n 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 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
AndruDroid
Figure 5: ArdruDroid by TechBitar
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 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.