Data TTN to Thingspeak problem with Payload Decoder from Array

Hello,

I have a question regarding decoding in TTN specifically for Thingspeak.

The code in Arduino IDE for a MKR1310 is the following:

String sensorString = String(airTemperatureReading);// + "-" + String(altitudeReading)+ "-" + String(pressureReading)+ "-" + String(sensorValueRain);
  char payload[sensorString.length()+1];
  sensorString.toCharArray(payload, sensorString.length() +1);
  Serial.print(payload);
  .
  .
  .
  modem.beginPacket();
     
    modem.write(payload, sizeof(payload));

Here I tested just one sensor data, to make it easier to understand whats going on with the payload function in general. But I didn´t really manage with that. In TTN the decoding is ok, so I get with the decoder -just for TTN usage- 24 from Hex 323400. However, now I have to switch the decoder to Thingspeak readable data but with the following Decoder I just get 50 in field1, but 24°C is the right temperature.

Decoder TTN:

    function Decoder(bytes, port)
 {
   var tem = (bytes[0]<<0) | bytes[0];

     return {
        field1: tem
     }
  }

Test Byte Payload -> Complete uplink data

    
    {
  "f_port": 3,
  "frm_payload": "MjQA",
  "decoded_payload": {
    "field1": 50
    .
    .
    .

The complete Arduino Sketch is from here:

https://github.com/InfluxCommunity/plant_buddy/blob/master/microcontroller/thing_network/plant_buddy_arduino_MKR_1310.ino

Thank you very much

[Christopher Stapels]

Can you clarify what the question you ar asking is?

[Karsten Fenske]

The question is, how to decode the payload - > an array of strings (sensor data for example temperature) sent to TTN, into readable format for Thingspeak?

Answer 1

[Christopher Stapels]

Around 4:01 in this video, I'm explaining my payload formatter. Or you can see the instructions in this example in the doc. The doc is a bit outdated for TTN, (version 2 instead of 3) but the payload formatting is still true. The video is up to date for version 3.

[Jörn]

Broken link

[Christopher Stapels]

Do you mean this video link in the post above? I just tried it and it worked for me at https://www.youtube.com/watch?v=b9Ga4nwnsTM

[Seamus]

Hi,

I am also looking for a TTN Thingspeak payload formatter template. The link to the example document above is broken. Could you post the code here please? Any help much appreciated. Linking a DL-CTD10 - Pressure / Liquid Level, Temperature and Electrical Conductivity Sensor to thingspeak but having difficulty in getting correct format.

[Christopher Stapels]

Thanks for pointing out the broken link. Apparently I truncated the 'l' at the end of 'html'. Its fixed now, but I have to warn you, TTN changes things pretty fast as far as I can tell, and I havent kept up on their formatting too much. If you get it working, please let us know.