Olin Lathrop wrote:
>
> > 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.
>
> That's going to be tough because RS-485 is a multidrop bus, not a ring.  You
> could implement a ring from individual point to point RS-232 connections,
> but that would require two UARTs per node.

Maybe "token ring" isn't the right term for what I'm thinking cause I seem to
have sent everybody on a different path. "Token ring", as I understand it, isn't
a network topology, its a communications protocol. We use it on several of our
robots (www.ssl.umd.edu) and I think it was used for PC's back in the heyday of
coax cabled LAN's, but that was before my time.

The system I'm refering to, whatever its called, involves a series of nodes on a
multi-drop broadcast network that need to communicate peer-peer. A node can only
communicate when it has the "token", when its done with the network it gives the
token to another node which then either uses the network or passes the token on
to the next node. The token tends to move around the network in a ring, hence
"token ring". Obviously there are some problems with this system, but it works
for simple networks.

> RS-485 isn't suited for this.  If you want arbitrary peer to peer
> communication with no master, look into CAN.  It is designed for exactly
> this kind of operation.

I've thought about CAN, but haven't looked into it much. Maybe I'll take a
second look. Thanks.

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