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

0. Open madflight/madflight.ino in the Arduino IDE.
1. Setup the USER-SPECIFIED DEFINES section in the main code, and configure the pins in hw_XXX.h (see below for default pinouts)
2. Connect your IMU (gyro/acceleration) sensor as shown below.
3. Compile and upload madflight. Connect the Serial Monitor at 115200 baud and check the messages. Type 'help' to see the available CLI commands.
4. Check that IMU sensor and AHRS are working correctly: use CLI print commands to show gyro, accelerometer, magnetometer and roll/pitch/yaw.
5. Use CLI to calibate the sensor.
6. Connect radio receiver to your development board according to the configured pins.
7. Edit the RC RECEIVER CONFIG section in the main code. Either match you RC equipment to the settings, or change the settings to match your RC equipment.
8. Check your radio setup: Use CLI print commands to show pwm and scaled radio values.
9. Connect motors (no props) and battery and check that motor outputs are working correctly. For debugging, use CLI to show motor output.
10. 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.

Feedback is Welcome

I enjoy hacking around 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!

Software Design

• Keep it simple!!!
• No external dependencies, all module libraries included in src directory.
• Coded for readability, not for speed or smallest size.
• The flight controller madflight.ino runs standard setup() and loop().
• The madflight.ino uses the following modules:
  • loop Main loop control
  • 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 imu.gx is the current gyro x-axis rate in degrees per second for the selected IMU chip.
• The header src/interfaces.h defines the module interfaces.
• The module implementations are in subdirectories of the src directory. Here you find the module header file, e.g. src/imu/imu.h. There might also be an .ino module test program, e.g. src/imu/imu.ino.
• The module files are usually header only, that is, the header also includes the implemention.

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

Default Pinout for ESP32 DevKitC (38 pin)

This pinout can be configured as needed in hw_ESP32.h

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 in (*)	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!

Default Pinout for Raspberry Pi Pico (40 pin)

This pinout can be configured as needed in hw_RP2040.h

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

Default Pinout for WeActStudio STM32F411 Black Pill (40 pin)

This pinout can be configured as needed in hw_STM32.h

Function	GPIO	Board	GPIO	Function
-	VB	SWD pins	3V3	-
LED	C13		G	-
FREE	C14		5V	5V input (*)
FREE	C15		B9	PWM10(t4)
-	R		B8	PWM9(t4)
FREE	A0		B7	I2C_SCL
FREE	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)
FREE	B2		A8	PWM4(t1)
IMU_EXTI	B10		B15	PWM3(t1)
-	3V3		B14	PWM2(t1)
-	G		B13	PWM1(t1)
-	5V	USB connector	B12	FREE

Board: LED: C13, key button: A0

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!

Changes from dRehmFlight

• Add support for RP2040, ESP32, 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 by default, but setup/loop still possible

Flight Controllers on Github

In increasing order of complexity.

• lobodol/drone-flight-controller Arduino ATmega328P, single 700 line ino file, no libs
• dRehmFlight Arduino Teensy 4
• madflight Arduino RP2040, ESP32, and STM32
• Crazyflie STM32F405
• esp-drone ESP32 (forked from Crazyflie)
• Betaflight STM32 F4/F7/H7
• inav STM32 F4/F7/H7
• Ardupilot STM32 F4/F7/H7 or Linux based

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.

Logo image copyright (c) 1975 Deutsches MAD Magazine. This project is not associated with MAD Magazine.