# Set Hex Value in a Change Node
**URL:** https://discourse.nodered.org/t/set-hex-value-in-a-change-node/15917
**Category:** General
**Created:** [25 September 2019 22:00 UTC](https://discourse.nodered.org/t/set-hex-value-in-a-change-node/15917 "2019-09-25T22:00:01Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@dudleyjosh](https://discourse.nodered.org/u/dudleyjosh)
#### Post date: [25 September 2019 22:00 UTC](https://discourse.nodered.org/t/set-hex-value-in-a-change-node/15917/1 "2019-09-25T22:00:02Z")
If need to send the hex value of 0x18 to a serial port node, what is the proper way to do it using a Change node? I've found that is can be done using the following string "\u0018" within a JSONata expression field (I don't exactly understand why) but I am wondering if I am missing something simple and if there is a better way?
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### Author:  [@shrickus](https://discourse.nodered.org/u/shrickus)
#### Post date: [26 September 2019 02:00 UTC](https://discourse.nodered.org/t/set-hex-value-in-a-change-node/15917/2 "2019-09-26T02:00:29Z")
There are several places where you can enter data as a byte array, e.g. `inject` and `change` nodes. However, the implementation of the input editor is a bit... obscure:
If you read the Info panel closely, you _may_ discover that you can enter an array of "character codes", which will be stored as their byte equivalents -- but I doubt it. I had to be shown this by Dave himself...
In JSON syntax, `["0x18"]` represents an array of 1 byte, with hex value `18` -- where as if that character is entered as `["18"]`, it's interpretted as 1 char of **decimal** value 18 and stored as the hex byte `12`
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### Author:  [@dudleyjosh](https://discourse.nodered.org/u/dudleyjosh)
#### Post date: [26 September 2019 02:39 UTC](https://discourse.nodered.org/t/set-hex-value-in-a-change-node/15917/3 "2019-09-26T02:39:50Z")
Thanks @shrickus, I'll give it a try tomorrow.
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### Author:  [@dudleyjosh](https://discourse.nodered.org/u/dudleyjosh)
#### Post date: [26 September 2019 20:47 UTC](https://discourse.nodered.org/t/set-hex-value-in-a-change-node/15917/4 "2019-09-26T20:47:18Z")
@shrickus I had a chance to mess with that today and this is what I found...
If I send the buffer value ["0x18"] directly to the serialport it does not work the same as if I send it the JSONata string value of "\u0018". However, if I perform a toString() operation on the buffer value, then send it to the serialport, it works as expected/needed?
I wish I understood why?
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### Author:  [@shrickus](https://discourse.nodered.org/u/shrickus)
#### Post date: [27 September 2019 01:08 UTC](https://discourse.nodered.org/t/set-hex-value-in-a-change-node/15917/5 "2019-09-27T01:08:03Z")
Ah, me too -- only thing I can think of is that the buffer is only 1 byte long, where the character string (of 1 char) is actually 2 bytes?
If the protocol expects 2 bytes, you _might_ want to try left padding with 0, so `["0x00", "0x18"]`?