Re: USV control with repeated USB disconnects

From: Hans Petter Selasky <>
Date: Tue, 27 Sep 2022 17:41:29 UTC
On 9/27/22 17:45, Frank Behrens wrote:
> Hi,
> I could use some debugging help.
> I try to connect a CyberPower USV to my FreeBSD server, the uhid, usbhid 
> and hidbus modules are loaded and the new usb device is detected:
> Sep 27 17:10:51 <kern.crit> kernel: ugen6.2: <CPS VP1200ELCD> at usbus6
> But after some seconds the device is automatically disconnected and the 
> detection process starts again:
> Sep 27 17:10:59 <kern.crit> kernel: ugen6.2: <CPS VP1200ELCD> at usbus6 
> (disconnected)
> Sep 27 17:11:03 <kern.crit> kernel: ugen6.2: <CPS VP1200ELCD> at usbus6
> Sep 27 17:11:11 <kern.crit> kernel: ugen6.2: <CPS VP1200ELCD> at usbus6 
> (disconnected)
> A change of cable and usb port did not help. I switched usb debugging 
> on, but could not find any hint, that could guide me. I collected a lot 
> of debugging information, an usb dump file
> and system information in 
> Does one of the specialists see what the problem is? Is there any 
> additional information I should provide?


If you compile a kernel with "options USB_DEBUG" then enable:

sysctl hw.usb.uhub.debug=15

This will show if the device initiates the disconnect or not.

Dumping the USB device and configuration descriptors may also be useful.

FreeBSD has some logic to reject USB autoinstall CD's. I'm not sure if 
this is the cause.

Please also read this thread:

"Flickering connection to UPS (again, but now I'm sure it is Ok under 
Windows)" on this list.