Interesting SPI Routing with iCE40 FPGAs

https://danielmangum.com/posts/spi-routing-ice40-fpga/

by hasheddan • 9 months ago

99 10 9 months ago

Graziano_M3• 8 months ago

I enjoyed playing with FPGAs and all the open-source tooling makes it so much quicker and easier.

That said, I never understood the appeal of the FOMU. It's cool that it fits in a USB port, but so little IO, there's not a lot I can think to do with it.

Has anyone heard of some cool projects that others have done with this hardware?

CamperBob2• 8 months ago

I suppose you could create your own crypto wallet or something, but agreed, an FPGA without I/O is not a very interesting or useful thing. You'd be better off with a conventional microcontroller, I'd think.

duskwuff• 8 months ago

You'd be better off with a conventional microcontroller, I'd think.

Or with a more conventional FPGA development board like Icebreaker:

https://1bitsquared.com/products/icebreaker

Aurornis• 8 months ago

The primary appeal of these minimalist devices is to get people started as cheaply as possible.

They exist at a price point where it’s an easy decision to pick one up on a whim and spend an evening installing the toolchain and building some little hello world tutorial.

Graziano_M3• 8 months ago

I was typing out a response saying that you can buy an ice stick for cheaper, I went to check the price and it's $150 now! https://www.digikey.com/en/products/detail/lattice-semicondu...

I bought one for $25 back in 2018! What's going on here?

That obviously makes the FOMU a more reasonable starter purchase, but I'd still probably get an icebreacker for $80 (which I also have and love).

sylefeb• 8 months ago

Hi there, a while ago I had a ton of fun with the Fomu: https://x.com/sylefeb/status/1571489610647371776

Fantastic little device! Relating to the post, I also happened to brick one erasing the Foboot bootloader by writing the flash beyond the limit (there was a bug regarding writing to addresses beyond max at the time, but then I was pushing the limit by abusing dfu-utils :) https://x.com/sylefeb/status/1391898565061001225 ). I tried to use the programming pads but at the time was lacking the skills and it ended in disaster (ripped pads...).

The code repo for the overall project is here: https://github.com/sylefeb/tinygpus

Graziano_M3• 8 months ago

Wow very cool.

ChrisGammell• 8 months ago

I aggressively enjoyed this post

cushychicken• 8 months ago

Oh my god I fucking HATE the SPI config bus on the ice40 series

So difficult to get the directionality right and also enable a JTAG bus

Hate these parts for that reason

imtringued• 8 months ago

I was thinking about an "In-system programming" use case and thought about how to best do it and the biggest problem by far is that powering the flash chip also powers the rest of the system. What a pretty niche topic to have a Baader–Meinhof phenomenon happen to you.

I have to agree with others that the "Fomu" design appears to be highly suboptimal. They could have given you a way better edge connector on the other side.

Interesting SPI Routing with iCE40 FPGAs

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