How to Use HC-05 Bluetooth Module With Arduino

Illustration In the Definition part, we declare the LED variable that accepts 12 (in other words the Digital PIN). And the char input that we will further use for accepting the user's instructions. Until now, we have just declared two variables. Next we have a setup() block where we will initialize a LED and serial communication. So, we have pinMode() and Serial.begin(). In the next loop() block we do all the actual coding. First, we decide whether or not the serial port is available. If yes, then we will do the communication. For that, we have a Serial Method available(). On yes, we proceed and ask for the user's input via the serial port. And, the read() method is there that accepts input from the serial port. Whatever value we get from the serial port we store in the input variable that we defined earlier. And, on the input, it will decide to turn it on or not. See, we haven't written any code for Bluetooth communication. So, that's because Bluetooth communication is implicitly Serial Communication. And in Arduino, what you can do with the Serial Monitor in Arduino is that you can also implement Bluetooth Serial Communication. Before we connect to the Android Phone, install an app that will do the rest of the job. ArdruDroid Note: Play Store link. This App is designed for Arduino Bluetooth Communication. With That SEND button, we can send instructions to the HC-05 module. Whereas, the GET button is used to see what HC-05 is returning as the return value. Since here we have two instructions, 1 (true) to turn on the LED and the other is 0 (false) to turn off the LED. Output

Use the following procedure.

1. Upload the code to the Arduino UNO where we have successfully attached the Bluetooth HC-05 module.
   Note: When uploading the sketch please remove the RX and TX wires from the Arduino UNO. I don't even know why they don't work when they are attached. After successfully uploading, attach RX and TX to the board.
   
   Figure 6: Program
2. After successfully Uploading check whether the Bluetooth module is working or not. (The easiest way is to see if the RED indicator is blinking).
   
   Figure 7: Blinking RED indicator
3. Now, go to the Bluetooth Settings on your phone and pair your phone with the HC-05 Device. The key is 1234.
   
   Figure 8: Bluetooth on
4. After successfully pairing, open the ArduDroid App and connect with the HC-05 module.
   
   Figure 9: ArduDroid App
5. After doing this, now you can send instructions to the HC-05 with your app. So, we are sending 1 as input.
   
   Figure 10: Send instruction to HC-05
   After sending, you see something like this.
   
   Figure 11: After sending
6. And 0 to turn off the LED.
   
   Figure 12: 0 to turn off the LED
   And then:
   
   Figure 13: Turn off the LED