2 layers148.6 × 136.1 mm Left board, the printed circuit board in 3D

Left board

The Repo for IEEE-CPP's keyboard project

Size: 148.6 × 136.1 mm
Copper layers: 2
Thickness: 1.6 mm
Parts: 71
Nets: 52
Pads: 445
Tracks, vias: 502, 1
Routed: Yes
KiCad: KiCad 9.0 (file 20241229)
Created: 12 Mar 2026
Updated: 29 Mar 2026

Overview

Left board is an open-source printed circuit board by IEEE-CPP, from the IEEE-CPP/keyboardProject repository on GitHub, published under the GPL-3.0 licence. It is a 2-layer board of 148.6 × 136.1 mm with 71 parts on 52 nets, routed with 502 tracks and 1 via.

Its parts include 32 diodes and 30 switches. It belongs with the keyboards and input boards of this library.

README

README.md

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

text

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:

bash

ergogen splitKeyboard/ergogen/ --output build/

Nix (optional)

For users with Nix installed:

bash

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

Generate PCB files (see Development Setup above)
Open splitKeyboard/kicad/ in KiCad to generate Gerbers
Order PCBs from your preferred manufacturer
Solder components:
- Diodes (observe polarity)
- Hotswap sockets
- TRRS jack
- Reset button
- OLED display
- Pro Micro header pins (or socket)
Flash firmware using QMK or ZMK

Firmware

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

License

GNU General Public License v3. See LICENSE for details.

Credits

Ergogen - Keyboard layout generator
KiCad - PCB design software

Parts

Qty	Value	Footprint	References
32		ComboDiode	D1, D2, D10, D11, D12, D13, D14, D15, D16, D17, D18, D19, D20, D21, D22, D23 +16
30		PG1350	S1, S2, S10, S11, S12, S13, S14, S15, S16, S17, S18, S19, S20, S21, S22, S23 +14
5		ceoloide:mounting_hole_npth	MH1, MH2, MH3, MH4, MH5
1		E73:SW_TACT_ALPS_SKQGABE010	B1
1		ProMicro	MCU1
1	OLED	lib:OLED_headers	OLED1
1	TRRS-PJ-320A-dual	TRRS-PJ-320A-dual	TRRS1

Questions

How big is the Left board PCB?

It measures 148.6 × 136.1 mm and has 2 copper layers, 1.6 mm thick.

What parts does the Left board use?

71 parts. The full list of its parts is on this page, with links to each part's symbol and footprint where PCBKit's library has them.

Where can I download the Left board KiCad files?

From the IEEE-CPP/keyboardProject repository on GitHub, at the commit this page was made from: the board is splitKeyboard/kicad/left_board.kicad_pcb. PCBKit opens the board in the browser, with nothing to install.

Can I use the Left board design in my own project?

Its repository publishes it under the GPL-3.0 licence: you may reuse it on that licence's terms (keep the author's notice, and for a copyleft licence share your changes alike).

Category and platform

Keyboards and input

Project files

Show this board on your page

A live frame, for any web page

<iframe src="https://pcbkit.io/embed/boards/ieee-cpp-keyboardproject" title="Left board in PCBKit" width="100%" height="480" style="border:0;border-radius:12px" allow="fullscreen" loading="lazy"></iframe>

A picture

<img src="https://pcbkit.io/embed/boards/ieee-cpp-keyboardproject.jpg" alt="Left board" width="1200" height="900">

A picture that opens the board, for a README

[![Left board](https://pcbkit.io/embed/boards/ieee-cpp-keyboardproject.jpg?size=s)](https://pcbkit.io/boards/ieee-cpp-keyboardproject)

Source

Repository: IEEE-CPP/keyboardProject
Board file: splitKeyboard/kicad/left_board.kicad_pcb
Commit: a5ed806
Licence: GPL-3.0
Copies: 2 copies in 1 repository

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