KMK

Mechanical keyboard firmware for humans (and ARM microcontrollers)

KMK is a work-in-progress and proof-of-concept firmware for (usually mechanical) keyboards, written in MicroPython and CircuitPython. This allows for high-level and expressive keyboard programming and creature comforts that C simply doesn't make easy. KMK was heavily inspired by QMK - in fact, KMK was only created because QMK didn't correctly support some hardware I bought, and hacking support in was going to be a heavy uphill battle.

This project is currently written and maintained by Josh Klar and Kyle Brown.

Supported Devices

Board	Chipset	Python Platform	Notes
pyboard v1.1	STM32F405RG (Cortex M4F)	MicroPython	A very basic keyboard has been written for this, see boards/klardotsh/threethree_matrix_pyboard.py

Support Planned/WIP

Board	Chipset	Python Platform	Notes
Seeed nRF52840 Micro Dev Kit	nRF52840	MicroPython	This is basically as bleeding edge as it gets. Linked is my very unstable and somewhat broken uPy port to this device, WIP. Supports BLE HID and, allegedly, USB HID if I can figure it out. Another option is CircuitPython, since AdaFruit is working on a Feather Express with the same chipset, and commits have been made there to support USB HID.
Planck rev6 Keyboard	STM32 of some sort	Probably MicroPython?	I have one on the way! We'll see what happens.
Proton C Controller?	???	???	Does not exist yet, the controller from a Planck rev6 in a Pro Micro pin-compat controller chip

Iffy Devices

Board	Chipset	Python Platform	Notes
Adafruit HUZZAH32	ESP32	MicroPython	In theory this may work as a BLE HID device, or with a GPIO-based USB breakout. Right now, we haven't written the code for this device. Built-in USB port can't run in HID at all.
Adafruit Feather nRF52 BLE Controller	nRF52832	CircuitPython	Lack of USB HID (HW), but could be fixed with GPIO USB breakout. BLE HID could be possible, but it's considered somewhat unstable. This chip is considered "mostly unsupported" in CircuitPython according to Adafruit Discord, so I've mostly abandoned it for now.

Unsupported Devices

If you don't see it in "Supported Devices", it won't work out of the box, it's basically that simple. Pull requests are welcome and encouraged to add support for new keyboards. The base requirements for device support are a port of CircuitPython or MicroPython, at least 256KB of flash storage, and USB and/or Bluetooth LE interfaces.

Here's a list of boards that seem like they should otherwise be supported, but are currently not, due to some deficiency uncovered in development/testing:

Board	Chipset	Python Platform	Reason Unsupported
Adafruit Feather Huzzah	ESP8266	CircuitPython	Suuuuuper limited on GPIO lanes, Lack of USB HID (HW)
Teensy 3.2 Controller		MicroPython	Lack of USB HID (SW - MP)

The Great Hackaround

While it is required that at least the device talking over USB/BLE HID (the "primary brain") be from the Supported Devices list and running the primary component of KMK, it will soon be possible to build split keyboards with other, otherwise unsupported devices (currently this means a Pro Micro), either to reduce costs or to convert existing QMK boards to KMK. You'll need to flash "dummy" firmware to each Pro Micro which simply scans a matrix and passes the values over I2C to the "brain" device, which does the heavy lifting from there (including actually sending HID events).

The obvious downsides of this method are increased number of moving parts, increased number of things to flash (though the Pro Micros only need flashed when matricies change, which should almost never happen once a board is built), and all downsides that go with those points (increased power usage, etc.) The upside is that it can be a ton cheaper to build a split keyboard this way - cheapo Pro Micro clones can be had for as little as $4 CAD at time of writing, whereas a HUZZAH32, for example, is closer to $26 CAD, and to build the "traditional" way, you'd need N of them (where N is the number of split sections of your keyboard).

It is also possible to convert many QMK boards through this fashion - while untested for now, just about anything with a TRRS jack should work (Ergodoxen, just about anything from keeb.io, etc.)

This hackaround is almost certainly pointless for non-split boards.

License, Copyright, and Legal

This project, and all source code within (even if the file is missing headers), is licensed GPLv3 - while the tl;dr is linked, the full license text is included in LICENSE.md at the top of this source tree.

When contributing for the first time, you'll need to sign a Contributor Licensing Agreement which is based on the Free Software Foundation's CLA. The CLA is basically a two-way promise that this code is and remains yours, but will be distributed as part of a larger GPLv3 project. If you'd like to get it out of the way early, you can find said CLA here. If you forget, the bots will remind you when you open the pull request, no worries!