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  • clifflecliffle@hachyderm.io
    Oct 14, 2026, 6:06 PM

    So there's this thing I've been wanting, and can't find for purchase, so I guess I've gotta make it.

    The Pi Pico has become a de-facto standard for "microcontroller you plug into something." But what if you want to make the CPU yourself?

    There are plenty of boards that have an RP2xxx chip _and_ an FPGA, but they generally have a different pinout. I haven't been able to find one that's _just_ an FPGA and has the right pinout.

    So, here's 5k LUTs, 128 kiB of SRAM, and several meg of flash. I'm hoping to put this in my PicoCalc so that it runs my CPUs natively.

    A PCB design shown in multi-colored CAD view, with a single chip in the center and a bunch of pin headers in roughly the shape of a DIP40
    A 3D render of a PCB about the size of a Pi Pico or, if you're my age, a BASIC Stamp
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Replies

  • clifflecliffle@hachyderm.io
    Oct 14, 2026, 6:09 PM

    Also, kicad on a 10" display is Not Great but workable.

    A photo of my cafe CAD setup with my mini laptop on a stand over my keyboard
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  • clifflecliffle@hachyderm.io
    Oct 14, 2026, 6:12 PM

    @omixann I'm designing around the ICE40UP5K, which is unusual for having (relatively) large SRAMs in-package. It's also available in a compact QFN package, and is too small to be useful for "AI" so its price hasn't gone totally nuts.

    But it's quite slow -- I don't expect to get timing closure at better than 20 MHz for my SoC. I'm considering swapping in an ICE40HX8K in BGA, but it'll be harder to make at home, and it'd need an external SRAM (and small SRAMs are weirdly expensive right now).

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  • rude Goldberg machinedngrs@chaos.social
    Oct 14, 2026, 6:37 PM

    @cliffle do you reckon it would be fast enough to generate 4k/120Hz display test patterns? With whatever wire protocol modern TV panels use, apparently it's embedded DP these days?

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  • clifflecliffle@hachyderm.io
    Oct 14, 2026, 6:18 PM

    @musicmatze that is my beloved Keychron K3 Pro with low profile "brown" semiclicky switches. It's great, runs open QMK, battery lasts forever, and is currently configured to show rainbow LED ripples as I type because I am a Serious Adult.

    Not shown is my DEFT Pro wireless trackball, which is critical for portable CAD'ding, and I mostly love it but it has arguably the world's worst scrollwheel.

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  • Dion Dokterdiondokter@fosstodon.org
    Oct 14, 2026, 9:14 PM

    @cliffle man, I should design some electronics again. Been a while. I'm also not very good at it, but it is fun!

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  • Ryanfullywoolly@mastodon.social
    Oct 15, 2026, 11:27 PM

    @cliffle looks like a good setup. I'd miss the schematic tie-in, but ya very serviceable.

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  • clifflecliffle@hachyderm.io
    Oct 15, 2026, 11:29 PM

    @fullywoolly I'm using tabs in Sway, schematic is the next tab over, so it's quick to hop back and forth

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  • Ryanfullywoolly@mastodon.social
    Oct 15, 2026, 11:34 PM

    @cliffle it has everything I loved about kitty and more. Seriously need to give tiling wm a go again.

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