Then comes the trick! At a certain point, the bytes are encoded with XOR (Exclusive Or) 0xAA. The protocol is 1200 baud, 8 data bits, 2 stop bits and even parity. There was one more mistake in programming. Please forget the telegrams mentioned above. The KM bus is now most likely the M-BUS, because I have the first useful results. Do you have a vitotrol ?Ībout the status message (21 bytes), I found some time ago some decoding information : I believe the 40 bytes telegram is about the program schedule (heater and hot water). This implies that we can’t see the vitotrol and the internal extension (the only slave I believe, in my case) replying to ping requests.
Using KM bus, the slaves on the bus will never “see” (receive) the telegrams sent by the other slaves (as slave to master communication is done through current modulation).
I decided to look back at this, and I figured out I was wrong in my previous reply.
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