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Q: What versions of the Cirrus Link modules are compatible with which versions of Ignition8?
- A: See this page.
Q: What do each of the MQTT Modules do in simple terms?
- A: The MQTT modules for Ignition each have very specific functions. The very high level overview of each is listed below. For more detailed information see this page.
  - MQTT Distributor - A MQTT v3.1.1 compliant MQTT Server.
  - MQTT Engine - A module which acts as a MQTT to Ignition Tag Bridge. This module listens for and captures incoming MQTT messages and creates/updates Ignition tags based on those messages. In addition it listens for tag writes in Ignition and converts those to MQTT messages to send/update data and I/O on the remote MQTT devices. This module can be thought of as a tool to receive and visualize MQTT data in Ignition.
  - MQTT Transmission - An Ignition Tag to MQTT Bridge. This module listens for tag change events in Ignition and converts those to outgoing Sparkplug MQTT messages. In addition, it listens for incoming MQTT messages and updates tag values based on those incoming messages. This module can be thought of as a tool to MQTT enable Ignition Tag providers and push that data to an MQTT Server and MQTT Engine.

Q: What do I do if my UDT definition changes at the edge?
- A: MQTT Engine will ignore any received UDT definitions that share the same name as an existing definition. In order to change or update a UDT definition within MQTT Engine the old definition must first be manually deleted.
Q: If I delete and update a UDT definition in MQTT Engine will all of the existing instance's member Tags lose their custom properties and configurations (such as history)?
- A: Yes, if a UDT definition is deleted and recreated, any existing UDT instances will lose any custom properties and/or configuration.

Q: I deleted my MQTT Engine tags and lost all alarm and history configuration. How do I persist this configuration?
- A: See the existing documentation for recommendations on persisting alarm and history configuration.

Q: What does the MQTT 'Transmission Control/Refresh' in the MQTT Transmission tag provider do?
- A: This tag is used to 'refresh' the MQTT client(s) associated with MQTT Transmission. By default, any new tags added to a transmitter definition will not be published to the MQTT server. By writing to the 'Transmission Control/Refresh' tag any newly added tags will be detected and published.