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Bytes  | 0   | 1 .. len-3      | len-2 . len-1  | len   |
       +-----+-----------------+----------------+-------+
Field  | len | Modbus response | start register | count |

Reference Decoder

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This is a decoder written in JavaScript that can be used to parse the device's LoRaWAN messages. It can be used as is

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in The Things Network.

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Code Block
function readVersion(bytes) { if (bytes.length<3) { return null; } return "v" + bytes[0]

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218function readVersion(bytes) {
    if (bytes.length<3) {
        return null;
    }
    return "v" + bytes[0]

+ "." + bytes[1] + "." + bytes[2];

function int40


 
function int40_BE(bytes, idx)

{
bytes =

 {
    bytes = bytes.slice(idx || 0);

return bytes


    return bytes[0] << 32 |

bytes


        bytes[1] << 24 | bytes[2] << 16 | bytes[3] << 8 | bytes[4] << 0;

function int16


 
function int16_BE(bytes, idx)

{
bytes =

 {
    bytes = bytes.slice(idx || 0);

return bytes


    return bytes[0] << 8 | bytes[1] << 0;

function uint16


 
function uint16_BE(bytes, idx)

{
bytes =

 {
    bytes = bytes.slice(idx || 0);

return bytes


    return bytes[0] << 8 | bytes[1] << 0;

function port1


 
function port1(bytes)

{
return {

 {
    return {
        "port":1,


        "version":readVersion(bytes),


        "flags":bytes[3],


        "temp": int16_BE(bytes, 4) / 10,


        "vBat": int16_BE(bytes, 6) / 1000,


        "timestamp": int40_BE(bytes, 8),


        "operationMode": bytes[13],


        "noData": !!(bytes[3] & 0x01)

};

function port2


 
function port2(bytes)

{
var regs =

 {
    var regs = [];

if


    if (bytes.length > 5) {


        // loop through data

packs
var b =

 packs
        var b = bytes.slice(5);

while


        while (b.length>=4)

{
var r = {

 {
            var r = {
                "device":b[0],


                "register":int16_BE(b, 1),


                "count":b[3] & 0x3f,


                "error":!!(b[3]>>7),


                "data":null

};

var dataLen =


            var dataLen = r["count"]*2;

if


            if (b.length >= dataLen+4) {

r


                r["data"] = b.slice(4, 4 + dataLen);

regs


            regs.push(r);

b =


            b = b.slice(4+dataLen);

return {


    return {
        "port":2,


        "timestamp": int40_BE(bytes, 0),


        "registers": regs

};

function modbusErrorString


 
function modbusErrorString(code) {


    // Modbus exception codes

//

see https

 see https://en.wikipedia.org/wiki/Modbus#Exception_responses

switch


    switch (code)

{
        case 1:
            return "Illegal Function";
        case 2:
            return "Illegal Data Address";
        case 3:
            return "Illegal Data Value";
        case 4:
            return "Slave Device Failure";
        case 5:
            return "Acknowledge";
        case 6:
            return "Slave Device Busy";
        case 7:
            return "Negative Acknowledge";
        case 8:
            return "Memory Parity Error";
        case 10:
            return "Gateway Path Unavailable";
        case 11:
            return "Gateway Target Device Failed to Respond";
        default:
            return "Unknown error code";
    }
}

function parseModbusPayloadRegisters(payload) {
    if (payload.length < 1) {
        return null;
    }
    var byteCnt = payload[0];
    if (payload.length !== byteCnt + 1) {
        return null;
    }
    var vals = [];
    for (var i=0; i<byteCnt; i+=2) {
        vals

 {
        case 1:
            return "Illegal Function";
        case 2:
            return "Illegal Data Address";
        case 3:
            return "Illegal Data Value";
        case 4:
            return "Slave Device Failure";
        case 5:
            return "Acknowledge";
        case 6:
            return "Slave Device Busy";
        case 7:
            return "Negative Acknowledge";
        case 8:
            return "Memory Parity Error";
        case 10:
            return "Gateway Path Unavailable";
        case 11:
            return "Gateway Target Device Failed to Respond";
        default:
            return "Unknown error code";
    }
}
 
function parseModbusPayloadRegisters(payload) {
    if (payload.length < 1) {
        return null;
    }
    var byteCnt = payload[0];
    if (payload.length !== byteCnt + 1) {
        return null;
    }
    var vals = [];
    for (var i=0; i<byteCnt; i+=2) {
        vals.push([+payload[i+1], +payload[i+2]])

return vals;

