On Thu, Jul 21, 2011 at 9:50 AM, Uffe Jakobsen <u...@uffe.org> wrote:
> > > 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 >> 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 _______________________________________________ email@example.com mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-usb To unsubscribe, send any mail to "freebsd-usb-unsubscr...@freebsd.org"