buzzer.js

'use strict';

const async = require('async');
const gpio = require('rpi-gpio');
const BUZZER_PIN = 5;
const TIME_ON = 150;
const TIME_OFF = 900;
const BUZZ_TIME = 20;

gpio.setMode(gpio.MODE_BCM);
gpio.setup(BUZZER_PIN, gpio.DIR_LOW, write);

function makeSound(cb) {
  setTimeout(() => {
    gpio.write(BUZZER_PIN, true, cb);
  }, TIME_OFF);
}

function muteSound(cb) {
  setTimeout(() => {
    gpio.write(BUZZER_PIN, false, cb);
  }, TIME_ON);
}

function highAndLow(callback) {
  makeSound((err) => {
    muteSound((err) => {
      callback(err);
    });
  });
}

function write() {
  let count = 0;
  async.whilst(
    () => { return count < BUZZ_TIME; },
    (cb) => { count++; highAndLow(cb); },
    function (err, n) {
      console.log(err, n);
    }
  );
}

process.on('SIGINT', function () {
  console.log("Caught interrupt signal");
  muteSound(() => {
    process.exit();
  });
});