Key Features • Video Demo • PCB • Case • Credits • License

• Rearrangeable layout where every key is its own 1u PCB
• CH32V003 RISC-V microcontroller on every key
• STM32WB55RGV6 main board with Bluetooth and USB
• Pogo pins on all 4 sides of every key for power and I2C
• Magnetic cases to hold the modules together
• Key programming from the main board over pogo pins
• 2MB QSPI flash (W25Q16JV) to store the key firmware
• Battery charging with the BQ25895 and solder pads for a 1S LiPo
• Buck-Boost converter (TPS631000)
• RGB status LED
• USB-C with ESD protection
• Ceramic Bluetooth antenna

Designed in KiCad! There are two boards, the Keybit and the Keyword, and both are 1u (19.05mm x 19.05mm).

A single key with a Cherry MX switch and a CH32V003. Every side has pogo pins for 3.3V, GND and I2C so it can connect to the keyword or to other keybits, and the pads on the corners are for programming.

Schematic:

Layout:

The main board that the keybits connect to. It is split into two PCBs that stack on top of each other. The top one has the STM32WB55RGV6, the antenna and the flash, and the bottom one has the USB-C, the charger and the buck-boost converter. The 3 pogo pins on the top are for programming the keybits.

Schematic:

Layout:

3D View:

Custom designed cases in Onshape, the STEP files are in the cad folder.

This project uses:

• KiCad
• OnShape for case design
• Blender for 3D renders
• STM32CubeMX
• Hack Club Forge

• Ember - A USB-C powered reflow hotplate with Bluetooth
• Cyberboard - A Raspberry Pi Pico-sized STM32 development board with Bluetooth
• Trace - A comprehensive PCB ruler with reference footprints
• Linea - An EMR tablet

MIT

notaroomba.dev  ·  GitHub @NotARoomba  ·