New Firmware

To install new firmware (MicroPython, CircuitPython, or your own UF2), you simply overwrite the existing flash.

Put the Pico into BOOTSEL mode

Disconnect the Pico. Hold the BOOTSEL button. Plug it into your computer while still holding BOOTSEL. Release the button.

It will appear as a USB mass storage device called:

RPI-RP2

Install new firmware

Just drag and drop the new .uf2 file onto the RPI-RP2 drive.

The Pico will automatically:

erase the existing firmware (including MicroPython), write the new firmware, reboot.

Completely erase

If you want to completely blank the flash first

The Raspberry Pi Foundation provides a special UF2 that erases the entire flash.

Download flash_nuke.uf2. flash_nuke.uf2 https://datasheets.raspberrypi.com/soft/flash_nuke.uf2?utm_source=chatgpt.com Copy it to RPI-RP2. The Pico will reboot with a completely blank flash. Put it back into BOOTSEL mode and install the firmware you want.

This is occasionally useful if:

the filesystem has become corrupted, MicroPython won't boot, you're repurposing the Pico.

The official Raspberry Pi flash_nuke.uf2 is available directly from Raspberry Pi.

To use the clean flash

Hold BOOTSEL while plugging the Pico into USB.

It appears as RPI-RP2.

Copy flash_nuke.uf2 onto the drive.

The Pico will reboot after erasing its flash.

Put it back into BOOTSEL mode and copy on the MicroPython UF2 (or whatever firmware you want).

For your five boards, I'd probably skip flash_nuke unless they're behaving strangely. In most cases, simply copying a new MicroPython UF2 over the top completely replaces the existing firmware. flash_nuke is mainly useful if:

the filesystem is corrupted, the Pico won't boot, or you want to guarantee the flash is completely erased before reusing the board.