qmk_firmware/docs/feature_bluetooth.md

Bluetooth

Bluetooth Known Supported Hardware

Currently Bluetooth support is limited to AVR based chips. For Bluetooth 2.1, QMK has support for RN-42 modules and the Bluefruit EZ-Key, the latter of which is not produced anymore. For more recent BLE protocols, currently only the Adafruit Bluefruit SPI Friend is directly supported. BLE is needed to connect to iOS devices. Note iOS does not support mouse input.

Board	Bluetooth Protocol	Connection Type	rules.mk	Bluetooth Chip
Adafruit EZ-Key HID	Bluetooth Classic	UART	BLUETOOTH = AdafruitEZKey
Roving Networks RN-42 (Sparkfun Bluesmirf)	Bluetooth Classic	UART	BLUETOOTH = RN42	RN-42
Bluefruit LE SPI Friend	Bluetooth Low Energy	SPI	BLUETOOTH = AdafruitBLE	nRF51822

Not Supported Yet but possible:

• Bluefruit LE UART Friend. Possible tmk implementation found in
• HC-05 boards flashed with RN-42 firmware. They apparently both use the CSR BC417 Chip. Flashing it with RN-42 firmware gives it HID capability.
• Sparkfun Bluetooth Mate
• HM-13 based boards

Adafruit BLE SPI Friend

Currently The only bluetooth chipset supported by QMK is the Adafruit Bluefruit SPI Friend. It's a Nordic nRF5182 based chip running Adafruit's custom firmware. Data is transmitted via Adafruit's SDEP over Hardware SPI. The Feather 32u4 Bluefruit LE is supported as it's an AVR mcu connected via SPI to the Nordic BLE chip with Adafruit firmware. If Building a custom board with the SPI friend it would be easiest to just use the pin selection that the 32u4 feather uses but you can change the pins in the config.h options with the following defines:

• #define AdafruitBleResetPin D4
• #define AdafruitBleCSPin B4
• #define AdafruitBleIRQPin E6

A Bluefruit UART friend can be converted to an SPI friend, however this requires some reflashing and soldering directly to the MDBT40 chip.

Adafruit EZ-Key hid

This requires some hardware changes, but can be enabled via the Makefile. The firmware will still output characters via USB, so be aware of this when charging via a computer. It would make sense to have a switch on the Bluefruit to turn it off at will.

Bluetooth Rules.mk Options

Use only one of these

• BLUETOOTH_ENABLE = yes (Legacy Option)
• BLUETOOTH = RN42
• BLUETOOTH = AdafruitEZKey
• BLUETOOTH = AdafruitBLE

Bluetooth Keycodes

This is used when multiple keyboard outputs can be selected. Currently this only allows for switching between USB and Bluetooth on keyboards that support both.

Name	Description
OUT_AUTO	Automatically switch between USB and Bluetooth
OUT_USB	USB only
OUT_BT	Bluetooth only