Milesight VS135: Ultra ToF LoRaWAN People Counter

function decodeUplink(input) {
  var bytes = input.bytes;
  var data = { lines: {}, regions: {}, dwell: {} };

  // Channel groups (IPSO): each counting line uses a fixed triplet of channels.
  var inChns = [0x03, 0x06, 0x09, 0x0c];
  var outChns = [0x04, 0x07, 0x0a, 0x0d];
  var periodChns = [0x05, 0x08, 0x0b, 0x0e];

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

    // Device info on join / power-on: skip with known lengths.
    if (channel === 0xff) {
      if (type === 0x01) { i += 1; }        // protocol version
      else if (type === 0x09) { i += 2; }   // hardware version
      else if (type === 0x16) { i += 8; }   // serial number
      else if (type === 0x1f) { i += 4; }   // firmware version
      else { break; }                       // downlink-response payloads vary
      continue;
    }

    // Line total IN: UINT32 little-endian.
    if (idx(inChns, channel) >= 0 && type === 0xd2) {
      data.lines["line_" + (idx(inChns, channel) + 1) + "_in"] = readUInt32LE(bytes, i);
      i += 4; continue;
    }
    // Line total OUT: UINT32 little-endian.
    if (idx(outChns, channel) >= 0 && type === 0xd2) {
      data.lines["line_" + (idx(outChns, channel) + 1) + "_out"] = readUInt32LE(bytes, i);
      i += 4; continue;
    }
    // Line period IN/OUT: two UINT16 little-endian values.
    if (idx(periodChns, channel) >= 0 && type === 0xcc) {
      var n = idx(periodChns, channel) + 1;
      data.lines["line_" + n + "_period_in"] = readUInt16LE(bytes, i);
      data.lines["line_" + n + "_period_out"] = readUInt16LE(bytes, i + 2);
      i += 4; continue;
    }
    // Region count: four UINT8 head counts.
    if (channel === 0x0f && type === 0xe3) {
      for (var r = 0; r < 4; r++) { data.regions["region_" + (r + 1)] = bytes[i + r]; }
      i += 4; continue;
    }
    // Region dwell time: region id + avg + max (UINT16 little-endian, seconds).
    if (channel === 0x10 && type === 0xe4) {
      var region = bytes[i];
      data.dwell["region_" + region + "_avg"] = readUInt16LE(bytes, i + 1);
      data.dwell["region_" + region + "_max"] = readUInt16LE(bytes, i + 3);
      i += 5; continue;
    }
    // Occlusion / sensor alarm: node id + alarm type.
    if (channel === 0x50 && type === 0xfc) {
      data.alarm = { node: bytes[i + 1], type: bytes[i + 2] };
      i += 3; continue;
    }

    break; // unknown channel: stop, the mapping is deployment-specific
  }
  return { data: data };
}

function idx(arr, v) {
  for (var k = 0; k < arr.length; k++) { if (arr[k] === v) { return k; } }
  return -1;
}
function readUInt16LE(b, i) {
  return ((b[i + 1] << 8) | b[i]) & 0xffff;
}
function readUInt32LE(b, i) {
  return ((b[i + 3] << 24) | (b[i + 2] << 16) | (b[i + 1] << 8) | b[i]) >>> 0;
}