Greetings,
I, as most people, am working to create an RTU that utilizes the MQTT communications protocol. Right now I am testing with a local broker and have data reliably getting to VTScada.
However, I need the ability to write data back to a certain topic with a certain metric. The ability seems to exist, yet I have not had any luck with VTScada publishing the message correctly yet.

Using JSON formatting lets say I wanted the data to write like this
{"LSP":XX.XX}

Where...
Topic: DD/Write
Metric: LSP

and XX.XX is the value input to my analog widget.

Right now when I try to get my data to publish as such, I get the topic == DD/Write, but the metric is no where to be found in the message. The only data in the message is the integer entered.

See the attached image for how I have my write address set up.

The MQTT Publisher is built to only publish the value to the topic and ignores the metric. There are specific reasons for this but I am not aware of the details as to why this behaviour was chosen.

If you want, you can create a custom decoder for the MQTT driver which will work for you. An example snippet of code which should be able to get you started is shown below:

Help on writing a custom MQTT Decoder: https://www.vtscada.com/help/Content/Scripting/Tasks/pro_MQTTParser.htm

{=========================== JSONEncoder ===================================}
{ Computes a Payload in a JSON format to Publish via MQTT }
{===========================================================================}
(
Data { A value to be written out. };
MemAddr { "Indexing trail" from the Write address of the IO };

)
[
X;
JsonDict;
]

Only [
If Watch(1);
[
JsonDict = Dictionary();
JsonDict[MemAddr] = Data;
JsonDict["Timestamp"] = CurrentTime(1); { Now }

X = JSonEncode(JsonDict);

Return(X);
]
]

Note, implementing this requires a more advanced knowledge of VTScada. If you have SupportPlus, I'd encourage you to reach out to our support team for assistance here.

Dave, you are the man! This works like a charm!

Thanks for following up. I'm glad that this worked well for you and that you were able to get it implemented. The code came from our dev team so I can't take credit for it; I'm just the messenger