Code for Arduino and Bluetooth module. Copyright © 2014 by K-ways.

bluetoothMaster.ino

#include <SoftwareSerial.h>
SoftwareSerial BT(11, 12);   // RX & TX

char val;
boolean state2 = 0;

void setup()
{
  pinMode(13, OUTPUT);
  digitalWrite(13, 1);
  pinMode(2, INPUT);
  digitalWrite(2, 1);
  BT.begin(9600);
}

void loop()
{
  val = digitalRead(2);
  if(val == 0 && state2 == 0)
  {
    BT.write('2');
    //BT.print('2');
    state2 = 1;
  }

  else if(val == 1 && state2 == 1)
  {
    BT.write('0');	//不可write(0)
    state2 = 0;
  }
}

bluetoothSlave.ino

#include <SoftwareSerial.h>
SoftwareSerial BT(11, 12);   // RX & TX

char val;

void setup()
{
  BT.begin(9600);
  pinMode(13, OUTPUT);
  digitalWrite(13, 0);
}

void loop()
{
  if (BT.available())
  {
	val = BT.read();
	if (val == '2')
	    digitalWrite(13, 1);
	else
	    digitalWrite(13, 0);
  }
  
}

setupAT.ino

#include <SoftwareSerial.h>
SoftwareSerial BT(11, 12);   // RX & TX
 
void setup()
{
  BT.begin(38400);
  Serial.begin(9600);
  Serial.println("Enter commands:");
}
 
void loop()
{
  if (BT.available())
  {
    char data = BT.read();
    Serial.print(data);
  }
  if (Serial.available())
    BT.write(Serial.read());
}