4 ms·

Interesting SPI Routing with iCE40 FPGAs

99 points by hasheddan 11mo ago

Graziano_M 11mo 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 11mo 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 11mo 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 https://1bitsquared.com/products/icebreaker
- Aurornis 11mo 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_M 11mo 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-semiconductor-corporation/ICE40HX1K-STICK-EVN/4289604 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 11mo ago
  Hi there, a while ago I had a ton of fun with the Fomu: https://x.com/sylefeb/status/1571489610647371776 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 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 https://github.com/sylefeb/tinygpus
  - Graziano_M 11mo ago
    Wow very cool.
ChrisGammell 11mo ago
I aggressively enjoyed this post
cushychicken 11mo 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 11mo 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.

99 points by hasheddan 11mo 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 11mo 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 11mo 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 https://1bitsquared.com/products/icebreaker
Aurornis 11mo 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_M 11mo 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-semiconductor-corporation/ICE40HX1K-STICK-EVN/4289604 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 11mo ago
Hi there, a while ago I had a ton of fun with the Fomu: https://x.com/sylefeb/status/1571489610647371776 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 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 https://github.com/sylefeb/tinygpus
- Graziano_M 11mo ago
  Wow very cool.

ChrisGammell 11mo ago

I aggressively enjoyed this post

cushychicken 11mo 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 11mo 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.