Kiai

Kiai Wireless Split Keyboard

Features

• Seeed Studio XIAO nRF52840
• ZMK
• 34-keys
• low profile Choc v1

Requirements

• Seeed Studio XIAO nRF52840 (2)
• Choc v1 switche (34)
• 1N4148 SOD-123 (34)
• 2 pcbs (gerbers and kicad files shared in this repo)
• 3.7v lipo batteries (2)

Build Notes

Because I wanted to have the xiao modules both facing up so the built-in reset button on the xiao is readily accessible, there are a couple of things that may be different from how other boards are normally set up.

For the left hand side, need to jumper the bottom two holes as shown below:

The right side will also need the jumper but on the upper two holes instead:

The diodes should mirror the orientation on the opposite board.

Flashing the Firmware

For convenience, the compiled uf2 files are in the bin folder. left.uf2 -> for the left side right.uf2 -> for the right side reset.uf2 -> can be flashed to both boards to reset. I found this useful when the slave side is not pairing with the master side.

How to upload the firmware to your board:

• Connect one keyboard to your computer via USB
• Double-click the reset button on the xiao module on the left board. When the XIAO-SENSE folder appears, copy over left.uf2 onto that folder. It will automatically eject after.
• Do the same to the right keyboard, this time flashing the right.uf2 file.
• TIP: immediately after flashing try to put the keyboard into bootloader mode. This prevents it from trying to pair before you are ready. Re-activate the two sides at the same time; this usually helps when you find the slave side does not register keystrokes.

Building/Compiling your own firmware

• install ZMK following this guide: ZMK Basic Setup

• in your {zmk-dir}/app/board/shields directory, create a folder named kiai

• copy the files in the zmk folder in this repo into your new kiai directory

• compile the hex file for your left board using

  west build -p -b seeeduino_xiai_ble -d build/kiai/left -- -DSHIELD=kiai_left

• this will create a zmk.uf2 file in {zmk-dir}/app/build/kiai/left/zephyr

• use this file to flash the left-side board

• compile the hex file for your right-side board using

  west build -p -b seeeduino_xiai_ble -d build/kiai/right -- -DSHIELD=kiai_right

• this will create a zmk.uf2 file in {zmk-dir}/app/build/kiai/right/zephyr

• use this file to flash the right-side board