4 layers234 × 84 mm
Main panel
google/mozc-devices
Circuit diagrams and firmware source code for Gboard DIY keyboards
234 parts3kApache-2.0
2 layers168 × 113 mm
Octa chord
wldd22/octa-chordA 12-key MIDI keyboard with rotary encoders, key switches, and capacitive touch pads.
- Size
- 168 × 113 mm
- Copper layers
- 2
- Thickness
- 1.6 mm
- Parts
- 17
- Nets
- 37
- Pads
- 122
- Tracks, vias
- 149, 13
- Pours
- 1
- Routed
- Yes
- KiCad
- KiCad 10.0 (file 20260206)
- Created
- 22 Oct 2026
- Updated
- 5 Nov 2026
Overview
Octa chord is an open-source printed circuit board by wldd22, from the wldd22/octa-chord repository on GitHub. It is a 2-layer board of 168 × 113 mm with 17 parts on 37 nets, routed with 149 tracks and 13 vias.
It is built around the SK6812MINI-E. Its parts include 8 switches, 6 diodes, 2 ICs and 1 connector. It belongs with the keyboards and input and audio and music boards and the ESP32 boards of this library.
Main components
1README
README.mdOcta Chord
A 12-key MIDI keyboard with rotary encoders, key switches, and capacitive touch pads.
Details
PCB made in KiCad
Firmware in KMK
Components:
- Waveshare ESP32-S3-Zero: Microcontroller
- MPR121 Breakout V12: Capacitive Touch Sensor Control Module
- Kailh Choc v1 Switches: Key switches
- Chocfox CFX Choc Blank Keycaps: Keycaps
- Hongyan EC11H 7CE20P1ZD20: Rotary encoders
Features:
- 12 capacitive touch pad keys, one octave on a piano
- 6 key switches in a 3x2 grid, each with an LED
- 2 rotary encoders with switches
- ESP32 microcontroller with a USB-C port and 15 GPIO pins
About
Before making this project, I barely knew anything about MIDI, but I was curious to learn how it worked and use it to make simple music. So, for week 3 (Music week) of Hack Club's Half Life, I was excited to make a simple MIDI controller I could use and learn from.
My original plan was far more ambitious than the final version. See JOURNAL.md for some of the many iterations I went through of the layout and overall design. I had to make many compromises and changes so the final product was useful, feasible, and something I could be happy with.
Images
Schematic
PCB Routing
Parts
17| Qty | Value | Footprint | References |
|---|---|---|---|
| 6 | SK6812MINI-E | LED_SMD:LED_SK6812MINI-E_3.2x2.8mm_P1.5mm_ReverseMount | D1, D2, D3, D4, D5, D6 |
| 6 | SW_Push | Hackclub Footprints:Kailh Choc Low-Profile Switches | SW1, SW2, SW3, SW4, SW5, SW6 |
| 2 | RotaryEncoder_Switch_MP | Rotary_Encoder:RotaryEncoder_Alps_EC11E-Switch_Vertical_H20mm | SW7, SW8 |
| 1 | Capacitive Touch Pads | Capacitive Pads:Capactive Key Octave | J1 |
| 1 | MPR121_Breakout_12Pin | MPR121:MPR121_Breakout_12Pin | U2 |
| 1 | Waveshare ESP32-S3-ZERO | Hackclub Footprints:Waveshare ESP32-S3-Zero | U1 |
Questions
How big is the Octa chord PCB?
It measures 168 × 113 mm and has 2 copper layers, 1.6 mm thick.
What parts does the Octa chord use?
17 parts, built around the SK6812MINI-E. 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 Octa chord KiCad files?
From the wldd22/octa-chord repository on GitHub, at the commit this page was made from: the board is pcb/octa-chord.kicad_pcb and its schematic pcb/octa-chord.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Can I use the Octa chord design in my own project?
Its repository states no licence, so its author keeps all rights: ask wldd22 before reusing the design.
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