MQTT Binding need to be installed. I have done this with the paper UI in the binding tab; OH needs to publish message, so MQTT Actions is installed at the actions tab.
From that moment it is possible to send and receive mqtt messages with OH. mqtt has been developed to transfer data in a most effective way. See the net for additional info on MQTT.
Items data looks like this:
Switch gar "Garage" <garage> (Lights) {mqtt=">[hoco:home:command:ON:gar1],>[hoco:home:command:OFF:gar0],<[hoco:home:state:ON:garst1],<[hoco:home:state:OFF:garst0]"}
The gar0 and gar1 is collected and processed by the python program.
The garst0 and garst1 is the status comming from python.
The “>” sends a message; the “<” receives a message
Probably I will stay with the mqtt setup, as the pcf8574 is only one item part off the i²c circuits available. Python gives the possibility to use other i²c circuits, more complex units, such as volume and equalizer circuits and led/display controllers and many more…
Rik