Question regarding flash chip alternatives

[piuzera]

Greetings!

I recently ordered a new batch of PCBs and it seems like the flash chip of two of them are having issues. I can flash the software included in the repo and everything works properly but once I unplug and replug, the controller is no longer recognized.

I suspect this is because of a faulty flash chip. Are there any alternatives for the "Winbond Elec W25Q128JVSIQ"? This part is not available in my country and importing it would be very expensive.

Thanks!

[jfedor2]

I don't want to give a recommendation that I didn't test personally, but in general you need a Quad SPI, XIP, 3.3V part (in the same package, obviously). GigaDevice GD25Q128ES* maybe? It doesn't have to be 16 MB. The Pico only has 2 MB.

But based on your symptoms the flash chip seems to work, but maybe not 100% right. Even immediately after you flash it, it's already running from flash, it's just that it doesn't go through the normal bootloader in that scenario. At least that's how I understand it. You might try recompiling the firmware, changing some parameters. Some more info here:

https://forums.raspberrypi.com/viewtopic.php?p=1874492&sid=cdb260577d9bb4485fe8c3cebe2c94fa#p1874492

[piuzera]

Thank you for your help! I'll try out different flashing methods to see if there's any change. Hopefully I don't have to order new parts.

[jfedor2]

Some other folks asked me about the same issue, it seems to be more widespread.

You can try flashing this firmware and see if it helps.

flatbox-rev4-flashtest.zip

[piuzera]

Some other folks asked me about the same issue, it seems to be more widespread.

You can try flashing this firmware and see if it helps.

flatbox-rev4-flashtest.zip

Indeed, this file is working properly, the flatbox is surviving the power cycle. What kind of changes did you make to it? I'd like to test it on GP2040 too, I customized some settings from it and I'd like to fix it too.

[jfedor2]

I will push the changes when I have some time, but I just followed advice from that forum thread and compiled it with the following settings in a board file:

// On some samples, the xosc can take longer to stabilize than is usual
#ifndef PICO_XOSC_STARTUP_DELAY_MULTIPLIER
#define PICO_XOSC_STARTUP_DELAY_MULTIPLIER 64
#endif

// Use slower generic flash access
#define PICO_BOOT_STAGE2_CHOOSE_GENERIC_03H 1

#ifndef PICO_FLASH_SPI_CLKDIV
#define PICO_FLASH_SPI_CLKDIV 4
#endif

#ifndef PICO_FLASH_SIZE_BYTES
#define PICO_FLASH_SIZE_BYTES (2 * 1024 * 1024)
#endif

// All boards have B1 RP2040
#ifndef PICO_RP2040_B0_SUPPORTED
#define PICO_RP2040_B0_SUPPORTED 0
#endif

(It's likely one of the first three, or a combination of them.)

[jfedor2]

After some more testing by other users I now think it's the crystal oscillator part that's problematic, not the flash chip. The latest firmware has a workaround for that (PICO_XOSC_STARTUP_DELAY_MULTIPLIER 64, as mentioned above).

[piuzera]

Thanks! It now works flawlessly. I'll be closing the issue.