MQTT_Subscribe block

Short summary

Name	MQTT_Subscribe
→POU type	→function
Category	more system blocks, MQTT
Graphical interface
Available since	version 1.28.0 (for Neuron Power Engineer) and version 2.3.1301 of the →runtime system – initial variant version 1.108.0 (for Neuron Power Engineer) and version 3.18.0 of the →runtime system – enhancement: data type STRING for existing input topic (instead of STRING[255]); data type MQTT_RC for output rc (instead of DINT)  This block is supported for →Raspberry Pi.

Functionality

The block subscribes to a topic for an established connection determined by a connection handle.

 The data is transferred by means of an already existing MQTT broker (see "Preparing/Realizing data transfer via MQTT").

Inputs, outputs, return value

	Identifier	→Data type	Description
Inputs:	ch	DINT	connection handler (as obtained by the MQTT_Connect block)
	topic	STRING	topic to subscribe to
Outputs:	rc	MQTT_RC	return code of involved MQTT functions as specified in data type MQTT_RC

Input EN and output ENO are available when →calling the block. See "Execution control: EN, ENO" for information on input EN and output ENO.

See:

• "Blocks for safe logic" whether this block is supported for developing safety-relevant applications.

• "Highlighting safe logic in the FBD-editor" for the effects when using the block as a block for safe logic.

Example for usage within ST-editor

See "MQTT_Unsubscribe block".

When creating your application within the ST-editor, enter a call of a block by typing the text as requested by the syntax or use Content Assist.