Arduino Smoke Alarm Receiver Code

// Arduino Smoke Alarm Receiver Code
// by Ido Gendel
#include <VirtualWire.h>

#define SPEAKER_PIN 8
#define DATA_PIN 2

// Sound the alarm - 3 tones of 1 sec
// with 1 sec delay between them
void alarm() {

  for (byte j = 0; j < 3; j++) {
    tone(SPEAKER_PIN, 3150);
    delay(1000);
    noTone(SPEAKER_PIN);
    delay(1000);
  }

}

void setup() {

 // Prepare VirtualWire for receiving
 vw_set_rx_pin(DATA_PIN);
 vw_setup(1200); // Bits per sec
 vw_rx_start();

}

void loop() {

  uint8_t buf[2];
  uint8_t buflen = 2;

  // Wait for message
  vw_wait_rx();

  // Is it a complete "message"?
  if (vw_get_message(buf, &buflen)) {

    // is it the activation code?
    // This check is hard-coded, should be written more generally
    // for serious applications
    if ((buf[0] == 170) && (buf[1] == 205)) alarm();

  }

}