Milesight WS302: LoRaWAN Sound Level Sensor

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

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

    // Device info on join / power-on (IPSO, versions, SN, class)
    if (channel === 0xff) {
      if (type === 0x01) { i += 1; }                       // protocol version
      else if (type === 0x09 || type === 0x0a) { i += 2; } // hardware / firmware version
      else if (type === 0xff) { i += 2; }                  // TSL version
      else if (type === 0x16) { i += 8; }                  // serial number
      else if (type === 0x0f || type === 0x0b) { i += 1; } // LoRaWAN class / device status
      else if (type === 0xfe) { i += 1; }                  // reset event
      else { break; }
    } else if (channel === 0x01 && type === 0x75) {        // battery (%)
      data.battery = bytes[i]; i += 1;
    } else if (channel === 0x05 && type === 0x5b) {        // sound level (dB)
      var weight = bytes[i];
      var freq = ["Z", "A", "C"][weight & 0x03];           // frequency weighting
      var time = ["I", "F", "S"][(weight >> 2) & 0x03];    // time weighting
      data["L" + freq + time]         = readUInt16LE(bytes, i + 1) / 10; // instantaneous
      data["L" + freq + "eq"]         = readUInt16LE(bytes, i + 3) / 10; // equivalent
      data["L" + freq + time + "max"] = readUInt16LE(bytes, i + 5) / 10; // maximum
      i += 7;
    } else {
      break;
    }
  }
  return { data: data };
}

function readUInt16LE(b, i) {
  return (b[i + 1] << 8) | b[i];
}