Off-Topic: question about usb-hub power

Thu Jul 21 21:29:25 UTC 2011

Hi,

I don't know which chip used in your D-Link hub Uffe, but I believe
this one made with respect of standard.

Uffe, can You do simple test with your device:
1. connect your device to active PC and check if it charging.
2. put your PC in StandBy or PowerOff mode(don't remove power cord),
reattach your device and also check if device still charging.

In both cases most devices will continue charging, but some "smart"
device in second case disable charging. (my Sony PRS-600)  

I was trying to charge my PRS with power supply with USB connector, and
reader don't start charging. So charging can start only after some
interaction between USB host and device. 

On Thu, 21 Jul 2011 12:36:29 -0400
Mehmet Erol Sanliturk <m.e.sanliturk at gmail.com> wrote:

> On Thu, Jul 21, 2011 at 9:50 AM, Uffe Jakobsen <uffe at uffe.org> wrote:
> 
> >
> >
> > On 2011-07-21 14:55, Mehmet Erol Sanliturk wrote:
> >
> >>
> >>
> >> On Thu, Jul 21, 2011 at 7:12 AM, Uffe Jakobsen <uffe at uffe.org
> >> <mailto:uffe at 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
> >>    categories:
> >>
> >>    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
> >
> >
> >
> 
> 
> 
> 
> >From the Wikipedia page
> 
> http://en.wikipedia.org/wiki/USB_hub :
> 
> "However, there are many non-compliant hubs on the market which
> announce themselves to the host as self-powered despite really being
> bus-powered ."
> 
> 
> It seems that the above unit is NOT using the power supply .
> 
> 
> One way to learn a suitable model is that one of the subscribers of
> this list knowing that will answer over time .
> 
> Personally I do not know . <-------- Forget this , please :
> 
> 
> I have a
> 
> 
> Targus 7-port Hub
> USB 2.0 Desktop Hub with a AC Adapter
> Barcode : 5 024442 863608
> ( ACH82EU )
> 
> 
> Targus Europe Ltd.
> 
> http://www.targus.com/uk/
> 
> In that site , search
> 
> 
> Targus 7-Port USB Desktop Hub
> 
> 
> 
> My unit is different than the above as model number . Therefore I can
> not say that they are exactly equivalent , but my expectation is that
> they will be similar with respect to power delivery to pins .
> 
> I have measured voltage across pins 1 and 4  just only it is
> connected to AC power line ( without any connection to any computer ,
> even USB connection cable is not plugged ) .
> 
> 
> It is giving 5.00 volts between these two pins . I checked by reverse
> measuring ( to see effect of sign ) . It is giving either 5.00 or
> -5.00 volts when measuring pins are reversed .
> 
> It is very likely that you will be able to find that model .
> 
> 
> Unfortunately , within product definition documents , mostly there is
> no any clue about your question .
> 
> 
> Another very simple test may to use a USB light .
> In computer shops it is very likely that it is possible to find
> "open" units for inspection by customers .
> 
> Attach a USB light such as
> 
> http://www.amazon.com/Portable-Flexible-Light-Laptops-Notebooks/dp/B002WI8GG8/ref=sr_1_1?ie=UTF8&qid=1311265897&sr=8-1
> 
> If it gives light , means that pins are receiving power directly from
> AC power supply .
> 
> 
> My knowledge is so much .
> 
> 
> Thank you very much .
> 
> 
> Mehmet Erol Sanliturk
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WBW
-- 
Aleksandr Rybalko <ray at ddteam.net>