Using MQTT Transmissions 'Refresh' Mechanism

Prerequisites:

• Knowledge of Ignition and Module installation process: Cirrus Link Module Installation
• Install the following MQTT Modules
  
  • MQTT Distributor
    • v4.0.X if using Ignition 8.0.x
  • MQTT Engine
    
    • v4.0.X if using Ignition 8.0.x
  • MQTT Transmission
    
    • v4.0.X if using Ignition 8.0.x
• Ensure you are familiar with Transmitter configurations: MQTT Transmission Transmitters and Tag Trees

Overview:

MQTT Transmission provides a mechanism for publishing newly added tags to the tag tree for which a Transmitter publishes on. This must be done any time new tags are added to the tag tree or tags are moved within the tag tree. It must also be done any time properties of tags are modified. This can be done manually or via a script.

Refreshing the Tag Tree for all Transmitters and Edge Nodes:

Consider the following Transmitter configuration in Transmission.

This Transmitter will look in the '[default]Edge Nodes' folder for tags to publish via MQTT. Because no Sparkplug IDs are defined in the Transmitter configuration, the first folder under the 'Edge Nodes' folder will be the Sparkplug Group ID. The second level folders will be the Sparkplug Edge Nodes IDs. So, given the following tag tree:

There are two Edge Nodes (each with their own MQTT client) with the Sparkplug Group and Edge Node IDs of:

• My Group/Edge Node 1
  • This Edge Node has a single Sparkplug Device called 'PLC 1'
• My Group/Edge Node 2
  • This Edge Node has a single Sparkplug Device called 'PLC 2'

Browse to the MQTT Transmission '[MQTT Transmission]Transmission Control/Refresh' tag as shown below and write a value of true to it by clicking the boolean checkbox:

Now browse to the MQTT Engine tag provider and verify the tags for both Edge Nodes have arrived as shown below.

Browse back to the default tag provider and create a new memory tag under 'PLC 1' called 'Tag 3' as shown below:

Now browse back to the MQTT Transmission tag provider and you will see the 'Refresh Required' boolean tag now shows 'true'. This is because a new tag was added which means a new BIRTH sequence must be published for consumers of the messages (such as MQTT Engine) so they can pick up the tags.

At this point writing a true to the tag '[MQTT Transmission]Transmission Control/Refresh' must be done before the new tag will be picked up by MQTT Engine.

After doing so, the new tag appears in MQTT Engine as shown below.

Refreshing the Tag Tree for a Single Edge Node: