Snowflake-FPGA

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The Fomu EVT boards where RPi based hats too. Thus @xobs wrote a great little tool for bitbanging SPI to program the iCE40 and SPI on the board (even supports things like QPI mode!).

Take a look at https://github.com/im-tomu/fomu-flash - more than happy to add your board as a target option.

(There is also a tool which builds a RPi image with all the ice40 tooling at https://github.com/im-tomu/fomu-pi-gen too.)

I rather wanted the fun of doing this myself! :cry: Thank you for the link to the tools, they look handy. If I end up modifying these then I will submit a PR.

Is there an advantage of the Fomu ROM patching vs icebram?

The advantage to the Fomu ROM patching vs icebram is that it's less to keep track of, and ends up being faster:

• icebram requires an input ROM, an output ROM, an input hexfile, and an input binary. Foboot just requires an input ROM and an input binary.
• The icebram hexfile needs to be in a specific order, and I ended up needing to come up with additional tools to massage the bitstream into the correct format. fomu-flash works on binary images.
• fomu-flash is near-instant, whereas icebram took several seconds

In the end, both accomplish the same thing, so if you're already using icebram then there's no need to change.