OK, I might be totally off but how about _avoiding_ collision instead of
detecting it ?

Say all pics on the bus have ID:s #1..#5, and that also represent their priority
on the bus.
Now, for a pic to be allowed to send it must wait the number of mS that is equal
to its
ID number (2mS for pic with ID=2 in this example) AFTER the LAST detected
transmission
on the bus, before it starts to send.

This would mean that pics w high priority (low ID and therefor short wait time)
can
'sneak' in before a low priorty pic which is still waiting before send.
In principle a low priority pic can be 'starved' (no data) but if one can asume
the
high priority pics can behave and not take up all of the bus it should work.


> Olin Lathrop wrote:
> > Multi drop busses usually either have a single master like IEEE-488, IIC,
> > USB (at the broad overview level) and most RS-485 implementations (although
> > that is not part of the standard), or collision detection with random
> > backoff like ethernet, or collision detection with a priority scheme like
> > CAN.

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