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Karma

Karma is a 36-key wireless split ergonomic mechanical keyboard inspired by two very popular ergonomic keyboards: Corne and TOTEM.

Features

  • Ergonomic 36-key layout: A compact layout with 3x5 column-staggered keys, plus 3 thumb keys for each side.
  • Wireless first: Prioritizes a wireless split setup but can be used partially-wired by connecting the central side using USB-C.
  • Low-profile design: Engineered for a sleek, low-profile build that allows your palms to rest comfortably on the table while typing. This is achieved through the use of Kailh Choc switches and recessed cutouts for hot-swap sockets, reducing the overall case height (similar to the TOTEM keyboard), and using 1mm EVA foam instead of rubber feet.
  • Exceptional battery life: Has a battery life that is measured in weeks, not days.

Firmware

The Karma keyboard supports the ZMK open-source firmware. You can find my ZMK configuration for this keyboard in this repo.

Build Guide

Bill of Materials

To build the Karma keyboard, you'll need the following components:

Part Name Qty Remarks
2x SEEED XIAO BLE microcontrollers 2
Kailh Choc V1 low-profile switches 36 Low-profile mechanical switches
Keycaps compatible with Kailh Choc V1 36 MX-spaced keycaps are preferred for better fit
Hotswap sockets for Kailh Choc V1 36
SOD123 diodes 36
JST PH 2-pin SMD Header 2
301230 LiPo Batteries 2 Only 1 required for partially wired build
3D-printed case 2
M2 screws (5mm length) 8
M2 heat-set inserts (2mm height) 8
Self-adhesive EVA foam (1mm) - A slimmer alternative to rubber feet

Assembly

1. Order the Components

  • Zip up the gerber files for the left side and the right side.
  • Order the PCBs from a PCB prototype manufacturer like JLCPCB.
  • 3D print the STL files for the case in this repo.
  • All the other components are generic and can be found in Aliexpress.

2. Solder the Diodes

  • Solder the SOD123 diodes to the top of the PCB, paying attention to the polarity.
  • Apply solder to one pad, place the diode, and reflow the solder. Then solder the second pad.

3. Install the Hotswap Sockets

  • Solder hotswap sockets in place by first securing one pad, then ensuring they are properly seated before soldering the second pad.

4. Microcontroller Installation

  • Flash the firmware onto the SEEED XIAO BLE microcontrollers before soldering them to the PCB.
  • Place the microcontroller in the designated spot and solder the pads, starting with the corners to secure it, then solder the rest.

5. Connect the Batteries

  • Solder the JST PH 2-pin SMD Header to the PCB.
  • Check the polarity of the battery with a multimeter and connect the batteries to the JST header such that the red wire is connected to the positive (+) pad and the black wire to the negative (-) pad on the PCB.

6. Mount the Case

  • Insert M2 heat-set inserts into the screw holes in the 3D-printed case.
  • Place the PCB inside the case, ensuring the microcontroller and battery fit snugly.
  • Attach the two halves of the case using the M2 screws, securing them tightly.

7. Install the Keycaps and Switches

  • Insert the Kailh Choc V1 switches into the hotswap sockets, ensuring they click into place.
  • Attach your keycaps to the switches.

8. Add EVA Foam

  • Cut and apply self-adhesive EVA foam to the bottom of the case for added grip and cushioning.

9. Final steps

  • Once assembled, test the keyboard to ensure all switches and connections work.
  • If necessary, adjust the ZMK firmware for your specific keymap.

Congratulations! You've completed your Karma keyboard build.

License

This project is open-source and licensed under the CERN Open Hardware Licence Version 2 - Strongly Reciprocal License. See the LICENSE file for details.