Agoraopinion Feedback Button Payload decoder

hi all, i have some problems in getting a payload decoder in js for "agoraopinion feedback buttons"working proper. This device has 3 action keys(red,yellow,green). i took an already existing script and modify it. my solution shows only 2 of the 3 buttons that got triggered. i am totaly new to js. would be fine if you could help me. thanks

Here my solution:

var TYPE_PTYPE		= bytes[-2]; //Payload type
var TYPE_YELLOW		= bytes[2]; //Leftbutton
var TYPE_GREEN		= bytes[4]; //middle button
var TYPE_RED        = bytes[0]; //right button 
var TYPE_BL			= bytes[6]; //Battery Level
var TYPE_DI			= bytes[8]; //Device ID
function bin16dec(bin) {
    var num=bin&0xFFFF;
    if (0x8000 & num)
        num = - (0x010000 - num);
    return num;
function bin8dec(bin) {
    var num=bin&0xFF;
    if (0x80 & num) 
        num = - (0x0100 - num);
    return num;

function hexToBytes(hex) {
    for (var bytes = [], c = 0; c < hex.length; c += 3)
		bytes.push(parseInt(hex.substr(c, 2), 16));      
    return bytes;
function DecodeSmileybox(bytes){
    var obj = new Object();
            case TYPE_PTYPE: //Payloadtype
            case TYPE_YELLOW: //left button
            case TYPE_GREEN: //middle button
      [i+1]>>4); //[i+1]);
            case TYPE_RED: //right button
            case TYPE_BL: //Battery Level
            case TYPE_DI: //Device ID
            default: //somthing is wrong with data
    return obj;
function Decode(fPort, bytes) {
  return DecodeSmileybox(bytes);

here its documentation: [EN] Payload information V5.pdf (1014.7 KB)

i really don’t know how to solve it.
fine if you could help me thanks


Okay, this is indeed a literal repost of your Slack post :slight_smile:

Let me repeat my remarks/questions too then:

The PDF document shows a text-based message, assuming you indeed get 16 bytes (or 14), not 8 (or 6), for the first message type that’s described in the PDF. That is not only quite bad for LoRaWAN (a big waste of airtime), but also complicates things a lot. Also, it does not at all match the script you’ve got so far: the script seems to expect a specific message whenever a button is pressed, rather than some totals as per the PDF.

So: it would help to see actual payloads as received in your application (TTN Console) along with the values that you think this should decode into.

mqtt shows me this here:
“adr” : true,
“fCnt” : 9,
“fPort” : 5,
“data” : “AgDADQDF”

the decoded data in hex will be look like this:

02 - is the payload type (here voting)
00c - red button
00d - yellow button
00c - green button
5 - should be the batterylevel

hope this is helpful. thanks

Good, it’s not text! Even more, it only uses 1.5 bytes for a single count, not wasting anything at all. Many would simply have used 2 bytes per counter. :slight_smile:

Then the following might work? Note that it uses a fixed-format decoder; not some loop that iterates over the payload and tries to determine how to interpret the next part by comparing to some known values, like in your attempt:

 * Decoder for Agora Opinion feedback button.
function Decoder(bytes, port) {
  var result = {};
  result.payloadType = bytes[0];

  // 1.5 bytes (3 nibbles) per count, plus 0.5 byte for battery,
  // encoded in 5 bytes; rr ry yy gg gb
  result.redCount = bytes[1]<<4 | bytes[2]>>4;
  result.yellowCount = (bytes[2] & 0x0F)<<8 | bytes[3];
  result.greenCount = bytes[4]<<4 | bytes[5]>>4;

  // Unary-plus operator to cast string result of toFixed to number
  result.batteryVoltage = 
      +((3 * 1.224) / (((bytes[5] & 0x0F) + 20) / 21)).toFixed(1);

  return result;

To explain the bitwise operators, for the 5 bytes rr ry yy gg gb, all in hexadecimal notation using two 4-bits nibbles for each 8-bits byte:

  • rr << 4 appends a nibble to the right, so yields rr0 (left shift of 4 bits; actually the result is 32 bits, so 00000rr0)
  • ry >> 4 shifts the rightmost nibble out of memory, so discards y and yields r (right shift; actually 0000000r)
  • rr0 | r yields rrr (bitwise OR)
  • ry & 0x0F yields y (bitwise AND)
  • y << 8 yields y00
  • y00 | yy yields yyy

Easy! :nerd_face:

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Thanks for your quick help. i will test it, when i will be back in office and come back to you with the result.

So, where’s the result…? :frowning:

Sorry for my delayed answer to this topic, the result for this issue looks really fine now.

"txInfo" : { "frequency" : 868300000, "dr" : 0 }, "adr" : true, "fCnt" : 51, "fPort" : 5, "data" : "BAEACwIl", "object" : { "battery" : 3.1, "greenCount" : 34, "orangeCount" : 11, "payloadType" : 4, "redCount" : 16 }"

Thank you again for you help :slight_smile:

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