Budget Wireless Corne Keyboard Build

A DIY wireless split keyboard based on the Corne layout, built for approximately $25 USD. This project uses a ProMicro clone with nrf52840 chip, making it a cost-effective alternative to traditional wireless split keyboard builds.

Features

• Fully wireless using Bluetooth
• Split ergonomic design (Corne layout)
• Low profile design for portability
• Battery-powered with power switch
• ZMK firmware
• Estimated battery life: 1+ month

Bill of Materials

| Component | Quantity | Cost (USD) | Link | |-----------|----------|------------|------| | Controller boards (ProMicro nrf52840) | 2 | 6.82 | AliExpress | | Batteries | 2 | 4.20 | AliExpress | | Mechanical Switches | 50 | 7.47 | AliExpress | | Keycaps | Set | 3.79 | Option 1 / Option 2 | | Diodes (1N4148) | 100 | 0.85 | AliExpress | | Slide Switches | 2 | 0.11 | | | 3D Printed Parts | Set | 1.80 | Files provided |

Total Cost: $25.04 (excluding wires and screws)

Current Keymap

Build Instructions

Prerequisites

• Basic soldering skills
• Access to a 3D printer
• Basic understanding of keyboard firmware

Case Assembly

1. Print the case files (STL files provided in 3DFiles directory)
2. Note: You may need to adjust the:
   • Battery compartment size
   • Slide switch holes

Wiring

1. Wire switches in a matrix configuration
2. Connect diodes:
   • Direction matters (black line indicates cathode)
   • Use diode legs for the rows
   • Use separate wires for columns
3. Keep wiring clear of screw holes
4. Connect the battery:
   • GND to GND pin
   • Positive to one of the side legs on the slide switch
   • Middle pin of the slide switch to the RAW pin

Pin Connections for Rows and Columns

The matrix configuration uses GPIO pins on the nRF52840 Pro Micro clone. Below are the connections:

How Rows and Columns Are Numbered

• Rows: Rows are always numbered from top to bottom on both halves.
• Columns: Columns are always numbered from left to right (as viewed from the back of the plate (where the wiring is done)).

⚠️ Note: If you accidentally solder the rows or columns to the wrong pins, you do not need to desolder. The mappings can be fixed in the firmware configuration files:

• corne.dtsi: Defines rows for both halves.
• corne_left.overlay: Defines columns for the left half.
• corne_right.overlay: Defines columns for the right half.

Left Half Pin Assignments

• Rows (Connected to row-gpios):
  • Row 0: Pin 21
  • Row 1: Pin 20
  • Row 2: Pin 19
  • Row 3: Pin 18
• Columns (Connected to col-gpios):
  • Column 0: Pin 2
  • Column 1: Pin 7
  • Column 2: Pin 6
  • Column 3: Pin 5
  • Column 4: Pin 4
  • Column 5: Pin 3

Right Half Pin Assignments

• Rows (row-gpios):
  • Row 0: Pin 21
  • Row 1: Pin 20
  • Row 2: Pin 19
  • Row 3: Pin 18
• Columns (col-gpios):
  • Column 0: Pin 3
  • Column 1: Pin 4
  • Column 2: Pin 5
  • Column 3: Pin 6
  • Column 4: Pin 7
  • Column 5: Pin 2

Firmware Setup

This keyboard uses ZMK firmware. The left half acts as the main controller that connects to your device.

To flash the firmware:

1. Double press the reset button
2. Board will appear as mass storage device
3. Flash the appropriate firmware file

If you forgot the keyboard from your device and can't reconnect:

1. Flash the settings_reset-nice_nano_v2-zmk.uf2 file
2. Reflash the regular firmware
3. Pair

Repository Structure

├── .github/workflows/
│   └── build.yml
├── 3DFiles/
│   ├── STEP/
│   │   └── CorneSTEP.step
│   ├── STL/
│   │   ├── Case_Left.stl
│   │   ├── Case_Right.stl
│   │   └── PlateCorne.stl
├── config/
│   ├── boards/shields/corne/
│   │   ├── corne_left.conf
│   │   ├── corne_left.overlay
│   │   ├── corne_right.conf
│   │   ├── corne_right.overlay
│   │   ├── corne.conf
│   │   ├── corne.dtsi
│   │   ├── Kconfig.defconfig
│   │   └── Kconfig.shield
│   ├── corne.keymap
│   └── west.yml
├── firmware/
│   ├── corne_left-nice_nano_v2-zmk.uf2
│   ├── corne_right-nice_nano_v2-zmk.uf2
│   └── settings_reset-nice_nano_v2-zmk.uf2
└── zephyr/
    ├── module.yml
    └── build.yaml

Known Issues

• Left side case may have warping issues if battery swells
• Slide switch holes may need adjustment based on your components

Final result