> Would using the DMX protocol be of any use here? Relatively easy to
> bit bang, and with some judicious coding, the different channels could
> be made to 'self address'  a new node.
>
> By that I mean, the chips at the node could be programmed to accept
> channel 1 (a sort of broadcast channel), the node chip would read it
> itself discover it has a non assigned node number, accepts the address
> information contained in the broadcast, updates itself, so that a
> channel 1 address won't activate it again, but the new real node
> channel now will.  Some fancy mechanism could be thunked up, to
> persuade a node to respond to channel 1 again if re-addressing became
> necessary. The drawback here would be that nodes could only be brought
> online one at a time. Other than that there are 511 channels worth of
> slaves to be had.
>
> Colin


DMX now has Remote Device Management, which includes a discovery mode to
find devices on the network. It runs at 250kbps over EIA485. I did a lot
with DMX for about 15 years, but never implemented RDM. I think it's a bit
fancier than is required here. The use of the break as a start of frame
marker in DMX is useful though. I ended doing the break in hardware. When
I was doing DMX, the UARTs in PICs could not do a break. Those that can do
it will not do a long enough break to meet the DMX spec. It's more
designed for LIN.

Harold




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