Tom H on 8 Jul 2008 19:22:20 -0700

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Re: [PLUG] USB Hub Blocks Web Cam

On Monday 07 July 2008 23:12:33 Casey Bralla wrote:
> Here's a weird one I don't understand.  Maybe somebody can help me
> understand what is going on.
> I've been goofing around with a Logitech QuckCam I got a while ago "free"
> from comcast.   It's well supported by Linux, although anything but great
> image quality.
> Anyway,the darn thing wouldn't work and I finally figured out that it was
> because it was being hooked up through a USB hub.   If I plugged it
> directly into my computer, it worked fine (well, as good as it ever would).
>  If I plugged it into a hub, it would not produce an image.
> lsusb sees it through the hub, but I couldn't get xawtv to pull an image
> from it.
> I duplicated the problem with another hub, and got the same result.  One of
> the hubs was powered, one was static.
> Can anybody explain this?  I'd like to use it through a hub (much cleaner
> wiring), but I don't even know what type of hub (if any) I should buy to
> make it work.
> Any comments, prognostications, disertations, or suggestions would be very
> much appreciated.

One caveat that most people don't know about USB, It always defaults to the 
fastest speed of the slowest device on a hub.  i.e. if you have a USB 1.x 
device plugged into a USB 2.0 hub, on a USB 2.0 port, with USB 2.0 devices 
all devices on that port will run at 1.x.

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