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Partycrasher Micro & Xiao

Semickolon shared some updates to the FAK firmware, along with Partycrasher Micro, a Pro Micro drop-in replacement.
Published March 25, 2024
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FAK, a keyboard firmware developed by semickolon aka mikoi14 for the cheap CH55x series MCUs, is now drop-in compatible with Pro Micro designs thanks to the newly implemented CH559L support.

Previously, FAK only supported CH552 chips (14 GPIOs at most), not enough for a Pro Micro replacement. Now, support has been added for CH559L which has over 40 GPIOs, way more than enough for a Pro Micro.

Pic: Partycrasher Micro

Partycrasher Micro

As a proof of concept and as a reference design, the author made Partycrasher Micro, a development board sporting the CH559L/CH558L with a footprint of a Pro Micro.

Compared to the Pro Micro, CH559L has a very minimal circuit that only requires TWO caps. No crystals, resistors, LDOs. This is amazing because this means diodeless 40% keyboards with integrated chip and very minimal circuit should now be possible with FAK! – semickolon.

True to the original concept of making keyboards as cheap as possible, the CH559L goes for $1.6 while the CH558L (virtually identical to CH559L except for flash size) goes for $1 on LCSC. You will likely find better deals elsewhere like on Aliexpress.

Other updates:

  • Duplex matrix support has been added. This makes it possible to have up to 98 keys with just the 14 GPIOs on a CH552T.
  • Rotary encoder support is also now implemented.
  • There's repeat key, sticky layers, analogue to ZMK's macro_pause_for_release, and transparent layer exit. Check out the GitHub readme for more info!

Lastly, if you also wanna take a look at the Seeed Studio Xiao drop-in replacement for FAK, here's the Partycrasher Xiao.

Pic: Partycrasher Xiao

Partycrasher Xiao

Due to how minimal the circuits are for these hand-solderable dev boards, it feels oddly satisfying to just make one on my own pretty quickly then slap it on a keyboard. I never expected I'd make my own dev boards and firmware when I got into this hobby, but, yep – mikoi14.


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Published on Mon 25th Mar 2024. Featured in KBD #159 (source).


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