The BM71 is a Bluetooth 5 Module that supports Bluetooth Low Energy (BLE). 

The BM71 uses a UART (or USART) to receive commands from the host microcontroller and send events back over the same interface. 

A typical interface of BM71 to a Microchip microcontroller is provided in the following diagram:

BM71 to MCU Interface

An example demonstration application using this library to interface with the BM71 for BLE functionality is ble_comm, which is used to send a string of characters to a smartphone when the push button is pressed on a development board, and to receive a string of characters from the smartphone causing one of the LEDs to turn on and off, both using the "Transparent Service" feature of the BM71.