J-Pad

A simple 4x4 handwired macropad with rotary encoder.

Requirements

Hardware

• 1x Raspberry Pi Pico
• 15x Cherry MX compatible switches
• 1x Rotary encoder (EC11)
• 16x 1N4148 diodes
• 4x 3M 10mm metal screws
• Wire for handwiring
• 15x Keycaps (any profile)
• MX encoder adapter: Thingiverse Thing:3770166

Software

• QMK Firmware (for customization)
• Computer with USB port

Tools (for assembly)

• Soldering iron and solder
• Wire strippers
• 3D printer or printing service
• Basic hand tools

Quick Start

Flash Firmware

1. Hold top-left key while plugging in USB
2. Copy firmware/jacco_4x4_macropad_default.uf2 to the RPI-RP2 drive
3. Done!

Default Layout

┌───┬───┬───┬───┐
│ 7 │ 8 │ 9 │ / │
├───┼───┼───┼───┤
│ 4 │ 5 │ 6 │ * │
├───┼───┼───┼───┤
│ 1 │ 2 │ 3 │ - │
├───┼───┼───┼───┤
│ 0 │ . │Ent│ + │
└───┴───┴───┴───┘

Encoder: Volume up/down

Project Files

• firmware/ - Ready-to-flash .uf2 files
• qmk-config/ - QMK keyboard definition (copy to your QMK install)
• hardware/ - Handwiring guide, BOM, and assembly instructions
• case/ - 3D printable case files
  • case.3mf - 3mf file for main case
  • case.3fd - fusion design file
  • stl/ - STL files for printing
    • Top.stl - Top case part
    • Bottom.stl - Bottom case part
• images/ - Assembly photos and reference images
  • top_view.jpg - Completed macropad from above
  • side_view.jpg - Side profile view
  • rows.jpg - Initial row wiring
  • rows+diodes.jpg - Rows with diodes installed
  • rows+columns.jpg - Complete switch matrix
  • full_wired_on_pi_pico.jpg - Final assembly with controller

Building Your Own

1. Print Required Parts

• Print case.3mf (main case)
• Print MX encoder adapter from Thingiverse Thing:3770166
• Settings: 0.2mm layer height, 20% infill, PLA or PETG

2. Gather Components

See hardware/README.md for the full Bill of Materials.

3. Handwire Assembly

Follow the detailed guide in hardware/assembly.md to:

• Wire the switch matrix
• Connect the Raspberry Pi Pico
• Install the encoder with MX adapter

4. Flash Firmware

Use the Quick Start guide above.

Customizing

Copy qmk-config/jacco_4x4_macropad/ to ~/qmk_firmware/keyboards/ then:

# Edit keymap
nano ~/qmk_firmware/keyboards/jacco_4x4_macropad/keymaps/default/keymap.c

# Edit keyboard.json if needed
nano ~/qmk_firmware/keyboards/jacco_4x4_macropad/keyboard.json

# Compile and flash
qmk flash -kb jacco_4x4_macropad -km default

See QMK docs for more info.

License

Open source hardware and software. See individual files for specific licenses.