[avr-chat] mega644 will not run except single-step revisited
From:
Steve Franks
Subject:
[avr-chat] mega644 will not run except single-step revisited
Date:
Fri, 1 Sep 2006 07:47:20 -0700
So, again, I post my ever inexplicable debugging circus publicly.
A while back, I mentioned a Mega644 that was doing strange things. Then someone lost completely all our prototype boards. Now new boards are back, and the problem is back with them.
The only thing I can say with certainty:
1) If one programs the board, or brings up the debugger in Avrstudio and hits 'run', no code ever appears to execute, and the 'lost communication' light on the jtagiceII starts flashing.
2) If one instead single-steps, the program executes fine, right down to puts functions and everything. If you hit F5 at any point in the program, no more execution is apparent and the lost comm light starts flashing again.
Some details:
We're on a 4-layer board with ground & power planes. Solder job appears impeccable under the inspection microscope. Running off 8MHz internal clock. 1MHz and 128kHz internal clocks behave identically. Frequency at clock out pin looks very stable. Mega644 is in QFN/MLP package. Mega644 is cool to touch. Putting hard connection from reset pin to power (and ground, obviously) has no effect. Behavior is apparent at all optimization levels. Compiler is WinAvr200604... AvrStudio is 412sp3. When I say 'no code is executed', I mean that there is no Uart output, and LED changes were inserted every couple of lines throughout the code which do not occur. LED's and uart output always work as expected when single-stepping.