Milesight AT101: LoRaWAN GPS & Wi-Fi Asset Tracker

function decodeUplink(input) {
  var bytes = input.bytes;
  var data = {};

  for (var i = 0; i < bytes.length; ) {
    var channel = bytes[i++];
    var type = bytes[i++];

    if (channel === 0x01 && type === 0x75) {            // battery (%)
      data.battery = bytes[i]; i += 1;
    } else if (channel === 0x03 && type === 0x67) {     // temperature (°C)
      data.temperature = readInt16LE(bytes, i) / 10; i += 2;
    } else if (channel === 0x83 && type === 0x67) {     // temperature + alarm flag
      data.temperature = readInt16LE(bytes, i) / 10;
      data.temperature_alarm = bytes[i + 2] === 1 ? "abnormal" : "normal";
      i += 3;
    } else if ((channel === 0x04 || channel === 0x84) && type === 0x88) { // location
      data.latitude = readInt32LE(bytes, i) / 1000000;
      data.longitude = readInt32LE(bytes, i + 4) / 1000000;
      var status = bytes[i + 8];
      data.motion_status = MOTION[status & 0x0f];
      data.geofence_status = GEOFENCE[status >> 4];
      i += 9;
    } else if (channel === 0x05 && type === 0x00) {     // device position
      data.position = bytes[i] === 1 ? "tilt" : "normal"; i += 1;
    } else if (channel === 0x07 && type === 0x00) {     // tamper status
      data.tamper_status = bytes[i] === 1 ? "uninstall" : "install"; i += 1;
    } else if (channel === 0x06 && type === 0xd9) {     // Wi-Fi scan result
      var wifi = {
        mac: readMAC(bytes, i + 1),
        rssi: readInt8(bytes[i + 7])
      };
      data.wifi = data.wifi || [];
      if (wifi.mac !== "ff:ff:ff:ff:ff:ff") data.wifi.push(wifi);
      i += 9;
    } else {
      break;                                            // unknown channel
    }
  }
  return { data: data };
}

var MOTION = { 0: "unknown", 1: "start", 2: "moving", 3: "stop" };
var GEOFENCE = { 0: "inside", 1: "outside", 2: "unset", 3: "unknown" };

function readInt8(b) { return b > 0x7f ? b - 0x100 : b; }
function readInt16LE(b, i) {
  var v = (b[i + 1] << 8) | b[i];
  return v > 0x7fff ? v - 0x10000 : v;
}
function readUInt32LE(b, i) {
  return ((b[i + 3] << 24) | (b[i + 2] << 16) | (b[i + 1] << 8) | b[i]) >>> 0;
}
function readInt32LE(b, i) {
  var v = readUInt32LE(b, i);
  return v > 0x7fffffff ? v - 0x100000000 : v;
}
function readMAC(b, i) {
  var out = [];
  for (var k = 0; k < 6; k++) out.push(("0" + (b[i + k] & 0xff).toString(16)).slice(-2));
  return out.join(":");
}