protoMIDI

protoMIDI is a compact DIY macropad with the physical language of a small MIDI controller: four large illuminated push buttons, one rotary encoder with push action, and a small monochrome OLED status display.

Table of Contents

• Status
• Hardware
• Firmware
• Flashing
• Repository Layout
• Design Intent

Despite the controller-style hardware, the firmware target is ZMK keyboard firmware. The device presents as a keyboard/HID macropad, not as a MIDI device. DAW, transport, clip, track, or effects labels are default keymap choices, not a dedicated MIDI protocol layer.

Status

This repository contains the Rev A bare-controller design baseline. The hardware design, pinout notes, KiCad project, STEP assembly, assembly preview, and ZMK firmware config are tracked in the repo. The firmware is HID-only and targets a nice_nano_v2 compatible nRF52840 board with the protomidi ZMK shield.

Firmware support:

• nice_nano_v2 compatible nRF52840 board target
• protomidi ZMK shield
• 2x3 GPIO switch matrix with five populated positions
• Four PB86 momentary buttons
• Encoder push switch as the fifth matrix key
• EC11-style rotary encoder
• 128x64 SSD1309 OLED on I2C using Zephyr's SSD1306-compatible driver
• Custom monochrome protoMIDI OLED status graphic
• USB HID keyboard
• Bluetooth HID keyboard through the selected ZMK board target
• Local UF2 firmware build

Hardware

Rev A hardware:

• nRF52840 Pro Micro style development board compatible with the nice_nano_v2 ZMK target
• Four PB86-B1 momentary switches with single-color LEDs
• One EC11 vertical rotary encoder with push switch
• One 2.42 inch 128x64 SSD1309 I2C OLED display
• One 3.7 V 1200 mAh protected LiPo battery with JST-PH connector
• Custom KiCad PCB files
• Bare assembly STEP export

Useful docs:

• Hardware configuration
• Component resources

Firmware

Firmware lives under firmware as a nested ZMK user config inside this larger hardware repository.

The firmware scope is intentionally HID-only:

• USB keyboard/HID output
• Bluetooth keyboard/HID output
• Media-key bindings for playback and volume
• No USB MIDI, BLE MIDI, DAW protocol, sequencer, clock, or control-change layer

Build locally from the repository root:

./firmware/build-local.sh

The default output is:

firmware/build-out/protomidi-nice_nano_v2.uf2

Double-tap reset on the nRF52840 board to enter the UF2 bootloader, then copy the generated .uf2 file to the mounted bootloader drive.

The default key behavior is:

Control	Binding
PB86-1	Play/pause
PB86-2	none
PB86-3	Previous track
PB86-4	Next track
Encoder push	Mute
Encoder clockwise	Volume up
Encoder counter-clockwise	Volume down

See firmware/README.md for build dependencies and firmware details.

Flashing

1. Install Docker.
2. Run ./firmware/build-local.sh from the repository root.
3. Double-tap reset on the nRF52840 board to enter the UF2 bootloader.
4. Copy firmware/build-out/protomidi-nice_nano_v2.uf2 to the mounted bootloader drive.
5. Let the board reboot, then test the controls over USB HID.
6. Pair the device over Bluetooth through the normal ZMK/nRF52840 host pairing flow when wireless testing is needed.

Repository Layout

firmware/   ZMK config, local build script, and generated UF2 output
hardware/   Pinout, KiCad files, CAD assembly, and Rev A hardware notes
resources/  Source references, images, datasheets, and component notes

Design Intent

protoMIDI should be reproducible from off-the-shelf parts and simple fabrication. Equivalent parts are welcome when they preserve the same electrical interfaces: momentary SPST switches, single-color LEDs, quadrature encoder, 3.3 V I2C OLED, and a Pro Micro compatible nRF52840 board supported by ZMK.

The PB86 LEDs are hardwired to 3V3. Firmware does not dim them, turn them off individually, or represent per-button LED state.