OpenTherm in LabView

[muharani2014]

How can I interface with a boiler controller or thermostat that use OpenTherm protocol in Labview? What hardware do I need other than, say, a USB multifunction DAQ X series?

[mikeporter]

Have you read the spec? The signalling appears to use Manchester encoding so I would look at digital io with external signal conditioning. From a quick look at the spec it appears that it uses both current level and voltage signalling.

Does someone make a serial io card/board that does Manchester encoding?

Mike...

[rolfk]

The signaling is a little bit complex in that it uses both voltages and currents. Not something easily done with a normal DAQ card. There has been a project in Elektor some time ago that created a simple circuit to create OpenTherm compatible signaling from a serial port. You still have to implement the manchester encoding but at least the electrical signaling interface is taken care of. I believe it is still possible to order the article that contains the description for this project from them.

Another DIY project is the OpenTherm Gateway project, but you can also buy the print from them.