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  • Knowledge of Ignition and Module installation process: Cirrus Link Module Installation
  • Have Ignition 8.0.16 or greater installed
  • Have MQTT Engine 4.0.10 or later installed

Abstract

MQTT Engine Custom Namespaces are used to provide support for generic, non Sparkplug compliant MQTT messages with string based payloads. If a custom namespace is configured MQTT Engine will convert all messages received to tags where the topic of each message will translate directly to the tag's path and the payload will be the tag's value.  

MQTT Engine supports MQTT Engine String Replacement for both MQTT Topics and Payloads for character sequences that will become part of an Ignition tag path. 

Examples

No Tag Value configured  

Let say we have a publish received on the topic "test/data/point" with value "12345".  If no Tag Value is configured, and a message is received, MQTT Engine will create a two folders "test" and "data" and a tag "point" with the value of "12345".


Tag Value Configured

If a Tag Name is configured, lets call it "payload", then MQTT Engine will convert each token in the topic to a folder and create a tag called "payload" with the value "12345"


In most cases it is useful to specify a Tag Name in order to prevent cases when a publish on a topic can overwrite a previously created tag, changing it into a folder.  Consider the case where you have the following two publishes:

1st publish on topic "one/two" will create a tag named "two" in the folder "one"

2nd publish on topic "one/two/three" will create a tag named "three" in the folder "one/two"

When the 2nd publish is received it will overwrite the first tag because "two" is now a folder instead of a tag.  This folder/tag name collision can be avoided by specifying the Tag Name to always use for tags. 

JSON Example

Let say we have a publish received on the topic "test/data/json" with value '{ "stringTag" : "12345", "folderTag" : { "intTag" : 1, "boolTag" : true } }'. MQTT Engine will create a two folders "test", "data" and "json" followed by a tag/folder structure representing the JSON value of the payload. 





Additional Resources


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