I have Landys Gyr heat meter 2WR6, which has optical port for M-bus communication. I would like to periodically read its values via Arduino / RPi / NodeMCU / whatever.
From the technical manual (p. 7), it has:
Optical interface Standard, EN 1434-3 Communication Optional: M-Bus or pulse output Protocol IEC 870, 300 baud in Nb
and this datasheet says:
ULTRAHEAT 2WR6 heat meters are all equipped with an optical interface to IEC 870 as a standard, e.g. for connecting the tool PappaWin for parameter setting and diagnostics. Note: for the optical communication with the 2WR6 a n optohead with echo suppression is necessary
My model does not have any wire output. So I'm not sure if the optical interface is in fact M-Bus or not and if that IEC 870 protocol applies also to the optical interface. All references I have googled about EN 1434-3 are about wire physical layer, not optical. For optical I have googled EN 62056-21.
So the question is how this optical interface works. Will simple IR diode + IR photodetector connected to serial port work as the physical layer or more is needed? Can this be bought ready-made for a reasonable price?
Which protocol does it use? For EN 62056-21 there is openHAB binding, which I could use probably. I guess I must first send some request to the meter and it will then reply with all the data.