STM32 Flight controller

Implementing a flight controller for a small quadcopter. UAV is controlled through ELRS transmitter.

What's done:

• single roll/pitch PID control loop, stabilization using gyroscope (accro mode) readings.
• double roll/pitch PID control loop, stabilization using accelerometer/gyroscope readings.
• yaw stabilization using gyroscope readings.
• yaw stabilization using magnetometer/gyroscope readings.
• acceleration stabilization using accelerometer readings.
• configuration through wi-fi.
• altitude hold (kind of, yet tested only within 2.5 meters range)

Devices

• MCU: STM32F303CBT6
• Crystall oscillator: 16 Mhz
• DC-DC converter for control board and camera: TPS5430
• Control board voltage regulator: AMS1117-3.3
• Accelerometer/Gyroscope: MPU6050
• Magnetometer: QMC5883L
• Remote control: ERLS CRSF receiver
• Telemetry/debug: ESP8266 (ESP-07)
• Barometer: HP206C

Project structure

• additional -- the directory containing schematics for the flight controller and BEC:
  • side1.png -- first side of flight controller board that is faced down.
  • side2.png -- second side of flight controller board that is faced up.
  • tps5430.JPG -- DC-DC conveter used to convert battery voltage to 5 volts used by main board's input LDO and FPV camera.
• devices -- drivers for devices used by the flight controller:
  • device.h -- main interface for a character device. Used by almost all devices in devices directory.
  • bmp280.c and bmp280.h -- driver for a bmp280 barometer (currenty unused).
  • crsf.c and crsf.h -- driver for the CRSF protocol used by a ERLS receiver to interract with the main MCU through UART.
  • esp8266.c and esp8266.h -- driver that process AT command used to interact with an esp8266 (esp-07 board to be precise) throught UART.
  • hmc5883l.c and hmc5883l.h -- driver for an HMC5883L magnetometer (currently unused).
  • hp206c.c -- driver for a HP206C barometer.
  • mpu6500.c and mpu6500.h -- I2C driver for mpu6050 and mpu6500 IMUs (accelerometer + gyroscope).
  • qmc5883l.c and qmc5883l.h -- driver for an QMC5883L magnetometer.
• main.c -- all routines related to flight control.
• dsp.c and dsp.h -- functions for PID control and data filtering like low-pass filtering and complimentary filtering.
• uartdebug.c and uartdebug.h -- uartprintf function for debugging.
• all other files are generated by software.
• rc/rc.c -- configuration tool that works through wi-fi connection created by flight controller.

UAV commands

Debug and configuration is performed through AP named copter created by this UAV. Listed commands should be sent using UDP/IP to address 192.168.3.1.

• info (mpu | qmc | hp | values | pid) -- mpu6050/qmc5883L/hp206c/control values/PID data
• r -- turn off motors
• e -- turn on motors
• c [altitude] -- recalibrate
• calib mag (on|off) -- enter/escape magnetometer calibration mode
• pid (tilt|stilt|yaw|syaw|sclimb) (p|i|d) {val} -- set tilt/tilt speed/yaw/yaw speed/climb speed PID P/I/D value
• pid (tilt|yaw) (single/double) -- switch to single/double PID loop mode for tilt/yaw
• compl {val} -- set complimentary filter's time constant for tilt
• lpf (climb|pressure) {val} -- set low-pass filter's time constant for climb speed/pressure
• adj (roll|pitch|yaw) {val} -- set offset for roll/pitch/yaw (only for dual PID loop mode)
• adj mag (x0|y0|z0|xscale|yscale|zscale|decl) {val} -- set x/y/z offset, x/y/z scale or magnetic declination for magnetometer

Quadcopter parameters

• Motors: 1204
• Props: 3016
• Battery: 11.1v (3s), 1100 mAh, 60c
• Frame: plywood

Quadcopter Weight

• PCB and ESCs: ~57g
• Motors + props: 27g
• Battery: 67g
• Frame + wires: ~59g
• Total weight: 220g