OHMC2020 Troubleshooting guide
Check the I2C components are working
$ i2cdetect -y 1
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- 3c -- -- --
40: 40 -- -- -- -- -- -- -- -- -- -- -- -- 4d -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- 68 -- -- -- -- -- -- --
70: 70 -- -- -- -- -- 76 --
GY-91 10DOF MPU-9250 & BMP280
0x3C - OLED Display (SSD1306_128_64)
0x40 - PCA9685PW: Normal use (PWM / servo)
0x4D - MPC3021 (battery volt ADC) 1001101X
0x68* - MPU9250 (gyroscope/accelerometer sensors)
0x70 - PCA9685PW: All call address (PWM / servo)
0x70 - PCA9685PW (PWM / servo)
0x76* - BMP280 (pressure)
If the output doesn't look like this, something isn't being detected properly and your car may not be working as expected.
rPi reboots and Auto-starting donkeycar without logging in
If your rPi reboots when you're driving, check the following things:
- did you swap the servo wires between steering and power. Turn the ESC off, unplug one servo wire, turn the ESC back on (little toggle switch), and test steering. Make sure that steering does not activate the wheel motors.
- is your battery low? are you accelerating too quickly?
Because the battery has a high internal resistance, if you demand a lot of power too quickly, the voltage on the battery drops enough that the rPi gets below its critical voltage (when you add the voltage drop from the voltage converter), and the rPi reboots.
To restart donkey server automatically, do the following on your car:
- Add this to /etc/rc.local:
su - pi -c 'cd ~/ohmc_car; python manage.py drive &>/tmp/out' &
- move 'source ~/env/bin/activate' from ~/.bashrc to ~/.profile
Steering and throttle calibration
To save time at the workshop, you won't need to calibrate your car's steering and/or throttle. However, you may get better results and can perform calibration when you have time.
