The FPGA normally boots from a dedicated serial NOR flash. This flash can be programmed by the Pico processor which exposes the flash to the host OS as either a removable drive or a DFU endpoint.

On Windows, while the RaspberryPi guide mentions using Visual Studio Code with a plugin a an IDE, better results were obtained by using the WSL2 environment.

With Micropython

Out of the box, pico2-ice comes with a micropython firmware loaded in the RP2350, you can use it to upload bitstreams to the FPGA:

1. Copy bitstream file to the USB MSC disk provided by micropython, unplug and replug the pico2-ice. Alternatively, use mpremote to copy the file mpremote cp file.bin :
2. See the usage of micropython to upload your bitstream to FPGA flash or FPGA RAM: How to use Micropython

Troubleshooting

Checking the CDONE pin

Once the FPGA bitfile transfers over using the DFU protocol, the Pico will check for whether the DONE pin goes high indicating a successful boot. This would make the CDONE green LED bright. If this doesnt happen for whatever reason, the DFU utility will throw an error indicating that this did not succeed.

Booting the FPGA with custom firmware

The user writing a custom firmware with the pico-ice-sdk should take care of starting the FPGA from the MCU. Review the rp2_fpga example for how this can be done.