Re: RS485 - XPL on the wire

["g8kmh" <lehane@xxxxxxxxxxxxxxxxxxx>]

Frank,
I think there is always a case of chicken and egg! The more
information, working devices and demos available, the more it catches
on. And standards, real or de facto. For example, are we going to put
power on the 485 cable (presumably yes), 3.3V, 5V, 12V, 24V? Max
current overall? Per module? Line speed? Cable/Pin connections? If we
don't get these (and more) specced up front then we won't end up with
plug and play(!). FWIW, here's my suggestion:

+12V power (min 10V, max 15V - measured at the module)
100mA per module max (or module is self powered)
2A max per loop current limited with foldback.
32 modules max per loop (485 std)
19,200 bps (8bits,1 stop,Odd parity)Half Duplex
Connector RJ-45 (two per module)
Pin connections as Modtronix (why re-invent....)
Each module to have option of terminating resistor

There is some info on a PIC based 232<->485 buffered converter
around and PCI cards can be had at a price. There is also the one
chip MAX 3162, although not generally available (the MAX3160 is and
would do the job with another 232 chip).

I'd certainly like to push on putting the LRC into the standard for
RS232/485 comms whilst things are at an early stage.

Lehane

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