にぶんかつ ✦ Nibunkatsu comes from the Japanese word for splitting in half.
Nibunkatsu is a compact split keyboard for typing and programming. I'll be using the ESP32-S3 microcontroller with KMK firmware, featuring RGB under the keys, an OLED display on the left half, and a rotary encoder in the right half!!
This project was created as part of the Hack Club Blueprint program that empowers high school students to design and build real hardware projects.
Project Stats: ~70 hours over the course of 1 week of active work and learning!
- Split Design — 5x7 layout per half, including a number row
- RGB Underglow — 28 individually addressable WS2812C LEDs per half
- OLED Display — 0.91" display for layer status and other keyboard info
- Rotary Encoder — PEC11 encoder for volume control and maybe more?
- Hotswap Sockets — Simple switch replacement without constant soldering
- KMK Firmware — Programmable using Python
- TRRS Connection — A 3.5mm audio cable for split communication between both halves. Also with ESD protection, protecting the MCU's TX/RX pins.
├── firmware/ - KMK firmware code and configuration
├── PCB/ - EasyEDA PCB project files and schematics
├── CAD/ - 3D models for the keyboard case and plates (.3mf and .step)
└── assets/ - Work screenshots and photos
├── bom.csv - Bill of Materials with supplier links, prices and quantities
- Microcontroller: ESP32-S3-WROOM-1-N4R2
- Switches: Cherry MX compatible hotswap sockets (I'll be personally using Gateron Banana low profile switches)
- RGB LEDs: WS2812C-2020
- Display: 0.91" OLED (128×32 pixels)
- Encoder: PEC11 rotary encoder with 24 steps and push button
- Connection: TRRS cable for communication between halves
Check the PCB designs in here
The case was designed in Shapr3D with 4 printable models:
- Left case + Left plate
- Right case + Right plate
Bo th available in .3mf and .step formats positioned in the CAD/ directory!
3-layer configuration:
- Layer 0 (Base): QWERTY layout with a number row
- Layer 1 (Shortcuts): Some operating system shortcuts maybe
- Layer 2 (Navigation): Arrow keys and media controls
Written in Python using the KMK firmware framework.
The firmware source code is available in firmware/.
Total cost: €153.11
| Component Type | Part Name | Qty | Other Notes |
|---|---|---|---|
| Microcontroller | ESP32-S3-WROOM-1-N4R2 | 3 | MCU |
| Switches | Gateron Low Profile (Banana) | 54 | Tactile yet silent |
| Keycaps | PBT Low Profile | 1 | Double-shot PBT, getting shine-through letters |
| PCB Fabrication | Custom PCB | 5 | via JLCPCB |
| RGB LEDs | WS2812C-2020 | 55 | Per-key RGB underglow |
| Connectivity | TRRS Cable | 1 | Interconnect cable |
| Sockets | Kailh Hot-Swap Sockets | 100 | Solder-free switch replacement |
| Display | 0.91" OLED | 1 | 128×32 pixel status display |
| Controls | PEC11 Rotary Encoder | 1 | Volume control |
| Misc Electronics | Diodes, Capacitors, LDOs, Resistors | ~150 | Logic, power regulation, ESD protection |
The complete CSV with supplier links is available here: bom.csv
This project uses a three-part licensing model to appropriately protect hardware, software, and documentation.
| Component | License | Covers |
|---|---|---|
| Hardware | CERN-OHL-W-2.0 | PCB designs, schematics, mechanical CAD files |
| Firmware | MIT License | Python/KMK firmware and source code |
| Documentation | CC BY-SA 4.0 | Assets, photos, diagrams, written guides |
- Hardware (CERN OHL): Covers physical manufacturing rights and ensures attribution for derivative designs
- Firmware (MIT): Permissive software license allowing easy reuse and integration
- Assets (CC BY-SA): Ensures proper attribution for media assets and documentation
Note: Third-party project dependencies may have different licenses. Please refer to their respective repositories for licensing information.
Designed with 💙 by 𝕲𝕭
Special thanks to the Hack Club community for their support!