[jaustin]

Yes you are both (Pat & Mark) correct relative to the speed differences of the EDU motors in fwd & rev. I have been able to slow the one side down in the code to allow it to track fairly straight. I just added a 60/100 factor at the end of the PID routine to the right sides pwm value and it works ok now.

Mark,
On the other problem I too suspect some kind of memory over-write or over-flow problem. I printed out the rc values and they show up as either 1 or 0 99.9% of the time. But occasionally a random 485 or 2046 shows up and then things go south. I'm kind of a novice with the PIC and C. I not familiar with how to create a .map file to check my memory allocations. Is there a website that explains how to do it? Should I use the "extern int" identifier for rc to ensure it's a global variable somewhere outside the robot_command() function? (if that's it, I'm curious why Kevin did not do it that way to start with).

Thanks guys for all your help!

Jeff