# Use external value for BACnet write node?
**URL:** https://discourse.nodered.org/t/use-external-value-for-bacnet-write-node/42469
**Category:** General
**Created:** [11 March 2021 10:24 UTC](https://discourse.nodered.org/t/use-external-value-for-bacnet-write-node/42469 "2021-03-11T10:24:33Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@Graves](https://discourse.nodered.org/u/Graves)
#### Post date: [11 March 2021 10:24 UTC](https://discourse.nodered.org/t/use-external-value-for-bacnet-write-node/42469/1 "2021-03-11T10:24:34Z")
I have been using the `node-red-contrib-bacnet` library and everything is working perfectly, I can read and write values to my BACnet controller without an issue. I do have one problem though, I cant figure out how to use the value from another node like a timestamp as the value that is sent by the BACnet write node.
When I do it like this it writes the value perfectly:
But it does not work at all when I try to use the `msg.payload` from another node:
I have tested the `msg.payload` itself and it shows up fine in debug.
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### Author:  [@Steve-Mcl](https://discourse.nodered.org/u/Steve-Mcl)
#### Post date: [13 March 2021 09:30 UTC](https://discourse.nodered.org/t/use-external-value-for-bacnet-write-node/42469/2 "2021-03-13T09:30:23Z")
Did you read the built in help?
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### Author:  [@iiLaw](https://discourse.nodered.org/u/iiLaw)
#### Post date: [14 March 2021 22:00 UTC](https://discourse.nodered.org/t/use-external-value-for-bacnet-write-node/42469/3 "2021-03-14T22:00:23Z")
Here is an example of my function node writing a Temperature value to the Present Value of an Analogue Value object
```auto
var temp = parseFloat(msg.payload[Object.keys(msg.payload)[0]].toFixed(1));
msg.payload = {
objectId: {type: 2, instance: 201},
propertyid: 85,
values: [{type: 4, value: temp}],
priority: 8
}
return msg;
// type: 2 = Analog_Value
// Instance: 201
// propertyid: 85 = Present value
// values: [{type: 4, value: temp}] -- type 4 = Real
// wired to BACnet write node
```
---
### Author:  [@system](https://discourse.nodered.org/u/system)
#### Post date: [13 May 2021 22:01 UTC](https://discourse.nodered.org/t/use-external-value-for-bacnet-write-node/42469/4 "2021-05-13T22:01:19Z")
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