AVR-Chat

This is a part of the art that isn't taught much..

How to diagnose or debug a problem.

Basically, you need to divide up your system, to know that "THIS PART
WORKS", and keep sectioning off the problem into a smaller and smaller
space until you have it cornered.

I learned this art in analog electronics, how to divide up the system
and isolate the problem. The approach works just as well with
software, and with microcontrollers it's not all that unusual to have
problems that are both in hardware and in software.

"drive a stake in the gound" with some part of your code that outputs
something you can see, and be absolutely sure that it always works.
Use that to debug other parts of the system.