MQTT Publisher

The MQTT publisher provides a northbound data interface for MQTT clients to data point values within the WinCC OA project. In contrast to the MQTT client, the publisher is no WinCC OA driver and therefore allows forwarding/publishing arbitrary data point elements directly via MQTT protocol, even if received via another protocol using e.g. S7 or IEC driver communication. No duplication of data point elements is required, and value exchange is only outwards.

The MQTT Publisher can either use Data Point Groups or CNS to define which DPE values shall be published to the broker.

Data Point Group Configuration

A predefined DP group can be used to span the MQTT topic space for publishing the data point elements. The DP group may use filters and wildcards without further restrictions. The final topic name shall directly use the fully qualified DP element name or the alias (each with system name), using MQTT separator "/". Optionally, the topic of the root node shall be used for preceding every topic.

Note: The default name of the used DpGroup is "MQTTPub". It is also possible to use another name by setting the config entry ../../cfg_doku/all_config_entries.html#mqttpub__mqttPubGroup.

CNS configuration

CNS views shall be used optionally to span the MQTT topic space. The final topic name shall directly use the CNS path of the related nodes (with system name), using MQTT separator "/". Optionally, the topic of the root node (name of the CNS view) shall be overwritten. Furthermore, a specific node shall allow overwriting the value transformation of the connection using CNS user-data.

Note: In the case of a distributed system the Publisher can export CNS Views, which are on the own or on another system.

For both examples (see images above) following structur will be pubished by the MQTT Publisher:

System1:MqttView1/production/machine/speed
System1:MqttView1/production/sum_alert
System1:MqttView1/rooms/temp1