Function to decode Helium's uplink data from RAK7204 device. Data are in LPP Cayenne format (RUI: RAK Unified Interface) and converted to Ubidots JSON format as expected. Inspired from GitHub projet : https://github.com/RAKWireless/RUI_LoRa_node_payload_decoder

RAK7204SensorDataDecoder_for_Ubidots.js

// Function to decode Helium's uplink data from RAK7204 device.
// Data are in LPP Cayenne format (RUI: RAK Unified Interface) and converted to Ubidots JSON format as expected.
// Decoder decodes an array of bytes and uplink_info into an object.
// - port contains the LoRaWAN fPort number
// - bytes is an array of bytes, e.g. [225, 230, 255, 0]
// - uplink_info contains data from the device treated by the Helium router, e.g. { app_eui: <app_eui>, fcnt: <integer>, reported_at: <timestamp> }
// The function must return an object, e.g. { "temperature": { "value": <float>, "timestamp": <timestamp>} }
function Decoder(bytes, port, uplink_info)  {
  var decoded = {};
  var hexString = bin2HexStr(bytes);
  return rakSensorDataDecode(hexString, uplink_info);
}

// convert array of bytes to hex string.
// e.g: 026700f00768750673275a0c650053080201b9
function bin2HexStr(bytesArr) {
  var str = "";
  for (var i = 0; i < bytesArr.length; i++) {
    var tmp = (bytesArr[i] & 0xff).toString(16);
    if (tmp.length == 1) {
      tmp = "0" + tmp;
    }
    str += tmp;
  }
  return str;
}

// convert string to short integer
function parseShort(str, base) {
  var n = parseInt(str, base);
  return (n << 16) >> 16;
}

// convert string to triple bytes integer
function parseTriple(str, base) {
  var n = parseInt(str, base);
  return (n << 8) >> 8;
}

// decode Hex sensor string data to object
function rakSensorDataDecode(hexStr, uplink_info) {
  // Default timestamp
  var timestamp = Date.now();
  if (uplink_info) {
    timestamp = uplink_info.reported_at; // Timestamp reported by the Helium router
  }
  var str = hexStr;
  var data = {};
  var context = {};
  context.uplink_fcnt = uplink_info.fcnt;
  
  while (str.length > 4) {
    var flag = parseInt(str.substring(0, 4), 16);
    switch (flag) {
      case 0x0768:// Humidity
        var humidity = {};
        humidity.value =  parseFloat(((parseShort(str.substring(4, 6), 16) * 0.01 / 2) * 100).toFixed(1)); // Unit: %RH
        humidity.timestamp =  timestamp;
        humidity.context =  context;
        data.humidity = humidity;
        str = str.substring(6);
        break;
      case 0x0673:// Atmospheric pressure
        var pressure = {};
        pressure.value = parseFloat((parseShort(str.substring(4, 8), 16) * 0.1).toFixed(2)); // Unit: hPa
        pressure.timestamp =  timestamp;
        pressure.context =  context;        
        data.barometer = pressure;
        str = str.substring(8);
        break;
      case 0x0267:// Temperature
        var temperature = {};
        temperature.value = parseFloat((parseShort(str.substring(4, 8), 16) * 0.1).toFixed(2)) ; // Unit: °C
        temperature.timestamp =  timestamp;
        temperature.context =  context;   
        data.temperature = temperature;
        str = str.substring(8);
        break;
      case 0x0402:// Gas Resistance
        var gasresistance= {};
        gasresistance.value =  parseFloat((parseShort(str.substring(4, 8), 16) * 0.01).toFixed(2)) ; // Unit: KΩ
        gasresistance.timestamp =  timestamp;
        gasresistance.context =  context;           
        data.gasResistance= gasresistance;
        str = str.substring(8);
        break;
      case 0x0802:// Battery Voltage
        var voltage = {};
        voltage.value = parseFloat((parseShort(str.substring(4, 8), 16) * 0.01).toFixed(2)); // Unit: Volts
        voltage.timestamp =  timestamp;
        voltage.context =  context;           
        data.battery = voltage;
        str = str.substring(8);
        break;
      case 0x0c65:// Luminosity Sensor
        var luminosity = {};
        luminosity .value = parseFloat((parseShort(str.substring(4, 8), 16) ).toFixed(4)); // Unit: Volts
        luminosity .timestamp =  timestamp;
        luminosity .context =  context;           
        data.lux = luminosity ;
        str = str.substring(8);
        break;        
      default:
        str = str.substring(7);
        break;
    }
  }
  return data;
}