Where to configure the formatter to upload data to Thingspeak

TTN Network and Services The Things Stack v3
1

Hi There!
Im setting up my new device (Elsys CO2 thru Dragino LPS8 gw)
My end goal is to get this information on ThingSpeak
I already created a webhook->Thingspeak, and provided the channel ID and Write API KEY
Only thing Im missing (I believe) is creating the payload formatter
I see two possible places for this to be and Im unsire which one should have it:

  1. Applications->App1->Payload Formatters->Uplink->Custom Javascript formatter
  2. Applications->App1->End Devices->Dev1->Payload Formatters

My idea is to assign a var to each field Im reading from the Elsys CO2 monitor, and “return” each of these as a variable to the ThingSpeak fields.

Which place to chose? Or am I misunderstanding the whole thing…?

Thanks!

2

Also, I wanted to add another question. All samples of formatters I can find for ThingSpeak are in the format of

function Decoder(b, port) {
var var1 = b[0];
var var2 = b[1];

return {
field1: var1,
field2: var2,

}
}

BUT in both places I find formatters in TTN the function starts with
function decodeUplink(input) {…

Why? Are we talking about the same?

Thanks!

3

This is the application formatter and will be used for any device that does not have it’s own PF.

This would be a PF for the Dev1 device only - no other devices would access it

That is EXACTLY what a payload formatter is for.

That is the v2 format of The Things Stack - it does work but isn’t optimal.

You may benefit from reading the documentation on payload formatters - both in the device & the reference section.

And maybe look on the Elsys site for a PF? And ask Thingspeak about their out of date documentation?

4

Ok, understood.
So this is what I did.
I firstly selected the “Use Device repository formatters”. This looks like a sample decoder script for the specific device Im using, but not specifically aimed at ThingSpeak
From this file I took the initial variables and all the functions to assemble multibyte data, and then put this specific section at the end

function decodeUplink(input) {

return {
    
	field1:TYPE_CO2,
	field2:TYPE_TEMP,
	field3:TYPE_RH,
	field4:TYPE_LIGHT,
	field5:TYPE_MOTION,
}

}

Anyway I can’t check the forwarding yet as my device is not operational yet but I will be able the test it shortly

Thanks!

5

Ok I realized that my formatter wouldnt work, I wasn’t understanding what every line would do.
Now it looks like this:

function decodeUplink(input) {
  var data = {}
  var b = input.bytes;
  var temp=(b[0] << 8) | b[1];
  var hum=b[2];
  var luz=(((b[6] << 8) | b[7]) <<8 )|b[8];
  var mov=b[9];
  var co2=(b[10] << 8) | b[11];
  
  
  data.field1 = co2;
  data.field2 = temp;
  data.field3 = hum;
  data.field4 = luz;
  data.field5 = mov;
  
  return {
    data: data
  };
}

When my device is ready I will keep you posted

6

Along your journey, please be aware that we can only mark homework that is properly formatted - </> is not your friend, it is your gateway to making friends.

7

Edited, sorry