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.
• dshot-300 ESC control protocol.
• IRC Tramp VTX control.
• telemetry through eLRS.
• terminal configuration tool.
• Qt5 based GUI configuration tool for desktop and android.

• MCU: STM32F405RGT6
• Crystall oscillator: 20 Mhz
• DC-DC converter for control board and camera: TPS5430
• Control board voltage regulator: AMS1117-3.3
• Accelerometer/Gyroscope: ICM-42688-P
• Magnetometer: QMC5883L
• Remote control: ERLS CRSF receiver
• Telemetry/debug/config: ESP8285
• Barometer: DPS368

• pcb -- the directory containing schematics for the flight controller and BEC:

  • bottom.png -- bottom side of flight controller board.
  • top.png -- top side of flight controller board.
  • ground.png -- ground layer of flight controller board.
  • power.png -- power layer of flight controller board.
  • tps5430.JPG -- DC-DC conveter used to convert battery voltage to 5 volts used by main board's input LDO and FPV camera.
  • conponentvalues.txt -- values and types for components on schematics.

• additional -- additional files

  • frame.dxf -- quadcopter frame outline.

• 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.
  • uartconf.c and `uartconf.h -- driver that receives and sends data through one of UART's used for configuration and debugging.
  • 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 used to exchange data with esp8285 through SPI.
  • hmc5883l.c and hmc5883l.h -- driver for an HMC5883L magnetometer (currently unused).
  • hp206c.c and hp206c.h -- driver for a HP206C barometer.
  • dps368.c and dps368.h -- driver for a DPS368 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.
  • icm42688.c and icm42688.h -- driver for an icm42688 IMU (accelerometer + gyroscope).
  • m10.c and m10.h -- driver for a M10 GNSS module.
  • w25.c and w25.h -- driver for a w25q SPI flash.
  • irc.c and irc.h -- driver for an IRC Tramp controlled VTX device.

• main.c -- all routines related to flight control.

• global.h -- global values used in many places in source code.

• crc.h -- CRC-8 implementation.

• stm32periph.c and stm32periph.h -- stm32 periphery initialization and error handling.

• util.c and util.h -- common utility functions that can be used in more than one source file.

• dsp.c and dsp.h -- functions for PID control and data filtering like low-pass filtering and complimentary filtering.

• command.c and command.h -- configuration and informational commands processing API.

• timev.c and timev.h -- periodic event processing API.

• uavconf/uavconf.c -- configuration tool that works through wi-fi AP created by flight controller using UDP protocol.

• uavconf_gui -- gui configuration tool:

  • main.cpp -- entry point for GUI configuration tool.
  • mainwidget.cpp -- implementation for Qt5 related functions.
  • mainwidget.h -- headers for Qt5 related functions.
  • uavconf.c and uavconf.h -- API for UDP interaction with UAV.

• uavconf_droid -- project for andriod gui compilation.

• all other .c, *.h and *.s files are generated by software.

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.

• r -- turn off motors
• c [altitude] -- recalibrate and set altitude reference value.
• calib mag (on|off) -- enter/escape magnetometer calibration mode
• flash (write|read) {N} -- write/read settings into/from MCU's internal flash slot '{N}'.
• system esp (flash|run) -- set onboard wi-fi chip to flash/run mode.
• info (mpu | qmc | hp | | dev | values | pid | gnss | ctrl | filter) -- get various values and infomation:
  • mpu -- ICM-42688-P IMU data.
  • qmc -- QMC5883L magnetometer data.
  • dev -- all devices status.
  • values -- configuration values.
  • pid -- PID values.
  • gnss -- M10 GNSS data.
  • ctrl -- eLRS remote configuration values.
  • filter -- complimentary and LPF filters configuration values.
• log set {l} -- set log length to {l} records and if {l} greater than 0 start logging. If {l} is 0, stop logging.
• log rget {b} {e} -- get log records whose number starts from {b} and end with {e} - 1.
• log bget {n1}...{nN} -- get batch of log records with numbers {n1}...{nN}.
• log freq {val} -- set log frequency.
• log record size {val} -- set log record size.
• log {N} {name} -- set '{N}'-th log field to value named '{name}'.
• pid (tilt|yaw) mode (single/double) -- switch to single/double PID loop mode for tilt/yaw.
• pid (tilt|stilt|yaw|syaw|throttle/climbrate/altitude) (p|i|d) {val} -- set PID controller values:
  • tilt -- tilt PID controler P/I/D value.
  • stilt -- pitch/roll rotation speed PID controller P/I/D value.
  • yaw -- yaw PID controller P/I/D value.
  • syaw -- yaw rotation speed PID controller P/I/D value.
  • throttle -- acceleration PID controller P/I/D value.
  • climbrate -- climb speed PID controller P/I/D value.
  • altitude -- altitude PID controller P/I/D value.
• compl (attitude/yaw/climbrate/altitude) {val} -- set complimentary filters time constants:
  • attitude -- filter that mixing accelerometer and gyroscope data to get pitch/roll value.
  • yaw -- filter that mixing gyroscope and magnetometer data to get yaw value.
  • climb rate -- filter that mixing acceleromter interated data and barometer data to get climb speed value.
  • altitude -- filter that mixing climb rate value and barometer data to get altitude value.
• lpf (gyro/accel/d/climb) {val} -- set low-pass filter's time constant for gyroscope/accelerometer/d/vertical acceleration.
• adj (rollthrust/pitchthrust) {val} -- adjust motors thrust.
• adj (roll|pitch|yaw) {val} -- set offset for roll/pitch/yaw (only for dual PID loop mode).
• adj acc (x|y|z) {val} -- set x/y/z offset for acceleromter
• adj gyro (x|y|z) {val} -- set x/y/z offset for gyroscope
• adj mag (x0|y0|z0|xscale|yscale|zscale|decl) {val} -- set x/y/z offset, x/y/z scale or magnetic declination for magnetometer
• adj curr (offset|scale) {val} -- set current meter offset/scale value.
• adj althold hover {val} -- set hover throttle.
• ctrl (roll|pitch) {val} -- set maximum roll/pitch tilt value in radians.
• ctrl (sroll|spitch) {val} -- set roll/pitch rotation speed in for single loop mode in radians.
• ctrl (syaw|yaw) {val} -- set yaw rotation speed for single/double loop mode in radians.
• ctrl accel {val} -- set maximum acceleration for throttle loop.
• ctrl climbrate {val} -- set maximum climb rate in m/s.
• ctrl altmax {val} -- set maximum altitude in meters.

Log records got by commands log rget and log bget are just lines with set of space separated numeric strings and have such format:

 {CRC} {number} {v0} ... {vN} 

, where {CRC} is CRC-8 sum of record line, {number} -- record number and {v0} ... {vN} -- N record values.

• Motors: 1404, 3800 kV
• Props: 3030
• Battery: 14.8v (4s), 1300 mAh, 120c
• Frame: carbon fiber

• PCB and camera: 20g
• ESC: 30g
• Motors + props: 48g
• Battery: 148g
• BEC: ~6g
• Antenna: 10g
• Frame: ~114g
• Total weight: 376g