Tiny18

Tiny18 is a compact, 18-key wireless split keyboard designed for Japanese input. Each half uses a Seeed Studio XIAO nRF52840 and ZMK firmware.

日本語の説明は README.ja.md を参照してください。

Download the latest firmware · Firmware source · Keymap

• 18 keys total (9 per half)
• Wireless split using Bluetooth Low Energy
• Seeed Studio XIAO nRF52840 controllers
• Kailh Choc (PG1350) switch footprints
• Diodeless, direct-pin wiring
• Reversible PCB: the same board is used for both halves
• Battery connector and hardware power switch on each half
• ZMK Studio support on the right/central half over USB

This repository contains the production outputs for the PCB. The ZMK source and downloadable UF2 firmware are kept in the separate zmk-config-tiny18 repository so that firmware builds remain small and reproducible.

See production/README.md before ordering boards.

Prebuilt firmware is distributed from the firmware Releases page. A release contains:

• tiny18-right.uf2 — right half and Bluetooth central
• tiny18-left.uf2 — left half and Bluetooth peripheral
• settings-reset.uf2 — clears saved Bluetooth and split settings
• SHA256SUMS — checksums for the UF2 files

The right and left files are not interchangeable. Flashing the wrong file will not normally damage the controller; enter the bootloader again and flash the correct file.

1. Turn the keyboard's battery power switch off. Connect one half to the computer with a USB data cable.
2. Double-press the XIAO reset button. A drive named XIAO-SENSE should appear.
3. Copy the matching UF2 file to that drive:
   • right half: tiny18-right.uf2
   • left half: tiny18-left.uf2
4. Repeat for the other half, then disconnect USB and turn both halves on.
5. Pair the Bluetooth device named tiny18 from the host computer.

For first-time setup, or when the halves no longer pair, flash settings-reset.uf2 to both halves first. Enter the bootloader again, then flash the matching right and left firmware.

After clearing settings, remove the old tiny18 entry from the host's Bluetooth settings before pairing again.

• Verify battery polarity before connecting a LiPo battery. Reversed polarity can damage the controller or battery.
• Turn battery power off while flashing over USB.
• These files are provided as-is. PCB fabrication, assembly, battery selection, and physical testing remain the builder's responsibility.
• The repository does not currently include a case or switch plate.

The hardware production files in this repository are licensed under CERN-OHL-P-2.0; see NOTICE. Firmware is licensed separately under the MIT License in the firmware repository. Third-party components retain their own licenses.