downlink-decoder.js

/*
Decoding downlink messages received by https://dev.disk91.com/fieldtester/ttn/v3 webhook
See https://github.com/disk91/WioLoRaWANFieldTester/blob/master/doc/DEVELOPMENT.md
*/
function encodeDownlink(input) {
  return {
    bytes: [],
    fPort: 1,
    warnings: [],
    errors: []
  };
}

/*
Byte 	Usage
0 	Sequence ID % 255
1 	Min Rssi + 200 (160 = -40dBm)
2 	Max Rssi + 200 (160 = -40dBm)
3 	Min Distance step 250m
4 	Max Distance step 250m
5 	Seen hotspot
*/
function decodeDownlink(input) {
  errors = [];
  if(input.fPort == 2){
    data = {};
    data.sequece = input.bytes[0];
    data.min_rssi = input.bytes[1]-200;
    data.max_rssi = input.bytes[2]-200;
    data.min_distance = (input.bytes[3] * 250) + "m";
    data.max_distance = (input.bytes[4] * 250) + "m";
    data.hotspots = input.bytes[5];
  }else{
    data = input.bytes;
    errors = "Can only decode fPort 2 messages"
  }

  return {
    data: data,
    warnings: [],
    errors: errors
    }
}

uplink-decoder.js

// For details see https://github.com/disk91/WioLoRaWANFieldTester/blob/master/doc/DEVELOPMENT.md

function Decoder(bytes, port) {
	var decoded = {};
	// avoid sending Downlink ACK to integration (Cargo)
	var lonSign;
	var latSign;
	var encLat;
	var encLon;
 
	if (port === 1) { 
    // Decode normal messages
		lonSign = (bytes[0] >> 7) & 0x01 ? -1 : 1;
		latSign = (bytes[0] >> 6) & 0x01 ? -1 : 1;

		encLat = ((bytes[0] & 0x3f) << 17) +
			(bytes[1] << 9) +
			(bytes[2] << 1) +
			(bytes[3] >> 7);

		encLon = ((bytes[3] & 0x7f) << 16) +
			(bytes[4] << 8) +
			bytes[5];

		var hdop = bytes[8] / 10;
		var sats = bytes[9];

		const maxHdop = 2;
		const minSats = 5;

		if ((hdop < maxHdop) && (sats >= minSats)) {
			// Send only acceptable quality of position to mappers
			decoded.latitude = latSign * (encLat * 108 + 53) / 10000000;
			decoded.longitude = lonSign * (encLon * 215 + 107) / 10000000;
			decoded.altitude = ((bytes[6] << 8) + bytes[7]) - 1000;
			decoded.accuracy = (hdop * 5 + 5) / 10
			decoded.hdop = hdop;
			decoded.sats = sats;
		} else {
			decoded.error = "Need more GPS precision (hdop must be <" + maxHdop +
				" & sats must be >= " + minSats + ") current hdop: " + hdop + " & sats:" + sats;
		}
		return decoded;
	} else 	if (port === 3) {
    // Decode discovery messages
		lonSign = (bytes[0] >> 7) & 0x01 ? -1 : 1;
		latSign = (bytes[0] >> 6) & 0x01 ? -1 : 1;

		encLat = ((bytes[0] & 0x3f) << 17) +
			(bytes[1] << 9) +
			(bytes[2] << 1) +
			(bytes[3] >> 7);

		encLon = ((bytes[3] & 0x7f) << 16) +
			(bytes[4] << 8) +
			bytes[5];
		
		decoded.latitude = latSign * (encLat * 108 + 53) / 10000000;
		decoded.longitude = lonSign * (encLon * 215 + 107) / 10000000;
		return decoded;
  }
	return null;
}

// TTN v3 workaround from  https://gist.github.com/tiefpunkt/9407f4049365c065fdd6905adf949993
function decodeUplink(input) {
  var data = input.bytes;
  var valid = true;

  if (typeof Decoder === "function") {
    data = Decoder(data, input.fPort);
  }

  if (typeof Converter === "function") {
    data = Converter(data, input.fPort);
  }

  if (typeof Validator === "function") {
    valid = Validator(data, input.fPort);
  }

  if (valid) {
    return {
      data: data
    };
  } else {
    return {
      data: {},
      errors: ["Invalid data received"]
    };
  }
}