m20 — 5×4 LEGO Macropad / Numpad

A versatile 5×4 ortholinear macropad / numpad mounted on a 16×16 LEGO baseplate, supporting both 5-pin Cherry MX and low-profile Kailh Choc v2 switches, plus an optional rotary encoder, I²C OLED screen, and RGB LED strip.

Status: Tested All OK

* [x] Gerbers designed
* [x] Firmware
* [x] Breadboard tested
* [x] Gerbers printed
* [x] Board tested

Features

• Layout: 5×4 ortholinear (20 keys)
• Switches: Dual footprint supporting 5-pin Cherry MX and Kailh Choc v2 switches
• Controller: Raspberry Pi Pico (RP2040) or compatible clones (WeAct, Teenstar)
• Peripherals: Optional EC11 rotary encoder, I²C OLED display, status LED, and 3-pin RGB LED strip
• Diodes: Supports both through-hole (DO-35) and surface-mount (SOD-123) 1N4148 diodes
• Firmware: QMK

3D Render & PCBs

3D Render

Printed PCB (Front & Bottom)

BOM

• 1× RP2040 Raspberry Pi Pico or compatible clone (WeAct, Teenstar)
• 2× 20-pin DIL/DIP sockets and matching headers
• 20× 1N4148 signal diodes (DO-35 through-hole or SOD-123 SMD)
• 20× 5-pin Cherry MX or Kailh Choc v2 switches
• 1× EC11 rotary encoder (optional)
• 1× 510 Ω resistor + 1× status indicator LED (adjust resistor value for desired LED brightness)
• 1× I²C OLED display (optional)
• 3-pin addressable LED strip (optional)
• LEGO 16×16 baseplate and perimeter bricks/tiles

Case & Assembly

• LEGO Enclosure: See the m65 Case & Thickness section.
• Soldering & Build: Follow the step-by-step Assembly Guide.

Gerbers & KiCad

Full KiCad project files and Gerbers are available in the m-lego/m20 GitLab repository, using shared symbols and footprints from m-lego/m65.

Firmware

git clone --recurse-submodules -b mlego https://github.com/alinelena/qmk_firmware.git qmk-alin
cd qmk-alin
qmk compile -kb mlego/m20/rev1 -km default

# or using make:
make mlego/m20/rev1:default

Pinout Reference

• Columns (C0–C3): GP1, GP6, GP7, GP8
• Rows (R0–R4): GP9, GP10, GP11, GP12, GP13
• Encoder: Pad_A = GP4, Pad_B = GP5
• OLED (I²C): SDA = GP2, SCL = GP3

Build Gallery