There are a few things to consider when buying a Bluetooth interface.

  • A HC-06 can only operate as a slave. A HC-05 (which is exactly the same hardware, but different firmware loaded) can be a slave and a master.
  • Watch out if you buy these, for normal 2.54 mm spaced boards, you need a little host board. Read carefully when ordering, ou want a module PLUS host boards, not just one or the other.
HC-05/06 with host board
Only HC-05/06.
Only host board

How to make a HC-05 a slave module

  • Connect to the module, either from an Arduino or a UsbToSerial Adapter, ensure 38400 bps
  • Boot while pin 34 of the module is connected to 3.3V. This will put it in command (AT) mode
  • AT+ORGL (answer should be OK) set to factory default
  • AT+NAME=1234 (OK) set the BT name of the device (1234 is an example)
  • AT+RMAAD (OK) remove all previous pairings
  • AT+PSWD=1234 (OK) set the BT password (1234 is an example)
  • AT+ROLE=0 (OK) set the module in slave mode
  • AT+INIT connect with this profile

Now reboot with pin 34 connected to ground.

Placeholder how to make a HC-06 a slave module