Sketch that tests the functionality of the BluetoothWrapper Android library. It demonstrates a connection between an Arduino board and a Bluetooth module (currently HC-05).

BluetoothWrapperArduino.ino

/**
   Sketch that tests the functionality of the BluetoothWrapper Android
   library available here: https://github.com/GeorgiosGoniotakis/BluetoothWrapper

   It demonstrates a connection between an Arduino board and a
   Bluetooth module (currently HC-05).

   author: Georgios Goniotakis
   date: 07 Oct 2017
   version: 1.0.0
*/
#include <SoftwareSerial.h>

#define TXD 2 // RXD Pin of the Bluetooth Module
#define RXD 3 // TXD Pin of the Bluetooth Module
#define LED_PIN 13 // Arduino LED pin
#define UPDATE_INTERVAL 1000 // Time interval for sending a serial message

SoftwareSerial mySerial(RXD, TXD); // Initialize a new serial channel with the bluetooth module

unsigned long previous = 0;

void setup() {
  mySerial.setTimeout(50);
  mySerial.begin(9600); // Initialize the serial port
  pinMode(LED_PIN, OUTPUT); // Set the LED pin as output
}

void loop() {

  unsigned long current = millis();

  /* Transmitting a message to serial output */
  if (current - previous >= UPDATE_INTERVAL) {
    mySerial.println("INPUT STRING");
    previous = current;
  }

  /* Reading a string from serial input */
  if (mySerial.available() > 0) {

    String input = mySerial.readString();

    /* If incoming message equalt to "OPEN" then blink LED 
       Please do not use delay() in your code, this is just
       for demonstration purposes
    */
    if (input.equals("OPEN")) {
      digitalWrite(LED_PIN, HIGH);
      delay(500);
      digitalWrite(LED_PIN, LOW);
      delay(500);
    }
  }
}