}
function parseModbusResponse


    return vals;
 
}
function parseModbusResponse(raw)

{
var resp =

 {
    var resp = {};

if


    if (raw.length >= 6)

{
var fun =

 {
        var fun = raw[1] & 0xf;

var error =


        var error = !!(raw[1] & 0x80);

var rawResp =


        var rawResp = raw.slice(0, raw.length - 3);

resp


        resp["slave"] = raw[0];

resp


        resp["function"] = fun;

resp


        resp["error"] = error;

resp


        resp["start"] = uint16_BE(raw, raw.length - 3);

resp


        resp["cnt"] = raw[raw.length - 1];

resp


        resp["raw"] = rawResp;

if


        if (error) {

resp


            resp["errorCode"] = raw[2];

resp


            resp["errorText"] = modbusErrorString(raw[2]);

else {
resp

 else {
            resp["values"] = parseModbusPayloadRegisters(rawResp.slice(2))


            // TODO: coils

return resp;
}

function FullResponses


    return resp;
}
 
function FullResponses(bytes, port)

{
var timestamp =

 {
    var timestamp = int40_BE(bytes);

    var pos = 5;
    var resps = [];
    while (pos <


    var pos = 5;
    var resps = [];
    while (pos < bytes.length)

{
var respLen =

 {
        var respLen = bytes[pos++];

if


        if (bytes.length >= pos + respLen)

{
var rawResponse =

 {
            var rawResponse = bytes.slice(pos, pos + respLen);

resps


            resps.push(parseModbusResponse(rawResponse));

pos


            pos += respLen;

else {
            break;
        }
    }
    return {

 else {
            break;
        }
    }
    return {
        "port": port,


        "timestamp" : timestamp,


        "responses": resps

};

function bin2String


 
function bin2String(array)

{
var result

 {
    var result = "";

for (var i =


    for (var i = 0; i < array.length; i++)

{
result

 {
        result += String.fromCharCode(array[i]);

return result;
}

function ConfigResponse


    return result;
}
 
function ConfigResponse(data)

{
var t =

 {
    var t = bin2String(data);

return {


    return {
        "response" : t,


        "error" : (t.length === 0) || (t[0] === '!')

/**


 * TTN decoder function.

*/

function Decoder


function Decoder(bytes, port)

{
switch

 {
    switch (port)

{
case 1:

 {
        case 1:
            // Status message:

return port1


            return port1(bytes);

case 2:


        case 2:
            // not legacy format:

return port2


            return port2(bytes);

case 3:
case 4:


        case 3:
        case 4:
            // v1.0.0 format, full modbus responses:

return FullResponses


            return FullResponses(bytes, port);

case 5:


        case 5:
            // continuation of previous response:

return


            return {};

case 6:


        case 6:
            // dense format with prefixed timestamp:

return


            return {};

case 7:


        case 7:
            // dense format without timestamp:

return


            return {};

case 128:
return ConfigResponse


        case 128:
            return ConfigResponse(bytes);

return


    return {"error":"invalid port", "port":port};

/**


 * LoRaServer decoder function.

*/

function Decode


function Decode(fPort, bytes) {


    // wrap TTN Decoder:

return Decoder


    return Decoder(bytes, fPort);

}
function Parse


}
function Parse(input)

{
var data =

 {
    var data = bytes(atob(input.data));

var port =


    var port = input.fPort;

var fcnt =


    var fcnt = input.fCnt;

var vals


    var vals =  Decoder(data, port);

vals


    vals["port"] = port;

vals


    vals["data"] = data;

vals


    vals["fnct"] = fcnt;

var lastFcnt =


    var lastFcnt = Device.getProperty("lastFcnt");

vals


    vals["reset"] = fcnt <= lastFcnt;

Device


    Device.setProperty("lastFcnt", fcnt);

return vals;


    return vals;
}

Compact Payload Format (Port 20, (21-59) PlFmt=4&5)

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Versions Compared

Old Version 48

New Version 49

Key

Reference Decoder

Compact Payload Format (Port 20, (21-59) PlFmt=4&5)