Raspberry GrovePi+ with Co2 in nodejs

co2_read_value.js

const struct = require('python-struct');
var serialport = require('serialport');
var SerialPort = serialport;

var port = new SerialPort('/dev/ttyAMA0', {
  baudRate: 9600
});

port.on('open', function () {
  console.log('Port geöffnet /dev/ttyAMA0 @ 9600 bds');
});

setInterval(function () {
  port.write(hex());
}, 1000);

port.on('data', function (byte) {
  var high_level = byte[2];
  var low_level = byte[3];
  var temp = byte[4] - 40; //falsch??? ewig 27C???
  var conc = high_level * 256 + low_level;

  if (!isNaN(temp)) {
    console.log("Temp :", temp);
    console.log("Co2 :", conc);
  }
});


//https://stackoverflow.com/questions/37545844/send-byte-0xff-with-node-js-through-serialport
//Python: "\xff\x01\x86\x00\x00\x00\x00\x00\x79";
function hex() {
  var arr = [];
  arr.push(255);
  arr.push(1);
  arr.push(134);
  arr.push(0);
  arr.push(0);
  arr.push(0);
  arr.push(0);
  arr.push(0);
  arr.push(121);
  return new Buffer(arr);
}

function pack(bytes) {
  var chars = [];
  for (var i = 0, n = bytes.length; i < n;) {
    chars.push(((bytes[i++] & 0xff) << 8) | (bytes[i++] & 0xff));
  }
  return String.fromCharCode.apply(null, chars);
}

Zeile 20: vielleicht ist Taupunkt-Temperatur gemeint, also nicht Lufttemperatur, sondern Temperatur, wo es Wasser in der Luft hat? Oder so etwas? Muss die Spec lesen, gibst du mir Link?