Openmicro

OpenMicroKbd

An open-source hardware recreation of OpenAI's Codex Micro macropad — 13 low-profile keys, a rotary encoder, an analog joystick, a capacitive touch pad, and per-key + underglow RGB on a wired USB-C board built around an STM32F072.

The finished board — read the launch post for the full story.

The PCB is written, not drawn. The entire schematic is source code in CoHDL, an open-source, AI-native hardware description language. The compiler type-checks the design — units, pin-connection obligations, power integrity — and emits the netlist, BOM, footprints and layout constraints you can inspect under hw/v1/out/.

🌐 https://openmicrokbd.org · 🖨️ Printable case on MakerWorld (中国站) · License: MIT

Designed in CoHDL

This board was designed in CoHDL, an open-source hardware description language that makes schematic (PCB) design AI-native: a board is a program — typed, checked, and compiled. In CoHDL, the design in hw/v1/src/ is the schematic; the compiler is the oracle that grades it.

CoHDL is open source. Visit cohdl.org to explore the language, or browse and contribute to the compiler and libraries on GitHub. This repository also checks in the complete compiler outputs under hw/*/out/, so the generated hardware design remains directly inspectable.

Questions about CoHDL, the hardware source, or building a board of your own? Join the CoHDL and OpenMicroKbd community on Discord.

What's inside

Hardware (v1)

• MCU: STM32F072CBT6 (Cortex-M0), 8 MHz HSE crystal, 2×3 SWD debug socket
• Keys: 13× Kailh Choc V2 low-profile switches on a 19.05 mm grid (square 4×4-cell frame, matching the Codex Micro layout), 1N4148W per-key matrix diodes
• Inputs: EC11 rotary encoder, RKJXV analog joystick, capacitive touch pad
• Lighting: 13× per-key SK6812MINI-E (reverse-mount, one WS2812 chain) + 8× perimeter underglow SK6812MINI-E (second chain)
• USB: Type-C wired, USBLC6 ESD protection, AP2112 3.3 V LDO
• PCB laid out from the CoHDL-generated constraints; manufacturing handoff via IPC-2581

Building

# Production firmware binary + debug ELF
scripts/build-firmware.sh dist

# Native GPUI macOS app bundle + DMG (ad-hoc signed for local testing)
scripts/package-macos.sh dist dist/openmicro-fw-<firmware-version>.bin

# Or run the companion app from source
cd app && cargo run --release --locked

On Windows, install Rust and Visual Studio's Desktop development with C++ workload, then build a portable package from PowerShell:

rustup target add x86_64-pc-windows-msvc
./scripts/package-windows.ps1 `
  -OutputDir dist/windows `
  -FirmwareBin dist/openmicro-fw-<firmware-version>.bin `
  -Target x86_64-pc-windows-msvc

Use aarch64-pc-windows-msvc for a native Windows on Arm package; that build also requires the Visual Studio LLVM/Clang component.

The open-source CoHDL compiler and its documentation are available at cohdl.org. Generated netlists, BOMs, footprints, and layout constraints remain checked in under hw/*/out/ for inspection and use without rerunning the toolchain.

Releases build Intel and Apple Silicon DMGs, Windows x64 and Arm64 portable ZIPs, and firmware through GitHub Actions. See RELEASING.md for versioning, Apple signing/notarization secrets, the required device smoke test, and the tag flow. Linux packaging, USB permissions, and the STM32F072 ROM-DFU host-controller workaround are tracked in docs/linux-firmware-updates.md.

Production files

The final routed v1 board lives in hw/v1/pcb/ (openmicro.kicad_pcb, opens in KiCad 9+). The manufacturing package — Gerber/drill zip, assembly BOM, and SMT pick-and-place CSV, ready to upload to a fab such as JLCPCB — is in hw/v1/fab/, with DRC status and ordering notes in hw/v1/fab/README.md.

Printing the case

The enclosure is published as a ready-to-print model on MakerWorld, alongside the editable Fusion sources in hw/v1/mechanical/:

• MakerWorld — OpenMicroKbd
• MakerWorld 中国 — OpenMicroKbd 开源键盘

The print covers the case, the rotary knob and the joystick cap, plus the solder-assembly jig and the shipping package as a bonus from the same project. Recommended settings: 0.4 mm nozzle, 0.2 mm layer height, 3 walls, 15–20% infill, PLA or PETG (PETG for a daily driver), no supports required.

Beyond the print you will need an assembled PCB, Choc V2-compatible keycaps, M2×4 female-female brass standoffs, M2×5 screws, and a USB-C cable.

License

MIT © 2026 Tony Huang. Build your own — attribution appreciated.

OpenMicroKbd is an independent open-source project and is not affiliated with, endorsed by, or sponsored by OpenAI. "Codex Micro" refers to OpenAI's product; all trademarks belong to their respective owners.