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Intro

My DIY Home Automation system is powerd by a WAGO PLC 750-881. This PLC has ethernet and is wired to my Home network. I wanted to start tracking the usage of lights and powerusage. During my research I stumbled accross the IBM MQTT protocol. Being a simple protocol and being flexible enough to do what I wanted, I planned to make my PLC support MQTT. A little bit of Googling showed that there was not off the shelf library available. So I read the specs and started my first advanced PLC program.

Roadmap

Ofcourse this first version is rather simple and is just enough to do the bare minimum. It supports the following messages:

• CONNECT
  • Only a QoS of 0 is supported.
  • Username and password are supported.
• CONNACK
• PUBLISH
• PINGREQ Fixed to 10s
• PINGRESP

In the future I want to implement QoS 1 en 2 and enable subscribing to topics.

#Usage

mqttClient(
xPublish := xPublish, (* I/O variable to publish to a TOPIC *)
xSubscribe := xSubscribe,  (* NOT SUPPORTED, but must be here for I/O *)
sIP:='192.168.10.10', (* IP of the MQTT Broker *)
wPortNumber:=1883,  (* PORT of the MQTT Broker *)
(* AUTH: When no authentication is needed, leave the following fields Blank *)
sUsername:='user',  (* Username to connect with the MQTT Broker *)
sPassword:='pass' (* password to connect with the MQTT Broker *)
);  


mqttClient.sTopic := 'home/lights/kitchen';
mqttClient.sPayload := BOOL_TO_STRING('FALSE');
xPublish := TRUE;