OK not really an Arduino issue but I don't know where else to ask.
The question is, can you detect a bus clash with RS485?
Every data sheet I've read shows that the drivers are push-pull or pull-push, ie they never release the bus unless disabled.
So if one was to be designing a serial protocol that depended on determining if the 1 you think you're transmitting is being overridden by a 0 from another transmitter can this be done with 485?
With CAN, LIN, open collector, diode mixing etc you can do this but not with 485 it seems.
i dont think that the detection is possible or needed
in most cases the receiver is in receive mode/disabled all the its not sending
and the protocol should handle the changing of modes
True as most (all?) 485 protocols are master/slave, but what if you are designing a peer-to-peer protocol whereby anyone can talk whenever they like. In this case you need to detect clashes.
It's possible I can't do this and I'm happy to use the other options I mentioned, it would be nice to include 485 as a physical level as well though.