From what I have read, OpenTherm is an interface standard for connecting smart thermostats that can tell a boiler outflow temperature to boilers that can respond accordingly. I have seen some projects for making an OpenTherm compatible smart thermostat to an OpenTherm interface, but I have failed to find the OpenTherm interface specification. Seems you have to be a member of the OpenTherm consortium to obtain that, which means, being a manufacturer.
I believe I have also figured out that there are two flavours of OpenTherm - OT/+ and OT/-. OT/- is some sort of PCM coding and, I think OT/+ is some sort of digital bit stream.
Can anyone confirm or dispute my conclusions?
Can anyone provide me with a copy of or a link to the OpenTherm interface specification, please?