Wireless 70% Keyboard: PCB & Firmware Documentation

_Made by: @Programer6

July 10, 2024 - Initial Schematic & Matrix Layout (4 hours)

Kicked off the project today by designing the core schematic in KiCad. The main focus was creating the key matrix for a custom 70% layout. I settled on a 6-row by 14-column matrix, which accommodates a function row, number row, three alpha rows, and a bottom modifier row.

Ensured, each switch (MX1 through MX74) is paired with a diode (e.g., D1, D2).

July 11, 2024 - Microcontroller Selection & I/O Expansion (3 hours)

Today was all about selecting the core components and figuring out the GPIO strategy. For a wireless build, the nice!nano was the obvious choice due to its built-in wireless capabilities and excellent ZMK firmware support.

However, the 20 pins required for the 6x14 matrix would stretch the nice!nano's available GPIOs to the limit, making PCB routing a nightmare. To solve this, I added an MCP23017 I/O expander.

July 12, 2024 - cad (5 hours)

After finalizing the PCB, I exported the 3D model from KiCad and imported it into Fusion 360. I designed a simple and functional two-part case: a main body that holds the PCB and a top frame that acts as a switch plate and bezel.

July 29, 2024 - ZMK Repository Setup (2.5 hours)

I followed the ZMK documentation to create a new zmk-config repository. This process involved running a setup script that creates the basic folder structure and configuration files. I named the new board 70keyboard and set up the initial build.yaml file to target the nice!nano_v2 board.

July 30, 2024 - Writing the Device Tree Overlay (5.5 hours)

I mapped the 14 matrix columns directly to the nice!nano's pins and assigned the 6 rows to the MCP23017 I/O expander, configuring the I2C bus to let them communicate. And of course, I defined the two pins for the rotary encoder to complete the hardware setup.

July 31, 2024 - Creating the Keymap (4 hours)

I built the keymap by laying out all the standard keys, creating an Fn layer for Bluetooth and bootloader shortcuts, and configuring the encoder to control volume with a push-to-mute function.