[kwlug-disc] USB Webcam curious behaviour

Raul Suarez rarsa at yahoo.com
Sun Aug 15 21:16:51 EDT 2010


I am not using external hubs

Raul Suarez

Technology consultant
Software, Hardware and Practices
_________________
Twitter: rarsamx
http://rarsa.blogspot.com/ 
An eclectic collection of random thoughts


--- On Sun, 8/15/10, unsolicited <unsolicited at swiz.ca> wrote:

> From: unsolicited <unsolicited at swiz.ca>
> Subject: Re: [kwlug-disc] USB Webcam curious behaviour
> To: "KWLUG discussion" <kwlug-disc at kwlug.org>
> Received: Sunday, August 15, 2010, 6:29 PM
> Does anything change if you avoid the
> use of hubs entirely?
> 
> Raul Suarez wrote, On 08/15/2010 6:04 PM:
> > Thank you,
> > 
> > That was the same advise as Bob's. I will try with a
> powered USB
> > hub to see if it makes a difference.
> > 
> > --- On Sun, 8/15/10, Chris Irwin <chris at chrisirwin.ca>
> wrote:
> > 
> >> From: Chris Irwin <chris at chrisirwin.ca>
> Subject: Re: [kwlug-disc]
> >> USB Webcam curious behaviour To: "KWLUG
> discussion"
> >> <kwlug-disc at kwlug.org>
> Received: Sunday, August 15, 2010, 2:14 PM
> >>  On Sat, 2010-08-14 at 09:20 -0700, Raul
> Suarez wrote:
> >>> When I plug just the usb webcam it works, when
> I have
> >> the wireless mouse plugged it stops working.
> >> 
> >> It could also be a power issue. From my limited
> understanding of
> >> USB (and a quick check of wikipedia appears to
> confirm this), devices can accept power in 1 to 5 units of
> 100mA, where 500mA is
> >> the maximum the bus supports. So if your camera
> required higher
> >> power (say 4 or 5 units), and your wireless mouse
> dongle required
> >> enough power to push them over the limit (say 2
> units), there
> >> would be insufficient power to run both.
> >> 
> >> http://en.wikipedia.org/wiki/Universal_Serial_Bus#Power
> >> 
> >> Usually USB ports are in pairs on the same bus. If
> you had four
> >> ports, two would probably be on a separate bus,
> which should
> >> allow you to run the devices together. Assuming it
> is a power
> >> issue.
> 
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