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Connect an Arduino to a $7 Bluetooth Serial Module

Make your Arduino communicate with any Bluetooth-enabled device.

Connect an Arduino to a $7 Bluetooth Serial Module

The Arduino microcontroller board is a fantastic starting point for electronic and physical computing projects. As the standard Arduino board does not offer any wireless connection, such as WLAN or Bluetooth, this project shows how to easily connect a $7 Bluetooth serial module to your Arduino. The Bluetooth serial module enables your microcontroller board to communicate with every Bluetooth-equipped device, such as laptops, tablet PCs or smartphones.


Step #1:

Connect an Arduino to a $7 Bluetooth Serial Module

The image shows a $7 Bluetooth serial module that you can readily find on eBay. It offers 4 pins (5V, Ground, RX and TX), that you have to connect with the right pins on your Arduino Uno board. No additional electronic parts are necessary.

Step #2:

Connect an Arduino to a $7 Bluetooth Serial Module

You will need to identify the 5V and Ground pins on your Arduino in order to provide the power source for activating your Bluetooth serial module. Connect the Bluetooth module’s RX pin to the Arduino’s TX pin. Connect the Bluetooth module’s TX pin to the Arduino’s RX pin.

Step #3:

  • After connecting the Bluetooth serial module to your Arduino you are able to pair the Bluetooth module with any Bluetooth-enabled device. Use ’1234′ as the pairing key.
  • There is no additional library necessary for communication. The Bluetooth module replaces a normal serial cable on RX and TX.
  • The Arduino code for writing to the Bluetooth serial module is quite simple: void setup() { Serial.begin(9600); } void loop() { Serial.println("test"); delay(1000); }
  • For receiving the output on your PC just open a terminal program, or Putty, and connect to the COM port of your Bluetooth Serial profile (e.g. COM3 on my PC).


  1. wolfgang says:

    no specific library is needed, it’s normal serial Arduino communication. i added this code to the guide.
    To receive the Arduino output, just open a terminal program and connect to your Bluetooth serial profiles com port (e.g. COM3).

  2. komfushee says:

    I’ve followed your tutorial, but when I try to open the terminal on windows, I get the error “Unable to open connection to COM3 – Unable to open serial port”, the serial connection is on the COM3 when I get the properties of the connection in windows, the speed is set to 9600 on both arduino and windows, but it does not work, any idea why it does that ?

  3. Otto says:

    How do you know the pairing key and how can you change it?
    Also, your code is just writing to the serial monitor, it’s not using the bluetooth at all. Do you have a code that show the bluetooth working?

  4. Mumble says:

    what else can you do with this bluetooth serial module

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  6. Gary says:

    It should also be noted that in order for this to work, the RX and TX wires going between the Arduino and the Bluetooth module should not be connected until the sketch is finished uploading.

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