James,
I faced the same problem with a surplus UPS I got.  Take a look at the Linux
UPS Howto on metalab.unc.edu/mdw/HOWTO/UPS-HOWTO.html . They have a section
on different interface types.  Although my UPS was not listed, given a
little testing and looking at the different diagrams, I was able to come up
with what it was doing pretty quickly.  The HOWTO also has a section on
cable building and of course how to get it working under linux.
John
>
> I'm trying to figure out the interface pinout for a uninteruptible
> power supply (UPS) that I have.  The unit came with no documentation,
> and no interface cable, and I suspect that the cable may require some
> pin remapping anyway.
>
> If you are willing to help, I've drafted a schematic of the circuit in
> the UPS attached to the DB9.  I've not gone beyond the optocouplers; I
> got rapidly lost.  I've also taken a few snapshots of the PCB.
>
>         <http://quozl.netrek.org/p600v/> (220k of images)
>
> The UPS is straight analog; there are no digital components on the
> PCB, no crystals, no microcontrollers (sadly), just bog standard
> things like LM339's.  I suspect therefore that the signalling from the
> UPS to the PC is just "online" and "low battery", via modem status
> lines.  But there's a twist; there is an optocoupler facing the other
> direction.  I can't figure out what function it has.
>

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