Key Features • Video Demo • Connecting Keybits • PCB • Case • Credits • License
keybytes-demo.mp4
Typing over USB:
demo2.mp4
- 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
Going around a keybit, the pogo pins on the N and W sides are 3.3V, SDA, GND, SCL and on the E and S sides they are SCL, GND, SDA, 3.3V. So two keybits only work together when an N or W side touches an E or S side, which gives every joint two ways a keybit can be turned and still work: the usual way, or a quarter turn so the other matching side faces its neighbour. The left and top of the keyword take an E or S side and the right takes an N or W side.
If every keybit is the same way round any shape works, like a square with the keyword in one corner. A keybit turned the wrong way gets 3.3V on its SCL and GND on its SDA, so it gets no power and nothing behind it shows up until it's turned.
Status LED:
- White idle
- White fast blinks a keybit joined, touching the keyword or further out
- Blue flashing the keybit on the programming pins
- Green blinks then green that keybit is flashed or already up to date
- Solid red flashing it gave up
- Red blinking a keybit on the keyword is turned the wrong way
- Red double blink a keybit somewhere has a neighbour turned the wrong way
Updating keybits: the keyword carries the keybit firmware. After updating the keyword, put every keybit on the programming pins once and wait for green. Keybits on different firmware versions don't talk to each other, so do all of them.
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
- JLCPCB for PCB fabrication and assembly
- 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 ·