Question

I have a watchdog in my microcontroller that if it is not kicked, will reset the processor. My applications runs fine for a while but will eventually reset because the watchdog did not get kicked. If I step through the program it works fine.

What are some ways to debug this?

EDIT: Conclusion: The way I found my bug was the watchdog breadcrumbs.

I am using a PIC that has a high and low ISR vector. The High vector was suppose to handle the LED matrix and the Low vector was to handle the timer tick. But I put both ISR handlers in the high vector. So when I disabled the LED matrix ISR and the timer tick ISR needed service, the processor would be stuck in the low ISR to handle the timer tick, but the timer tick handler was not there.

The breadcrumbs limited my search down to the function that handled the led matrix and specifically disabling the LED matrix interrupt.

Answer 1

Add an uninitialized global variable that is set to different values throughout the code. Specifically, set it before and after major function calls.

Put a breakpoint at the beginning of main.

When the processor resets the global variable will still have the last value it was set to. Keep adding these ‘bread crumbs’ to narrow down to the problem function.