Split Keyboard

A custom split ergonomic keyboard designed with Ergogen and KiCad.

Keyboard Layout

• 5-column layout: outer, pinky, ring, middle, index, inner
• 5 rows: mod, bottom, home, top, num
• 3-thumb keys: layer, space, extra
• Column-based wiring with row diodes

Features

• Choc hotswap sockets (Kailh Choc low-profile switches)
• Pro Micro microcontroller (ATmega32U4)
• OLED displays (SSD1306, I2C)
• TRRS jack for inter-board communication
• ESD protection on TRRS data lines
• Reset button
• 3D printable case files (STL)

Files

splitKeyboard/
├── ergogen/
│   ├── config.yaml    # Ergogen configuration (layout, PCB definitions)
│   ├── footprints/    # Custom footprint definitions
│   └── output/
│       ├── cases/    # 3D printable case files (STL)
│       └── outlines/ # DXF files for CNC cutting
└── kicad/
    ├── left_board.kicad_pcb   # Left half PCB design
    └── right_board.kicad_pcb  # Right half PCB design

Development Setup

Manual (recommended)

Install ergogen from https://ergogen.xyz/install/, then generate PCBs:

ergogen splitKeyboard/ergogen/ --output build/

Nix (optional)

For users with Nix installed:

nix develop    # provides kicad + ergogen
generate       # runs ergogen (PCB + cases) and organizes output

Design Details

• Microcontroller: Pro Micro (5V, 16MHz)
• Key switches: Kailh Choc (low-profile)
• Diodes: 1N4148 (or similar)
• OLED: SSD1306 128x32 I2C
• Interconnect: TRRS cable (4-pole)
• ESD Protection: TVS diodes (PRTR5V0U2X or similar)

Pin Mapping

Column	Pin
outer	P21
pinky	P20
ring	P19
middle	P18
index	P15
inner	P14
thumb	P16
space	P10
extra	P9

Row	Pin
mod	P8
bottom	P7
home	P6
top	P5
num	P4

OLED

• SDA: P2
• SCL: P3

Building

1. Generate PCB files (see Development Setup above)

2. Open splitKeyboard/kicad/ in KiCad to generate Gerbers

3. Order PCBs from your preferred manufacturer

4. Solder components:

   • Diodes (observe polarity)
   • Hotswap sockets
   • TRRS jack
   • Reset button
   • OLED display
   • Pro Micro header pins (or socket)

5. Flash firmware using QMK or ZMK

Firmware

This repository only contains the hardware design. For firmware, use:

• QMK: https://github.com/qmk/qmk_firmware
• ZMK: https://github.com/zmkfirmware/zmk

License

GNU General Public License v3. See LICENSE for details.

Credits

• Ergogen - Keyboard layout generator
• KiCad - PCB design software