====MQTT Event Notifications====

This type of [[start|distribution]] sends incoming data to your MQTT server, with one topic per property. 

However, rather than being a live stream of updates, these topics are only sent updates when a //significant change// happens.

For **discrete** values (on/off signals, statuses, text values etc.), messages will be sent with any change. This reflects machines turning on/off, doors closing etc.

For **analogue** values (measurements), these messages will only be sent if the value exceeds the //standard deviation// by more than a given amount - which defaluts to 3x. 

As an alternative that pushes **all** data via MQTT with one message per point of data, see [[mqtt|mqtt]].

===Type Name===

The type name to use in your configuration is **mqttev** (MQTT EVent based).

===Configuration===

The following configuration options are accepted...

^Name^Notes^Purpose^
|hostname|Required|The DNS name or IP of your MQTT server|
|port|Default 1883|The port number used to communicate to the MQTT server|
|topic|Required|The base topic to publish to|
|username||The username to connect to the MQTT server|
|password||The password to connect to the MQTT server|
|bufferlen|5|The number of samples to record when calculating Standard Deviation|
|threshold|3|The number of times greater than the standard deviation the difference has to be/|

The //threshold// parameter allows you to adjust the sensitivity of the tests. The larger the number, the less sensitive the tests will be and the fewer events will be sent.

===Suggestions===

We usually suggest using the **fullpath** option in your [[configuring_live_data_distribution|configuration]] to replicate your ARDI asset hierarchy in your MQTT system. But this is not a requirement.

===Example Payload===

<code>
increased:22.5
</code>

or 

<code>
changed:5
</code>