Mahmood has listed the basic things everyone needs to do when working on microcontrollers. We all get to the point sometime when it "doesn't work." Our familiarity with our own work often makes it all the more difficult to see the problems in it. Sometimes you have to ask for help.

I would add to Mahmood's list when asking for such help:

1. What *exactly* doesn't work?
2. What is the code *supposed* to do?
3. What have you done to try to make it work?
4. What debug tools do you have available to you? (emulator, scope, simulator, logic probe, LED, etc.)
5. Show your code, and any errors and warnings your compiler and/or assembler might have given you.

Answers to these questions at the start will prevent needless guessing and wasted time speculating on what the real problem might be, and allow more useful suggestions to be made.

Dennis