Hi Josverl,

I will try, but I am not sure what specifics you mean. Please ask if I miss something.

I use an IS25LP128F flash chip (capacity: 16 MB, QuadSPI, 166 MHz max speed according to the datasheet).

All other changes compared to the Pico2 should not be an issue, because I can run the pico-examples fine, the device shows up as mass storage, etc.

So the issue is:

All builds finish fine with no compile errors, but I cannot see any action. I set up a toggling pin in ports/rp2/main.c directly at the start of main, but I see nothing on the scope. This did work on an original Pico2, though.

I suspect that the flash configuration is faulty, but why does it work with an example from the Pico SDK? As far as i can see, the board file of the RPI_PICO2 is directly linked to lib/pico-sdk/src/boards/include/boards/pico2.h. I also ensured that the examples are using the same SDK.

So I am out of ideas, especially because the same example UF2 files (hello_world_usb, blink, etc.) are working for both designs, but the MicroPython build only works for the Pico2.

Best regards and thank you very much!

As it looks like your code is not reaching the start of main() in ports/rp2/main.c, the board is could be hanging or hard-faulting during the second-stage bootloader (boot2) phase or the early runtime initialization before main() is called.

The RP2 series requires boot2 to configure the external flash chip for Execute-in-Place (XIP) via QSPI. If the commands sent by boot2 to switch the flash into continuous read/Quad-SPI mode aren't supported by the IS25LP128F exactly as the bootloader expects, the CPU will crash the moment it tries to fetch the first instruction of the actual MicroPython firmware.

While MicroPython uses the Pico SDK under the hood, the MicroPython build system explicitly overrides several SDK defaults in its board configuration files (e.g., mpconfigboard.cmake and mpconfigboard.h). The standard RPI_PICO2 MicroPython target is optimized for the flash chips on the official Pico 2 (usually a Winbond or Macronix chip) and might trying to use flash parameters that your IS25LP128F chip rejects.

I think you may be able to configure this in your board's mpconfigboard.cmake

set(PICO_BOOT_STAGE2_CHOOSE_GENERIC_03H 1)
or 
set(PICO_BOOT_STAGE2_CHOOSE_ISSI 1)

Hi, thank you very much for your approach!

I like this comment in boot2_generic_03h.S very much:
// * This enables you to boot from almost anything: you can pretty
// much solder a potato to your PCB, or a piece of cheese

:-)

But unfortunately, it does not work.

To make sure that my build pipeline did what you said, I used preprocessor debugging via #warning to be 100% sure that the correct boot2 config was being used:

micropython/lib/pico-sdk/src/rp2350/boot_stage2/boot2_generic_03h.S:122:2: warning: #warning "Using the Potato Flash!" [-Wcpp]


  122 | #warning "Using the Potato Flash!"
      |  ^~~~~~~

Nothing works; it is still the same issue.