Macro keypad

Macro Keypad

A 3×3 hot-swap USB-C macro keypad built around an RP2040, with per-key RGB and a rotary encoder. Designed in KiCad from schematic through fabrication.

Top	Bottom

Bare 2-layer board from JLCPCB, before assembly.

Hardware

• RP2040 (QFN-56) with a 12 MHz crystal and a W25Q16JV 2 MB QSPI flash
• USB-C receptacle for power and data, with 5.1 kΩ CC pulldowns
• AP2112K-3.3 LDO dropping USB 5 V to the 3.3 V rail
• 3×3 key matrix on Kailh MX hot-swap sockets, one SOD-123 diode per key so simultaneous presses don't ghost
• 9× WS2812B addressable RGB, daisy-chained as one data line for per-key backlight
• EC11 rotary encoder with integrated push switch
• BOOTSEL and RESET buttons, plus a 4-pin SWD header for debugging
• Decoupling on every supply pin per the RP2040 hardware design guide
• 2-layer board, ERC and DRC clean, fabricated by JLCPCB

Full component list: docs/bom.csv — 70 parts across 19 line items. Schematic as PDF: docs/schematic.pdf.

Layout

hardware/      KiCad project — schematic, board, and project-local footprint library
fabrication/   Gerbers and drill files as sent to the fab, plus the board outline DXF
docs/          Schematic PDF, BOM, board photos

hardware/keyswitches.pretty holds the Kailh hot-swap footprint and is wired up through hardware/fp-lib-table, so the project opens with all footprints resolved on a clean KiCad install.

Building the board

Open hardware/macro-keypad.kicad_pro in KiCad 10. To re-order boards, zip the contents of fabrication/gerbers/ and upload — 2 layers, 1.6 mm, HASL is fine.

Status

The board is fabricated and I'm hand-soldering the switches, diodes, and supporting components. Firmware is in progress: a USB HID keyboard with matrix scanning and debounce on the RP2040. Bring-up and testing come once assembly is done.

Known gaps for a v2

• No ESD protection on the USB data lines. A USBLC6-2SC6 across D+/D− is the obvious addition and there's room for it near the connector.
• The matrix diodes are specified only as generic D in SOD-123. They need a real part number in the BOM (1N4148W or equivalent) before anyone else can build this.