No multiple topics

General
1

Hi.
I´m pretty new in Node-Red, but I´m trying to understand it better every day.
Actually I want to transfer MQTT of my heat pump to my PLC with ADS.
But I don´t want to use 100´s of MQTT nodes, just only one with /# and then use only the ones I need.
But how can I do that, to filter for subtopics ?
Thanks.

Regards, Thorsten

2

That would depend on your topic structure, any answer would be a guess as you do not provide examples of your topics.

you could use a look up object and see if your incoming topic is in the look up object.
Or
you could split your topic on "/" and only pass if a certain array value is something you want to pass.

3

Hi.
The structure is for example "panasonic_heat_pump/main/Heatpump_Status" or "panasonic_heat_pump/main/Main_Inlet_Temp".
Behind main/ is one of my suptopics and every subtopic has a value.
So I´m using "panasonic_heat_pump/main/# for calling every subtopic.

4

You can use a Switch node to send the message down the different routes by testing msg.topic in the Switch rules.

5

so spliting your topic on "/" and selecting an array index would produce a string
msg.topic = msg.topic.split("/")[2];
outputs
"Heatpump_Status"
you could then compare in function or switch node for that value.

6

Isn't it easier just to test the topic directly in the Switch node?

7

That depends on how long your topic is, I just prefer not having to type long strings, It's just a personnel choice.

Also it allows for different topics starts with same final section

e.g.
one/two/status
four/five/status

both would be passed

8

All subtopics just have numbers as a value, no strings.
example

MQTT directly to ADS, no visu with Node-Red

9

I am not talking about values, I am showing an example of directing message via msg.topic, which holds the mqtt topic.

10

Switch is working fine for me:
result

11

You can use one Switch node with multiple rules, sending each topic to its own output.

12

Yes, I´ve seen it.
For heatpump states I´m having 9 rules and changing numbers to strings. It´s working fine.

13

How can I do this in the other way ?
Signals are coming from PLC, for example "1", and must be sent to panasonic_heat_pump/main/SetOperationMode.
But I´m also using /# for the MQTT-Out.
With the change node it´s not working.

14

As described in the help text for the node, leave the topic blank in the Out node and put the topic in msg.topic. In fact I believe that is the original reason that msg.topic is called msg.topic.

1 Like
15

against missunderstanding:
"ADS Notification" -> "CHANGE" with 2 rules: bolean to number & msg.topic with the full path -> "MQTT-Out" with blank topic ?

16

Sorry, that conveys nothing to me.

17

sorry, but I´m having the solution.
Using change node with setting msg.topic to the path and leaving the OUT blank. Thanks.

18

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