Basic analog read, using Firmata

ana_read.js

var firmata = require('firmata');

var analogPin = 3;

var board = new firmata.Board('/dev/tty.usbmodemfd121', function(err) {
  if (err){
    console.log(err);
    process.exit(1);
  }
  
  setInterval(function(){
    board.analogRead(analogPin, function(val){
      console.log(val);
    });
  }, 500);
});