geekhack Projects > Making Stuff Together!
Need a 27-pin controller recommendation
jfloren:
I'm assembling my first homebrew keyboard. The matrix is going to be 8 rows and 19 columns, so I need a QMK-compatible microcontroller with at least 27 usable I/O pins. Any recommendations? A USB-C connector would also be a nice-to-have, but the main thing is finding a solid controller with enough pins.
fpazos:
A Teensy. Also you can save 2 pins using a 13x12 matrix..
Enviado desde mi 23122PCD1G mediante Tapatalk
TomahawkLabs:
As someone also looking into a solution like this, there are no "great" options for handwiring a full size keyboard anymore now that the Teensy ++ 2.0 is out of production. I was able to find this solution: the ProS3, which is ESP32 based.
There just isn't much of a market for a MCUs with 25+ GPIO pins that can be used. Ideally there would be a company that has a RP2040 built out with all the GPIO including breakouts for the USB, but niche hobbies are niche. Hopefully the ProS3 meets your needs.
jfloren:
Thank you both for your suggestions... I'll also look at the matrix a bit more and see if there's any way I could consolidate rows or columns without making a wiring nightmare. If I can just reduce one pin, I could use a Raspberry Pi Pico
https://i.imgur.com/EEHtC7R.png
TomahawkLabs:
I can try to find some time today to replicate your matrix, but yeah I can see you have a few columns with only 3-4 keys in it. You will 100% need to reorganize the matrix. I think there is a bit of improvment that can be done there. The biggest thing off the bat is moving the 4 keys below the space up into row 6. That will get rid of at least 1 pin. Please post the RAW for KLE and I can play with the matrix to see if we can simplify it. :)
Here is my handwired project.
Also are you looking to hand wire or to create a PCB because if you are handwiring it will be much harder than a custom PC for "wild" trace routing. You can see how many wires are in my build and they all go up/down or left/right. I don't have any funky wiring to make it as efficient (low GPIO) as possible.
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