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USB hubs?

 
 
Dave
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      01-11-2008
Are there any restrictions that come with using USB hubs. It's just
that some devices obtain their power via the USB connection. I'm
thinking that if you have a number of such devices connected they all
can't take their power from the same connection. Is this the case? And
are there any data transfer restrictions involved as well?

Many thanks for any advice,
 
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richard
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      01-11-2008
On Fri, 11 Jan 2008 09:03:03 -0800 (PST), Dave <(E-Mail Removed)>
wrote:

>Are there any restrictions that come with using USB hubs. It's just
>that some devices obtain their power via the USB connection. I'm
>thinking that if you have a number of such devices connected they all
>can't take their power from the same connection. Is this the case? And
>are there any data transfer restrictions involved as well?
>
>Many thanks for any advice,


Not really. It's a matter of what requires power and what does not.
Most of my stuff is self powered.
What limits the power usage is your power source from the computer
itself. Like any other electrical devices, plug in too many and zap!
Right now I've got like 5 or 6 devices connected with no problems.
 
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Mike Easter
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      01-11-2008
Dave wrote:
> Are there any restrictions that come with using USB hubs.


Of course.

> It's just
> that some devices obtain their power via the USB connection. I'm
> thinking that if you have a number of such devices connected they all
> can't take their power from the same connection. Is this the case? And
> are there any data transfer restrictions involved as well?


wiki sez:
" Initially, a device is only allowed to draw 100 mA. It may request
more current from the upstream device in units of 2 mA up to a maximum
of 500 mA.

" If a bus-powered hub is used, the devices downstream may only use a
total of four units - 400 mA (i.e. 2 watts) - of current. This limits
compliant bus-powered hubs to 4 ports. The host operating system
typically keeps track of the power requirements of the USB network and
may warn the computer's operator when a given segment requires more
power than is available.

"On-The-Go and Battery Charging Specification both add new powering
modes to the USB specification. The latter specification allows USB
devices to draw up to 1.5 A from hubs and hosts that follow the Battery
Charging Specification."
http://en.wikipedia.org/wiki/Usb


Also realize there are usb 1, 2, and 3 on the board.


--
Mike Easter

 
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olfart
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      01-11-2008

"Dave" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> Are there any restrictions that come with using USB hubs. It's just
> that some devices obtain their power via the USB connection. I'm
> thinking that if you have a number of such devices connected they all
> can't take their power from the same connection. Is this the case? And
> are there any data transfer restrictions involved as well?
>
> Many thanks for any advice,


the power from the computer USB to the Hub is limited. Get a powered Hub
which has it's own power supply and you will be OK


 
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sdlomi2
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      01-14-2008

"olfart" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
>
> "Dave" <(E-Mail Removed)> wrote in message
> news:(E-Mail Removed)...
>> Are there any restrictions that come with using USB hubs. It's just
>> that some devices obtain their power via the USB connection. I'm
>> thinking that if you have a number of such devices connected they all
>> can't take their power from the same connection. Is this the case? And
>> are there any data transfer restrictions involved as well?
>>
>> Many thanks for any advice,

>
> the power from the computer USB to the Hub is limited. Get a powered Hub
> which has it's own power supply and you will be OK
>

For devices requiring marginally more power, I think??? I've seen usb
splitter-cables--a y-cable with 2 ends that plug into 2 computer usb
ports(in this case, 1 hub port and 1 computer port) and then its 3rd end
plugs into the device. s


 
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