Mad_RP2040

A small RP2040-based keypad PCB. Originally a minimal 2-key board to build confidence with the RP2040 ahead of a full-size keyboard, it has since grown into a 4x4 "anything" keypad with a rotary encoder and per-key RGB.

Status: Rev B (4x4) — fabricated November 2025; controller, USB and SK6812MINI-E chain verified, but a matrix wiring error past row 1 / col 1 needs cut-and-bodge to fix on existing units. The fix is not yet in main, so fabbing from main today reproduces the same bodge. Rev A (2-key) was fabricated and tested; archived under resources/rev_a/.

The encoder footprint is on the board but has not yet been populated/tested.

Hardware

• MCU: Raspberry Pi RP2040 (QFN-56)
• Flash: W25Q128JV (16 MB QSPI)
• Clock: 12 MHz ECS-2520MV SMD oscillator
• Power: USB-C input, NCP1117-3.3 LDO, ECMF02-2 common-mode filter / ESD protection
• Switches: 16x Kailh Choc v2 hotswap (12 mm) in a 4x4 matrix with 1N4148W diodes
• Encoder: 1x EC12 rotary encoder with switch
• Lighting: Per-key SK6812MINI / SK6812MINI-E RGB LEDs
• Split support: TRS interlink (JST-SHL/GH connectors) plus a solder-jumper hand-detect selector
• Programming: ARM SWD via Tag-Connect TC2030-NL footprint

Datasheets for the major parts live in resources/datasheets/.

Repository layout

Mad_RP2040.kicad_pro     # KiCad project
Mad_RP2040.kicad_sch     # Top-level schematic
Mad_RP2040.kicad_pcb     # Board layout
Mad_RP2040.kicad_dru     # Design rules
Controller_RP2040.kicad_sch
MCU_RP2040.kicad_sch
Switches.kicad_sch       # Hierarchical sheets
localLib.pretty/         # Project-local footprints
mad_lib/                 # Submodule with shared symbols/footprints
resources/               # Datasheets, enclosure STEP, fabrication outputs
build-panel.yaml         # KiBot panel config (1x2)
options.yaml             # KiBot global options

The repo uses a git submodule for mad_lib; clone with:

git clone --recurse-submodules https://github.com/Cimos/Mad_RP2040.git

Build & CI

GitHub Actions in .github/workflows/ drive the build via Cimos/kibot-config:

• build-pcb-action.yaml — fabrication outputs (gerbers, drills, BOM, position files)
• build-images-action.yaml — 2D top/bottom renders
• build-cad-action.yaml — STEP / 3D CAD export
• build-panel-action.yaml — KiKit panelization (2 cols x 1 row, see build-panel.yaml)
• build-diff-action.yaml — visual diff against the base branch
• build-video-action.yaml — turntable / fly-through video

Each workflow uploads its results as a GitHub Actions artifact on every push.

Firmware

Keymap and configuration are kept in separate repos:

• Cimos/qmk_config — QMK keymap
• Cimos/zmk-config — ZMK keymap

Enclosure

FreeCAD-exported cases live in resources/enclosures/:

• MadRP2040 2-Key Case.step — Rev A test board
• MadRP2040 Anything Case.stl — Rev B 4x4 anything keypad

Released board CAD (STEP) snapshots live under resources/rev_a/.

Renders

Generated by the build-images, build-cad and build-panel workflows from the latest main.

License

Released under the MIT License. Copyright (c) 2023 Simon Maddison.