I have an Arduino Uno connected to a motor controller over I2C. The Arduino accepts commands from a Raspberry Pi via the USB serial line.
I'm trying to diagnose a problem where the Arduino will become completely unresponsive. It's programmed to respond to a "ping" request every N seconds, and for some reason I can't identify, it seems to crash and no longer respond to any commands. However, the motor controller continues powering the motors.
Everything is powered from a 12V Li-Po battery, but everything is located behind 5V regulators. When this problem happens, the battery is fully charged and the motors aren't sourcing much current, and neither the motor controller or Raspberry Pi are effected, so I've ruled out a brownout.
My theory is there's some subtle programming error in my Arduino code that's causing an "exception", but I don't know how to identify it. I've tried adding special code to allow me to trigger one of these, by indexing an array outside of its limits or calling a null function pointer, but the Arduino stubbornly refuses to crash when I try to explicitly make it.
How do I diagnose an Arduino becoming unresponsive?