What Is Master Slave Communication

- Jun 24, 2019-

For Bluetooth Data Module applications, devices usually work in Master Mode or Slave Mode


1.     What’s the Master Mode and the Slave Mode?

Master Mode: Bluetooth device in Master Mode, it could scan other Bluetooth devices which are broadcasting in slave Mode. Normally, Feasycom Bluetooth Master Module could connect with 10 Bluetooth slave devices at the same time. Bluetooth Master devices are also named as scanners or Initiators.

Slave Mode: Bluetooth device in Slave Mode, will not search for other Bluetooth devices. It can only be connected by Bluetooth devices in Master Mode.


When the Master and Slave devices are connected with each other, they could send and receive data from each other via TXD, RXD ports.

   2.SPP Master-Slave

l  One of the standard firmwares of the module simultaneously supports SPP master and SPP slave features, when the user use the AT commands for the SPP master feature, the module will act as master role, otherwise, it acts as slave role.

l  The list of AT commands for the SPP master feature:




Scan nearby devices


Establish SPP connection


Read SPP state

Only available in AT-command mode


Release SPP connection


Send data via SPP

Note: for more information about these commands, please refer to FSC-BT8XX Programming User Guide   V3.2(Dual-Mode Data Transiver)

l  Typical AT-Command Mode SPP Master Interaction:

For more details feel free to contact feasycom team :sales@feasycom.com