Compass
I managed to get the compass attached to the i2c bus without causing the AVR to hang, but I couldn't read the compass without the RS-485 protocol timing out. I attached the compass via the PWM signal, but have not been able to get satisfactory results. The theoretical resolution of the compass as it is currently configured is 2.7 degrees. This change also seems to have broken the motor controller status notification on boot; the motor controller still works fine. I haven't checked in any of the new code, because it still works less well than what's in the repository.