[Nut-upsdev] Krauler UP-M500VA investigation

Peter Selinger selinger at mathstat.dal.ca
Thu Nov 16 04:44:47 CET 2006

Alexander I. Gordeev wrote:
> Hi, Peter,
> Peter Selinger wrote:
> > This is good and bad. 
> > The good news is that you have a nice Usage tree (the lines starting
> > with Path: in your debug output below), and it is easy to guess the
> > function of all the variables, as they all use standard names (except
> > the top-level 00860004, which is likely a bug - should be 00840004).
> If it is a bug, it's not caused by software.

Oh no, it's a bug in the UPS firmware, or at least a design flaw, in
the sense of "does not comply with the USB Power Device Class
specification". Both the Ablerex and the MEC have exactly the same.
> > I note that some of the usage paths seem incomplete (they end in a
> > period) - I just committed a change to SVN that might fix this
> > problem, if it is indeed a problem. ("svn update" will update your
> > sources).
> I've updated souces, here is an update of the output:

Thanks. Your Usage Tree is indeed identical to the MEC one. It is
almost identical to the one from Ablerex, except that the latter also

Path: 00860004.PowerConverter.Output.PresentStatus.00840039

Also, Ablerex returned all variables as "0" instead of timing out. 
I am not sure which is better. 

> > Also, your usage tree seems to be identical to that of two other
> > devices that we have recently seen (see the nut-upsdev and nut-upsuser
> > mailing list archives): one of them was a "MEC" and the other an
> > "Ablerex".  Since all three devices have identical (or near-identical;
> > I did not check very carefully) usage trees, their internals are
> > probably made by the same company.  So if we ever support these
> > devices, there will probably be a single subdriver servicing all three
> > of them.
> > The bad news is the many "Can't retrieve Report" messages. It looks
> > like the device doesn't want to communicate any actual values of those
> > variables. This again is consistent with what we observed in the "MEC"
> > and "Ablerex" devices - they too resisted actually being read. That is
> > of course a flagrant violation of the USB specification. We have not
> > yet been able to coax any useful information out of these devices.
> Sounds really bad. Maybe I can help to find this out?
> I have a copy of Upsilon 2000, an UPS monitoring tool. But it supports
> usb only under Windows. Maybe tracing usb io could help?
> Unfortunately I don't feel myself experienced enough. But there's no
> harm in trying.

You are welcome to knock yourself out. If you need more information on
USB in general, and HID devices in particular, the official standards
are available from 

I am afraid I can't offer much help, except perhaps with
newhidups-specific aspects.  I barely understand the USB protocol well
enough to deal with well-behaved devices. 

However, there is still the possibility that we have been missing
something really dumb.

-- Peter

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