[Nut-upsuser] Difficulty over USB with a CyberPower 800AVR and nut 2.0.3

Charles Lepple clepple at gmail.com
Fri May 19 03:36:09 UTC 2006

On 5/18/06, Woogie <woogie at gmail.com> wrote:
> It does indeed have a serial port on the UPS. I guess I'll scrounge
> about for a serial cable of some sort. I'll look through the dev
> mailing lists to see what has been done towards CyberPower USB support
> and what there is I can do. Just for clarification, will all UPSes
> which communicate over USB use the newusbhid driver, or does that
> driver only apply to some classes of USB UPSes?

There are three basic categories of USB UPSes: those that implement
the PDC (power device class) HID spec, those that just use HID as a
way to avoid writing a custom kernel-level driver in Windows, and the
other oddball schemes out there.

newhidups mostly just covers the first case. There are variations in
PDC implementations, but they are minor, and usually the HID tree is
self-explanitory to the driver writers.

The "generic" subdriver in newhidups (post-2.0.3) can distinguish
between the first two groups, but if the UPS is not PDC-compliant, it
can be an uphill battle to decipher the protocol and write a driver.
Examples of non-PDC USB UPS drivers are engergizerups and

The good news is that the non-PDC UPSes often reuse the same protocol
as their serial counterparts, just encapsulated in HID reports. Tools
such as usbsnoopy can be used to monitor the Windows control programs
to reveal the protocol.

- Charles Lepple

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