Currently Bluetooth support is limited to AVR based chips. For Bluetooth 2.1, QMK has support for RN-42 modules. 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.
Roving Networks RN-42 (Sparkfun Bluesmirf)
Bluetooth Low Energy
Not Supported Yet but possible:
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
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.
The currently supported Bluetooth chipsets do not support N-Key Rollover (NKRO), so
rules.mk must contain
NKRO_ENABLE = no.
Use only one of these to enable Bluetooth:
BLUETOOTH_ENABLE = yes (Legacy Option)
BLUETOOTH = RN42
BLUETOOTH = AdafruitBLE
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.
Automatically switch between USB and Bluetooth