MQTT value (payload) as a variable in the Windigipet 2025

[Rupert van Swol]

Hello Forum

I've started using MQTT with the WDP2025C again, and am successfully receiving data from an RFID reader on the topic:

* MPC/vPort/11 → for example, "0020" (see image.


I can also manually display text in WDP via MQTT:

* Memo: WDP/Evt/Memo/0/State
* Track diagram text: WDP/Evt/Text/18_26/State

This works well when I manually publish via the broker output 

My question is:
Is it possible within WDP2025C to use the received MQTT payload (e.g. from MPC/vPort/11) directly as a message for another MQTT action (e.g. forwarding to WDP/Evt/Text/18_26/State)?

In other words:
Can WDP dynamically pass the payload of an MQTT trigger to an MQTT output, without external tools such as Node-RED?

If so:

* How can I use the received MQTT value (payload) as a variable in the Windigipet 2025 'Track diagram text: WDP/Evt/Text/18_26/State
' field?

If not:

* Is there another recommended method within WDP to achieve this connection?

Thank you in advance for your help,
Kind regards,
Rupert van Swol

[Markus Herzog]

Hi Rupert,

there are several possibilities. Due to time issue a document with a little bit of text (without large prosa and maybe with spelling errors) as attachment.
You will see that there are several ways. Each might have its favor. Of course for really fancy message processing using NodeRed etc. as external helper is also a good idea

Regards
Markus

[Rupert van Swol]

Hello Markus, thank you for this contribution.
Once I've got it working, I'll get back to you with a description of how I achieved it.
That way, other WDP users can benefit from it too.

Kind regards,
Rupert van Swol
 

[Rupert van Swol]

Dear forum members,

I've recently testing a MegaPoints RFID reader, MQTT Explorer and Windigipet 2025c , and would like to share my findings — this might save others a lot of time searching.

Situation

RFID reader connected via MQTT
Data arrives on topics such as:MPC/vPort/10MPC/vPort/11
Windigipet does not listen to these topics.


What works
Manual publishing in MQTT Explorer (e.g. value 1602) → arrives correctly in Windigipet
RFID reader reads tags correctly → visible in MQTT Explorer
Topics and payload are correct

What doesn't work
Automatic messages from the RFID reader do not arrive reliably in Windigipet

Investigation / tests

JSON path tested → not necessary (payload is simply 1602)
Tried different topics → no difference
Changed protocol (Native ↔ JMRI) → no solution
Checked payload → correct and clean (no extra characters)

Cause
The RFID reader (MegaPoints) publishes MQTT messages with:
QoS = 0
retain = false
This means:
Message is sent once ("fire & forget")
If the receiver (Windigipet) is not listening at that moment → message is missed
No last value is stored (no retain)
MQTT Explorer does see it, because it is continuously connected.

Solution
Use an intermediary layer (e.g. Node-RED) to republish the messages with:
QoS = 1
retain = true

Example:
IN:  MPC/vPort/11
OUT: MPC/vPort/11_fixed
Set Windigipet to listen to:
MPC/vPort/11_fixed

Conclusion
The MPC hardware is working correctly
MQTT setup is correct
The limitation lies in the MQTT implementation of the reader (QoS 0, no retain)
An intermediate layer makes the system reliable

Tip
Node-RED is a simple and effective solution for this (drag-and-drop blocks, no programming knowledge required).
Hopefully this helps others who encounter the same problem

kind regards
Rupert