How to identify the Master module and slave module? 1. there is a white spot on the main chip of master module while there is none on the slave module 2. Master module can only communicate with slave module can. Slave module can communicate with master module and PC Bluetooth adapters PDA and Bluetooth cell phones; Bluetooth-pin interface: (PIN to PIN space: standard 2.54mm); Compatible w/ 3~5V microcontroller; 1. STATUS: Bluetooth status output sustained high level indicates that the data link has been established. Microcontroller IO port can be connected to query the status of Bluetooth ; It is not essential to connected STATUS 2. VCC: power connector 5V. (Must be connected) 3. GND: negative power (Must be connected) 4.TXD: data output interface you need to connect the microcontroller data input interface; Generally the name of MCU IO is RX or RXD. 5. RXD: data reception interface you need to connect the microcontroller data transmission interface; Generally the name single-chip IO is TX or TXD. 6. MCLR: Clear the pairing function of main module; Generally connect to one of microcontroller IO; Microcontroller outputs a 500ms low level then output high level to clear the Bluetooth host pairing information