How can I subscribe to topics using Sparkplug B MQTT?


How can I subscribe to topics using Sparkplug B MQTT?

I understand you’re trying to enable bidirectional communication from the Ignition Gateway to your HMI (similar to a “subscribe” function). As you may have seen, Subscribe doesn’t work the same way here with Sparkplug.

I’ve attached our Guide regarding the setup for Ignition. Please see page 20 regarding enabling writes from the Ignition Gateway to your Edge Nodes (i.e. your HMI):

You will need to uncheck these two default options:

  • Uncheck ‘Block outbound edge node tag writes’
  • Uncheck ‘Block outbound device tag writes’

This allows you to write data directly to HMI tags from the Ignition Gateway itself, either through the tag browser, or by means of an Ignition Designer project that you create.

Just be aware that if your existing HMI Sparkplug Tags are set up to read in data from a PLC, if you go to write to that Tag from Ignition the value will likely be quickly overwritten again by the HMI.

Instead, if you wish to simply “receive” information from an Ignition client/gateway/designer, you may wish to create new tags on the HMI in local registers that aren’t otherwise being used. (This way they won’t be overwritten by any other device or function in the EBPro project.)

Then if you need to use the data written to these local tags elsewhere, you can set up data transfers, alarms, or use them in a macro, for example.

Content Created by Jeff Robertson
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