Jin Quadcopter Flight Control

Personal development for quadcopter flight control firmware

FC H/W

1. MCU: STM32F405R
2. Main 9 DOF Sensor IC: BNO080/085 - control 3 axis angle position
3. Sub 6 DOF Sensor IC: ICM-20602 - control 3 angular acceleration
4. Barometer: LPS22HH - hovering later
5. EEPROM: AT24C08 - memory for PID gain
6. LED and Buzzer for debugging
7. GPS/GNSS: UBlox M8N (Communication protocol - UBX (Not NMEA)
8. Trasmitter and Receiver: FS-i6, FS-iA6B based on i-BUS protocol
9. Electronic Speed Controller (ESC): Favourite LITTLEBEE 30A - S

S/W

1. Tool: STM32CubeIDE
2. Language: C
3. Main libraries
   • BNO080
   • ICM20602
   • M8N UBX Parsing
4. ESC Firmware
   • Protocol: OneShot125 - PWM signals, Duty Cycle: 125us ~ 250us (8kHz ~ 4kHz)
   • Firmware: BLHeli_S
   • 10500 Steps in Duty Cycle
   • ESC Control Factors in STM32F4
     • Use TIM5 in STM32F4, CH1, CH2, CH3, and CH4 Generating by TIM5
     • TCLK: 84MHz
     • ARR(Auto Reload Register): 42000, Set as 41999 in STM32CubeIDE
     • PSC(Prescaler): 1, Set as 0 in STM32CubeIDE
     • CK_CNT = 84MHz / 1 = 84MHz
     • CCR(Capture/Compare Register): 10500 ~ 21000 -> Total Steps : 10500
     • Count Moder: Up Count

Peripheral

CALIBRATION

1. BNO080 - 9 DOF Sensor

   • BNO080's MEMS sensor should be calibrated for best performance
   • Hilcrest Lab's "Dynamic Calibration Algorithms": It can calibrate the sensor simply by moving the device in specifice motions
   • The calibration results are saved in flash on the BNO080 in a file known as the Dynamic Calibration Data (DCD) file
   • Ideally the calibration process would be performed several feet away from high magnetic intefers like tables with magnetic components, desktop PC towes, monitors, etc.
   • Configuration
     • Enable dynamic calibration for accelerometer, gyroscrope, and magnetometer
     • Enable Game Rotation Vector output
     • Enable Magnetic Field output
   • Calibration Procedure: Accelerometer -> Gyroscrope -> Magnetometer
     • Position the device in a relatively clean magnetic environment
     • Begin observing the Status bit of the Magnetic Field output
     • Perform the accelerometer calibration motions. The accelerometer will be calibrated after the device is moved into 4-6 unique orientations and held in each orientation for ~1 second. One way to think about this is the "cube" method.
       • Orient the device so that it is sitting on each face of the cube sequentially
       • Hold the device in each position for 1 second
         • If one of the faces is difficult to position the device, you do not need to do all 6 faces.
         • The position do not need to be perfectly aligned with the cube faces
         • It does not matter which order the cube face positions are moved into
     • Perform the gyroscope calibration
       • Set the device down on a stationary surface for ~2-3 seconds to calibrate the gyroscope
     • Perform the magnetometer calibration
       • Rotate the device ~180degree and back to the beginning position in each axis(roll, pitch, yaw)
       • The speed of the rotation should be ~2 seconds per axis
       • Observe the Status bit of the magnetic field output
       • Continue rotations until the Magnetic Field Status bit reads 2 or 3 (medium or high)
     • When finished with the calibration methods, run the Save DCD Now command, which will save this calibration data into flash

2. ICM20602 - 6 DOF Sensor

   • Estimates the gyroscope offset values of X, Y, and Z
   • Multiply the offset values by -2
   • Write the values to each registers like below

     ICM20602_Writebyte(0x13, (gyro_x_offset * -2) >> 8);
     ICM20602_Writebyte(0x14, (gyro_x_offset * -2));
     ICM20602_Writebyte(0x15, (gyro_y_offset * -2) >> 8);
     ICM20602_Writebyte(0x16, (gyro_y_offset * -2));
     ICM20602_Writebyte(0x17, (gyro_z_offset * -2) >> 8);
     ICM20602_Writebyte(0x18, (gyro_z_offset * -2));
     

   • Big Endian
   • Should write every boot-up process