Bluetooth projects in Harmony consist of an application, plus associated drivers and peripheral libraries (PLIBs). Projects using Harmony Bluetooth typically connect to either Bluetooth module external to the MCU, using a UART interface for control.

The block diagram above depicts a generic Bluetooth BLE application that sends and receives a string of characters to and from a smartphone. 

The application interfaces directly with a Bluetooth Module Driver and a Timer. The Bluetooth Module Driver in turn interfaces with a USART Driver so it can send commands and receives status from the external Bluetooth module. GPIO pins may also be connected to the Bluetooth module.