Get free stack size on Raspberry Pi Pico2 (RP2350)

vasya-serega · December 6, 2025, 2:12pm

Hi,

who can have any ideas how to get free stack size on Raspberry Pi Pico2 (RP2350)?

On RP2040 we can call rp2040.getFreeStack() and get proper value. On RP2350 the method returns 270272 and it does not seem to be true.

Platform.ini is:

[env:5500_evb_pico2]
platform = https://github.com/maxgerhardt/platform-raspberrypi.git
board = wiznet_5500_evb_pico2
board_build.core = earlephilhower
board_build.filesystem_size = 0.5m
framework = arduino
test_framework = unity
test_build_src = yes
build_flags = 
	'-D SHIELD="W5500-EVB-Pico2"'
build_unflags = -fno-rtti

maxgerhardt · December 6, 2025, 2:24pm

Then plesse open an issue in https://github.com/earlephilhower/arduino-pico/issues, not here.

The getFreeStack() function assumes 0x20040000 is the end of memory.

github.com/earlephilhower/arduino-pico

cores/rp2040/RP2040Support.h

5c9443031


      
          /**
              @brief Calculates approximately how much stack space is still available for the running core.  Handles multiprocessing and separate stacks.
          
              @details
              Not valid in FreeRTOS.  Use the FreeRTOS internal functions to access this information.
          
              @returns Approximation of the amount of stack available for use on the specific core
          */
          inline int getFreeStack() {
              const unsigned int sp = getStackPointer();
              uint32_t ref = 0x20040000;
              if (setup1 || loop1) {
                  if (core1_separate_stack) {
                      ref = cpuid() ? (unsigned int)core1_separate_stack_address : 0x20040000;
                  } else {
                      ref = cpuid() ? 0x20040000 : 0x20041000;
                  }
              }
              return sp - ref;
          }

And assumes RAM is 256 kB plus 2*4 KB scratch memory in

github.com/earlephilhower/arduino-pico

ota/memmap_ota_rp2350.ld

5c9443031


      
          RAM(rwx) : ORIGIN =  0x20000000, LENGTH = 212k
          GLOBALS(rwx) :   ORIGIN = 0x20035000, LENGTH = 44k
          SCRATCH_X(rwx) : ORIGIN = 0x20080000, LENGTH = 4k
          SCRATCH_Y(rwx) : ORIGIN = 0x20081000, LENGTH = 4k

vasya-serega · December 6, 2025, 2:32pm

@maxgerhardt ok, the issue was created there.

maxgerhardt · December 6, 2025, 9:30pm

Fixed in Fix rp2040.getFreeStack() on RP2350 by earlephilhower · Pull Request #3255 · earlephilhower/arduino-pico · GitHub and synced with PlatformIO in Sync boards, include Arduino-Pico hotfix · maxgerhardt/platform-raspberrypi@49292d1 · GitHub.

A regular pio pkg update -g -p raspberrypi on the CLI should update the platform and include that fix.

vasya-serega · December 7, 2025, 6:23am

Thanks for quick fix!

pio pkg update -g -p raspberrypi didn’t help, so I had to clean up and get again .platformio folder

maxgerhardt · December 7, 2025, 12:35pm

Weird. Then

pio pkg update -g -p https://github.com/maxgerhardt/platform-raspberrypi.git

might do it next time.

electricidea · January 7, 2026, 7:53pm

Worked for me for the Olimex Pico2XXL board. Thanks!