Arduino BLE keyboard

This project was born out of curiosity and a certain aversion to buying a Bluetooth keyboard that will sit and collect dust most of the time.

It was also a project to explore how does Swift UI fare on Mac OS (spoiler: quite good, but not without its' problems) and to to work with custom-defined BLE interaction protocol.

Components of the project

• Client for macOS that sends keypresses to Arduino Nano 33 BLE
• Firmware for Arduino Nano 33 BLE that takes the data sent by client and emulates keypresses as a Human Interface Device

BLE interactions

BLE specifications in this firmware are pretty simple:

• Device advertises itself with the name Virtual Keyboard
• Service 98AD is advertised - let's refer to it as keyboard service
• Characteristic 98AF is a part of keyboard service. It can only be written to without confirmation. Let's refer to it as RX characteristic.
• On every write to RX characteristic, a keypress will be generated based on the data written.

Data format for RX characteristic

• Size: 32 bits
• First 16 bits are for HID key code (the key itself) as an unsigned integer
• Second 16 bits are for HID key modifier (Shift, Ctrl, etc.) as an unsigned integer
• Integers should be big-endian

It's not intended to be used as a keyboard replacement for something serious - if you need a keyboard, just go and buy one. This is mostly for fun and to see what interesting things could be squeezed out of Arduino.

Known problems

• Sending input while screen is locked will lock up the device, leading to BLE connection loss sometimes.