[Nut-upsuser] [Nut-upsdev] Mustek PowerMust 1000AV USB feedbacks

Arjen de Korte nut+users at de-korte.org
Sun Aug 12 16:01:11 UTC 2007

>> This value may be entirely bogus, maybe your UPS doesn't have an
>> internal temperature sensor (or it is broken). From the debug data, this
>> is the actual value read from the UPS, so there is nothing we can do
>> about that.
> Yes it it definitely broken. It has never changed since i'm using that
> power supply.

Then this value is probably hardcoded in the UPS. I would expect the value
to be way off the scale (some bizarre value) if it would be broken. Maybe
the company that made the device for Mustek was too cheap to spend a few
cents on a functional temperature sensing circuit. This speaks volumes for
the rest of the hardware... :-(


>> The battery charge is calculated by the megatec driver based on the
>> battery voltage, it's not a value from the UPS. This is not a very
>> accurate way of determining the battery charge and will result in a
>> highly non-linear transfer function. Don't count on it to be accurate,
>> it isn't.
> Just to make the returned values more consistent with the upsc output,
> it would be great to have an emulated "remaining time" feature as well :)

Please not, we're already getting enough questions about the inaccuracies
of this value, that's not going to improve if we add a countdown timer
that may jump several seconds (in both directions) between queries.
Personally, I feel that we (= the NUT developers) should only translate
parameters received from the UPS to internal NUT representation, but due
to popular demand, sometimes driver authors go a long way trying to
calculate missing values.

>> If realistic values for battery charge and runtime are important to you,
>> you're better of with a more sophisticated UPS.
> It is just to avoid breakage during a power failure, no more :)

In that case, the UPS is probably fine for your application.

>> With regards to the shutdown problems, try if this works through the
>> serial interface. The megatec_usb driver is very new, so this may indeed
>> be a bug. It could also be that your UPS simply doesn't respond to this
>> command. The best way to verify this, is by trying the same through the
>> serial interface and post the results here.
> Actually, I have tested the power supply with the serial interface and
> it stopped as expected when upsmon sent an fsd (however it doesn't wake
> up again like the mge).

That is bad. :-(

> IMO, it is like a bug in the serial to usb driver.

That could be. The megatec_usb driver is a fairly recent development, so
it may suffer from some problems still. Another thing is that it requires
that the USB stack is still available at the time of shutting down, which
may not be the case. If the serial interface is a problem for you (because
your server doesn't have a free RS-232 interface), another option would be
to use an external serial-to-USB converter that is recognized by the OS.

Best regards, Arjen

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