Re: [Libusb-devel] Vanishing device

[Tim R. <ti...@pr...>]

Xiaofan Chen wrote:
> On Wed, Jun 29, 2011 at 5:54 AM, joshc <act...@ho...> wrote:
>> For the most part, this works
>> well, but on occasion the device vanishes.  Which is to say that while it is
>> still connected to the USB port, the driver is unloaded from the Windows
>> Device Manager, and subsequent calls (e.g. walking through devices from
>> usb_get_busses) accordingly fail to retrieve it.  Possibly this has to do
>> with Windows or the device itself, but I thought it was worth seeing if
>> anyone had run into similar behavior from the libusb driver, and if so if
>> they had any ideas about it.

Xiaofan is right that you should ask the libusb-win32 list, but I will
point out that a Windows driver cannot ask for itself to be unloaded. 
That has to be done by the plug-and-play subsystem, in response to a
request from the USB hub driver.

That means this is a hardware issue.  I have often seen this happen with
mini-USB plugs, because they don't seat very well.  If the plug jiggles
and loses contact, you get an "unplug" event.  This can also happen if
your device is pulling more power than it claims to, as many devices do.

-- 
Tim Roberts, ti...@pr...
Providenza & Boekelheide, Inc.