On 2011-07-21 14:55, Mehmet Erol Sanliturk wrote:
On Thu, Jul 21, 2011 at 7:12 AM, Uffe Jakobsen <u...@uffe.org
Apologies if this is a kind of off-topic for this list - since it
does not have anything to do with FreeBSD.
The external USB-hubs (v2.0) that I've come across comes in two
Some are willing to deliver power (500mA pr. connector) even if the
hub isn't connected to a computer - and some that doesn't do this -
the hubs that I have purchased from Dlink falls into the last category.
I looking for an USB hub that is willing to deliver power without it
beeing connected to a computer in order to drive some external units
- no it is not a mobile-phone ;-)
Could anyone give me a hint what specs to look for ? - before I
actually buy another hub - the Dlink ones were not a success...
I do not know whether the above answer is correct for you or not .
Thanks for your answer - it has revealed that my initial inquiry was
quite inaccurate - my apologies for that.
I'll try to fill out the gaps.
The product I'm referring to is a Dlink DUB-H7
(http://www.dlink.com/products/?pid=149). A standard USB 2.0 hub with 7
ports that can be powered from an external power supply.
I do know how to determine if there is power on an usb connector (pins
1+4) - also I know the math involved in making sure that the hub is not
overloaded - but that it not really the issue here.
This usb-hub will (apparently like so many other usb-hubs) only apply
power to its connectors if it is connected to a computer (that is
running) - and that applies even if the external power supply is
connected to the usb-hub.
Let me give you an example:
You want to charge your mobile phone but you haven't brought the charger
itself. You've only got the micro-usb cable for the mobile phone and the
above mentioned Dlink hub - also you've got no computer at hand.
Now connecting the mobile phone to the usb-hub while the usb-hub is
connected to the external power supply will not make the mobile phone
start charging. This will only happen once you connect the "uplink" usb
cable from the usb-hub and to a computer and boot it up.
Let me add here that this has nothing to do with the complexity and
internal logic of the mobile phone mobile phone and its software - it
could be any other device that can drain its power from an usb cable.
I've previously owned an usb hub that would deliver power without beeing
connected to a running computer - but unfortunately that was lost during
relocation - and I do not remember the model/brand.
Now I realize that this functionality is a part of the usb standard -
and that leads to my original question:
It there anyway to determine this habit without unpacking and testing
every the usb-hub ?
Kind regards Uffe
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