The BACnet MS/TP specification recommends a maximum practical bus length of 1200m/4000ft (approx) and so does the RS-485 specification (at 38.4kbps). This seems insanely long to me in our building automation environment. Does anyone have any real data on the longest (reliable) installations out there? (Baud vs length (vs devices))
Has anyone here used/considered using the MS/TP (Multi Server/Token Passing) (used to be Master-Slave/Token Passing) from the ASHRAE 135 BACnet specification for non-building automation projects? It seems very attractive to me for systems they want to avoid a poll/response approach in favor of event/unsolicited/pub-sub/broadcast messaging. Happy to provide MS/TP protocol details if anyone interested.
Anybody familiar with this diagram of a RS-485 waveform (from Wikipedia) ?
and this diagram from the actual EIA/TIA-485 specification ( So U+ can be aligned with A )
which is then followed up with this table in the Wikipedia article
Surely this is flat-out contradictory ? (All "Lows" and "Highs" should be inverted)
