Extending Cayenne data types

Safrone · December 3, 2018, 11:54pm

Currently the Cayenne LPP supports a number of data types show in https://mydevices.com/cayenne/docs/lora/#lora-cayenne-low-power-payload-examples-downlink-message

I have a Cayenne capable device that occasionally sends its battery level using a non-standard data type as shown below:
Screenshot%20from%202018-12-03%2017-15-09

Is there an easy way to add this data type to the cayenne decoder?

If not, is there a custom javascript implementation for the cayenne decoding I could extend to fit any extra data types?

Thank you!

brocaar · December 9, 2018, 2:52pm

This is (currently) not possible. When devices are not following the defined LPP implementation (https://mydevices.com/cayenne/docs/lora/#lora-cayenne-low-power-payload), then you either have to modify the LoRa App Server source to implement this yourself, or define your own JS custom decoder to handle these cases.

Safrone · December 10, 2018, 6:10pm

That’s what I figured.

I don’t know how hard it would be to implement within the custom JS but it would be cool to basically have a try catch wrapping the Cayenne decoder so I could say, in case cayenne fails -> try the custom code.

Safrone · April 12, 2019, 7:26pm

In case anyone has the same issue, I found a JS implementation of Cayenne lpp decoding and adapted it to match the default cayenne decoder output: I didn’t write the Encode portion but I don’t know how necessary it is…

gist.github.com

https://gist.github.com/Safrone/800b44ce9632f68e7639d93ac0438076

gistfile1.txt

// Decode decodes an array of bytes into an object.
//  - fPort contains the LoRaWAN fPort number
//  - bytes is an array of payload, e.g. [225, 230, 255, 0]
// The function must return an object, e.g. {"temperature": 22.5}
function Decode(fPort, bytes) {
    /**
     * @reference https://github.com/myDevicesIoT/cayenne-docs/blob/master/docs/LORA.md
     *
     * Added types for Tektelic Sensor
     * Adapted for lora-app-server from https://gist.github.com/iPAS/e24970a91463a4a8177f9806d1ef14b8

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Safrone · April 15, 2019, 7:59pm

I ended up extending via the go code since I didn’t want to have to deal with the encoding portion via js:

I ended up having to copy a lot of code because of how go type inheritance works (or at least my limited go experience). It probably is possible to make the encode/decode code portions more object oriented so the CayennLPP is easier to extend.

hemanth_naidu · July 17, 2019, 1:28pm

Hi @Safrone. Were you able to extend datatype during encoding also?

Safrone · September 11, 2019, 6:38pm

I copied the encoding/decoding format for the cayenne payloads so both should work like the standard cayenne codec