# How to decode CBOR in a payload format Decoder?

**URL:** <https://www.thethingsnetwork.org/forum/t/how-to-decode-cbor-in-a-payload-format-decoder/36373>\
**Category:** Application Development\
**Created:** [April 21, 2020, 7:09pm UTC](https://www.thethingsnetwork.org/forum/t/how-to-decode-cbor-in-a-payload-format-decoder/36373 "2020-04-21T19:09:41Z")\
**Posts on this page:** 1\
**Showing post:** 2

<div class="post-metadata">

**Author:** ![arjanvanb](https://www.thethingsnetwork.org/forum/user_avatar/www.thethingsnetwork.org/arjanvanb/32/46626_2.png) [@arjanvanb](https://www.thethingsnetwork.org/forum/u/arjanvanb)\
**Post date:** [April 22, 2020, 8:29am UTC](https://www.thethingsnetwork.org/forum/t/how-to-decode-cbor-in-a-payload-format-decoder/36373/2 "2020-04-22T08:29:01Z")

</div>

I cannot get your example to decode in the decoder. But it’s not always going to be 48 bits, but depends on the actual value:

> [@Sending "cooked" JSON data to AllThingsTalk](https://www.thethingsnetwork.org/forum/t/sending-cooked-json-data-to-allthingstalk/31470/3):
>
> But even the binary CBOR just requires too many bytes for just a simple value. Like in this example:
> 
> > In RDK example, your temperature sensor reads 23 degrees Celsius, and you’d like to see that value in Maker. You can use [cbor.me](http://cbor.me/) to convert the payload to CBOR, e.g,
> > 
> > `{"temperature": 23}` translates to `A1 6B 74 65 6D 70 65 72 61 74 75 72 65 17`
> 
> While the plain text `{"temperature": 23}` would be 19 bytes, the above CBOR’d version is still 14 bytes for a single _integer_ value!
> 
> Even when using `{"t": 23}`, you’d still get 4 bytes for `A1 61 74 17`. A fixed position encoding, with an unrealistic temperature accuracy of 2 decimals, would allow for -327.68 thru 327.67 in just 2 bytes.
> 
> Adding a decimal in CBOR, `{"t": 23.5}` yields 6 bytes in `A1 61 74 F9 4D E0`. But other values might go crazy, like `{"t": 23.4}` yields the whopping `A1 61 74 FB 40 37 66 66 66 66 66 66`. Play around with [http://cbor.me/](http://cbor.me/) before considering using CBOR.

So, even when not using JSON, I’d fix the problem at its root cause, and try to get rid of CBOR. Unless your device sends a lot of different types of messages, it’s just too much overhead to use in LoRaWAN. And even if it does send a lot of different messages, then see, e.g., [Multiple sensors with different payload decoding TTN](https://www.thethingsnetwork.org/forum/t/multiple-sensors-with-different-payload-decoding-ttn/30351) and [How to best write an application that contains many nodes with different measure data types](https://www.thethingsnetwork.org/forum/t/how-to-best-write-an-application-that-contains-many-nodes-with-different-measure-data-types/6916).

If you really cannot get rid of it, then you’ll need to copy a CBOR helper into the payload format in TTN Console, and use that helper in the Decoder function. See [Implementations on the CBOR website](http://cbor.io/impls.html).

---

_[View the full topic](https://www.thethingsnetwork.org/forum/t/how-to-decode-cbor-in-a-payload-format-decoder/36373)._