Arduino + JY-MCU Module + Bluetooth Android Application

This is a simple instructable how to create a working link between Android and Arduino via JY-MCU Module. By the end of this instructable you will be able to control LED with Android Application.

Step 1: Materials

You will need:

Arduino (any version is good, I used nano).
JY-MCU Module (Purchased on dx.com).
An Android Phone with BlueControl application installed.

Step 2: Connect Arduino to JY-MCU

You will need voltage divider to connect JY-MCU RX to Arduino TX. I used a 3 x 10 KOhm Resistors. You can use any combination of resistors as long as you get 3.3 Volts going to RX of JY-MCU Module.

Connect Ground of JY-MCU to Ground of Arduino.
Connect 5V output of Arduino to Vcc of JY-MCU.
Connect JY-MCU TX to Arduino RX.
Connect via voltage divider JY-MCU RX to Arduino TX.
Connect ground of voltage divider to ground of Arduino.
- Not using voltage divider will result in damaging the module.

Step 3: Upload the Following Sketch to Arduino

/* Turn an LED on/off based on a command send via BlueTooth

**
** Credit: The following example was used as a reference
** Rui Santos: http://randomnerdtutorials.wordpress.com
*/

int ledPin = 13;  // use the built in LED on pin 13 of the Uno
int state = 0;
int flag = 0;        // make sure that you return the state only once

void setup() {
    // sets the pins as outputs:
    pinMode(ledPin, OUTPUT);
    digitalWrite(ledPin, LOW);

    Serial.begin(9600); // Default connection rate for my BT module
}

void loop() {
    //if some data is sent, read it and save it in the state variable
    if(Serial.available() > 0){
      state = Serial.read();
      flag=0;
    }
    // if the state is 0 the led will turn off
    if (state == '0') {
        digitalWrite(ledPin, LOW);
        if(flag == 0){
          Serial.println("LED: off");
          flag = 1;
        }
    }
    // if the state is 1 the led will turn on
    else if (state == '1') {
        digitalWrite(ledPin, HIGH);
        if(flag == 0){
          Serial.println("LED: on");
          flag = 1;
        }
    }
}