Wireless Keyboard Project: Hardware

These are Eagle design files for PCBs used in my wireless keyboard project.

Engineering Overview

Each keyboard section runs a Nordic nRF51822 in the Waveshare core51822-b package, powered by a lithium ion battery.

Instead of using a traditional matrix that requires constant scanning (and thereby constant power usage), each key is connected to its own dedicated pin. This way, the chip can enter sleep until interrupted by a key press.

When a key press occurs, it is first debounced to prevent the mechanical switch from generating extra key presses. After that, the pressed keys are collected and transmitted through the Gazell protocol to the receiver.

The receiver transforms the pressed keys into a matrix and passes that off the the ATmega32U4 Pro Micro, which runs QMK firmware. The Pro Micro sends the signal over USB to the computer as input.

Keyboard Layout

http://www.keyboard-layout-editor.com/#/gists/4d522280e8e3315902466de2c982f663

Folder Structure

• 3d contains SketchUp renderings of what the final product could look like. These are not dimensionally accurate.
• fab contains design rules and CAM settings for DirtyPCBs and OSH Park
• lib contains device libraries that are used by the receiver and keyboard projects.

PCB Fab Specifications

• FR4 fiberglass
• 2 layer
• 1.6mm thickness

Keyboard PCBs

A single, reversible board is used for each keyboard half. The top of the board is used for the left half, and the bottom for the right half: