On 2011-07-21 14:55, Mehmet Erol Sanliturk wrote:

On Thu, Jul 21, 2011 at 7:12 AM, Uffe Jakobsen <u...@uffe.org
<mailto:u...@uffe.org>> wrote:

    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 .

Hi Mehmet,

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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