How To Change An HC-05 Bluetooth Transceiver From A Slave To A Master
What’s In This Page
A step by step guide for changing the mode of an HC-05 so that you can use it to send audio from an MP3 player to other devices such as a Bluetooth speaker an android phone and ear phones, to name a few.
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Why This Procedure
The default configuration for an HC-05 is the slave mode. That means that it receives data.
In the master mode, it sends data to other Bluetooth devices.
Procedure
To change the HC-05 Bluetooth module from slave mode to master mode, you need to enter AT command mode on the HC-05 and issue specific AT commands.
Equipment Needed
HC-05 Bluetooth module
Arduino Nano, Uno or Arduino Mini Pro
Jumper wires
Arduino IDE installed on a computer
Step By Step Guide
Make the following connections:
VCC on the HC-05 to Arduino 5V
GND on the HC-05 to Arduino GND
TX on the HC-05 to Arduino RX (Pin 0)
RX on the HC-05 to Arduino TX (Pin 1)
Key/EN (sometimes labeled as AT) on the HC-05 to Arduino 3.3V
Enter AT Command Mode:
To enter AT command mode, the HC-05 needs to be powered on with the Key/EN pin held high.
The Key/EN pin is connected to the Arduino 3.3V.
Connect the Arduino to your computer.
The LED on the HC-05 should blink slowly (about 2 seconds interval), indicating it is in AT command mode.
Open The Serial Monitor On YourComputer As Follows
Upload a new sketch with empty `setup()` and `loop()` functions to the Arduino board.
In Tools, open the Serial Monitor
Set the baud rate to 38400 (the default for AT mode).
Ensure both “Both NL & CR” or similar option is selected in the line ending dropdown in the Serial Monitor.
Send AT Commands
In the Serial Monitor, type `AT` and press enter.
The module should respond with `OK`.
Type AT+ROLE=1
You should get a response `OK`.
The HC-05 is now in master mode.
Verify The Mode Change
Type in the Serial Monitor AT+ROLE?
The response should be `+ROLE:1`, indicating the module is now in master mode.
Sequence Summary
ConnectHC-05 to the Arduino board
Connect the Arduino to your computer
The LED should blink slowly
Serial Monitor Commands
Type: `AT` and press Enter. Response: `OK`
Type: `AT+ROLE=1` and press Enter. Response: `OK`
Type: `AT+ROLE?` and press Enter. Response: `+ROLE:1`
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