Cornell University ECE4760
Debugging
Pi Pico RP2040/2350

Datasheet Errata

Build Bugs

1. Cmake configuration.
   Cmake can go wrong in a number of ways while configuring the project, with very limited error messages in the VSCode window.
   You can invoke cmake at the powershell command line by changing directory to your current build directory then issuing the command: 
   cmake "NMake Makefiles" ..
   (note the quotation marks and two periods at the end; both are part of the command)
   An example shows that on my system, the absolute path to cmake was necessary. It also shows
   that you can read out which board and cpu the systems thinks you want, and will issue error messages
   that make sense if soemthing goes wrong.

Protothread Bugs

If your program just sits there and does nothing:
-- Did you write each thread to include at least one YIELD (or YIELD_UNTIL, or YIELD_TIME_msec) in the while(1) loop? Remember that the UART input spawned
thread yields betwen eacy typed character. Humans are sooo slow.
-- Did you schedule the threads?
-- Does the board have correct Vdd?

If your program reboots about a few times/sec:
-- Did you exit from any scheduled thread? This blows out the stack.
-- Did you turn on any interrupt source and fail to write an ISR for that source?
-- Did you divide by zero? A divide by zero is an untrapped exception.
-- Did you write to a non-existant memory location, perhaps by using a negative (or very large) array index.
A write to a non-existant memory location is an untrapped exception.

If your thread state variables seem to change on their own:
--- Did you define any automatic local variable?
Local variables in a thread should be static.
-- Are your global arrays big enough the clobber the stack in high memory?
You should be able to use over 400 kbytes.

Runtime Exceptions

1. You can find out more about openOCD here.

Copyright Cornell University April 28, 2025