Bus contention during RS-425 collisions & detection

[gcjr]

i'm familiar with polling multiple devices on an RS-485 bus.

I'm wondering if polling can be be avoided in an application where msgs are sent very infrequently (e.g.model RR speed control) by verifying that the received msg is the same as the one just just sent , and if not, queue a retransmission after a random amount of time (a ~10s msec)

at even 115200 bps, a 10 char msg will take < 1 msec. Seems the odds of 2 people sending a msg within that time is very low. Checking for a pending reception would further minimize the chance of collision.

the other question is can an rs-485 tranceiver tolerate bus contention if 2 transmitters are enabled at the same time?

[sterretje]

No practical experience.

In a MAX485 you have a transmitter and a receiver. I see no reason why the receiver at the sender side can not always be enabled and that way you can read back what goes over the bus (and find collisions).