I can't flash circuitpython via USB-C port.

[Ne0joke]

I have built the entire hardware on my own. I didn't bought the i2c flash devices, so I only add the USB type-c port. When I plug it in my computer, I can get a USB storage device called "RPI-RP2". It totally works, I can copy anyother files in it, but when I copy the circuitpython's ".uf2" file into it. It reboots and nothing happened but the .uf2 file disappeared. I build another board and tried the same thing, and same thing happened again.
So, I don't know what to do now. Although I'm pretty good at soldering pcb boards, I'm a entire freshman on the software area. Is there any necessary software I didn't install or anyother probably reasons that caused my problem to happen? Or I need to flash it via the i2c port?
Need your help...thanks.
;)

[arturo182]

Hmm, that's really weird. The only ways to flash it are USB and SWD, there is no I2C flashing. If you copy over the .uf2 and the chip still reboots into bootloader mode, I'd suspect it's something with the flash chip, if the RP2040 doesn't find valid firmware on the flash chip, it will stay in bootloader mode. Are you using the exact same flash chip as in the BOM?

[Ne0joke]

Uh...Acutally I can't find the same chip in the BOM at my local shop (the model GD25Q16xS), I can only find a model GD25Q16CSIG. According to the chip's manual it is a 16M flash chip, but when I plug it in my computer I got a 127MB USB flash drive and it actually works I can copy files over 100MB into it. But according to RP2040's manual it can support 16M at most, so I guess it is because I got the wrong flash chip on it. I will try to use another model of flash chip instead. Thank you for your help, lol.

[Ne0joke]

Emmmm...I check the image of the board on the solderparty website again, I think we are using the same flash chip (at least the latters are the same). It's really strange. Do I need to connect the BBQ20 keyboard to the board before I try to flash it with circuitpython?

[arturo182]

The size of the uf2 drive doesn't matter, it's SW-defined and large enough to work with my FLASH. uf2 files are usually 2x the size of the FLASH so the drive has to be at least 32MB to support 16MB FLASHes, they made it 127MB to not have to worry about that. The keyboard doesn't need to be connected for the flashing or booting of the RP2040 to work. Hard to tell what's wrong, tbh. If it stays in bootloader mode then I would still suspect something related to FLASH since it will stay in bootloader if it can't properly read and execute code from the FLASH chip.