> My speed requierments are very low, 500bytes/sec for the 
> whole bus would be fine for this application. I'll only need 
> to update maybe 100 nodes once per second with say a 1 byte 
> payload, 4 byte address.

some remarks:

If your communication is downstreams only a current-loop might be a nice
idea, although at 100 nodes the source voltage might be a bit high.

There is no law that the lower voltage on the bus should be 0V: I can
imagine a but with for instance signalling levels 9V and 12V.

Alternatively signalling can be in HF, which can easily be added/removed
from the power line.

100 nodes might be too large for some setups, maybe split in separate
strings, or add repeaters.

Wouter van Ooijen

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