For my project that uses an RS485 network I was planning to use a token
ring system so I don't have to deal with collision detection. But I got
to thinking about it and now I'm wondering if it might be worth doing.

The solutions I've seen posted so far (and on piclist.com) all seem to
be of the bitbang variety. Since I'm using 16F877's for this project it
seems like a waste to bitbang stuff when I have a nice USART to use. Has
anybody done this yet? I'm thinking that if I leave the receiver enabled
(im using a max487) the USART should receive a byte for every byte that
it sends. If the two bytes are different a collision has occured. First
off, that sounds too simple, like something that somebody has already
thought of and rejected. Second, whats a good way of handling back-off
and retransmission?

If all the devices are set for the same back off time, or time
increment, they'll just collide again. I guess I could implement a
random number generator, but I'd rather not. Is there a good way to
handle this?

How should retransmission be handled? Obviously the sending device needs
to retransmit the lost data, but how does the receiving device know that
a collision has occured? If it doesn't know there's been a collision it
might think the corrupted data is valid.

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