[Nut-upsdev] Krauler UP-M500VA investigation

Charles Lepple clepple at gmail.com
Thu Nov 16 14:08:07 CET 2006

On 11/16/06, Ralf Fassel <ralfixx at gmx.de> wrote:
> Note that I don't really know how all this stuff works.  The above is
> just a wild guess from an innocent bystander assuming that the device
> is asked 'what have you got', it answers '00860004.xxx' and when you
> ask it "well what is the setting of 00860004.xxx", it says "never
> heard of it".  Had you asked "00840004.xxx" it would have repsonded
> properly.

It's a good guess, but if the firmware is that broken, it will be very
difficult to guess what needs to be requested. Here's why: the HID
usage numbers (like '0084....') all map to report IDs (which are a
single byte). The usage tables are standardized, where the report IDs
are not. Also, I do not believe that user-mode Windows programs can
request reports by ID, so we have to go on the assumption that the
mapping of HID usage to report ID is correct (assuming that *someone*
can retrieve information from the UPS, and it isn't totally broken).

Note that many HID usage values can be packed into one report (in the
newhidups dump, several lines say "can't retrieve report 1").

- Charles Lepple

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