Make a TTN v2 payload decoder work with TTI/N v3

decoder.js

function Decoder(bytes, port) {
  // Your "old" TTN v2 decoder function
}

// add other functions (Converter, Validator) here if you used them. If you didn't you can just skip them.

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"]
    };
  }
}

Hi Severin,

Thank you for the fast reply. See below for example.
Using below V2 decoder and your V3 converter, the variable names "b" and "at" are not in the decoder output.
When testing with byte 0 and 1, value HEX 64, both outputs for B and at are "100"

function Decoder(bytes, port) {
// Decode an uplink message from a buffer
// (array) of bytes to an object of fields.
var decoded = {};

if (port === 2) decoded.b = bytes[0]/50;
if (port === 2) decoded.at = bytes[1]-100;

You need to return the decoded object, and then they will be. I see where you might be coming from. If you use the following Decoder function you should get what you're aiming for:

function Decoder(bytes, port) {
  // Decode an uplink message from a buffer
  // (array) of bytes to an object of fields.
  var decoded = {};
  
  if (port === 2) decoded.b = bytes[0]/50;
  if (port === 2) decoded.at = bytes[1]-100;

  return decoded;
}