Total power from USB
sverma at sfsu.edu
Sat Apr 24 15:20:01 EDT 2010
On Sat, Apr 24, 2010 at 12:04 PM, Tiago Marques <tiagomnm at gmail.com> wrote:
> I forgot to mention that's not my case since even if I plug the two USB ends
> it still can't power up.
> Best regards,
What brand/model of drive are you using?
> On Sat, Apr 24, 2010 at 7:42 PM, Sameer Verma <sverma at sfsu.edu> wrote:
>> On Sat, Apr 24, 2010 at 4:55 PM, Tiago Marques <tiagomnm at gmail.com> wrote:
>> > Hi all,
>> > I've ran into something on the 1.5 B2 I have here, which I'm in doubt if
>> > may
>> > or may not be relevant for OLPC's hardware people(it seems not), so I'm
>> > reporting it anyway.
>> > All three USB ports can deliver enough power to an USB 2.5" HDD, no
>> > problem.
>> > They cannot in the following conditions:
>> > - An extra SD card is plugged in
>> > - Another USB device is plugged in one port, even one of lower power
>> > like a
>> > flash drive. (sometimes it only takes one, sometimes it takes two, SD
>> > card
>> > power also seems to be an issue)
>> > When I try to plug in the 2.5" HDD, it doesn't have enough power to
>> > spindle
>> > at enough speed and sits there trying to start itself.
>> > When plugging in an USB device or SD card after the 2.5" HDD is already
>> > working, it suffers a loss of power and enters the restarting state.
>> > This is
>> > true if the SD card is plugged in instead(with another USB device
>> > present),
>> > which suggests me that the power is shared.
>> > No other plugged devices seem to be rendered temporarily unaccessible
>> > due to
>> > the power failure on the high power device.
>> > Best regards,
>> > Tiago
>> > _______________________________________________
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>> > Devel at lists.laptop.org
>> > http://lists.laptop.org/listinfo/devel
>> I see a similar issue with a Lacie drive on my Dell desktop. This
>> drive actually comes with a cable that has two USB cables to draw
>> power from two ports. With two ports, the platter spins without any
>> problem. With one port, the disk clicks on the Dell.
>> On a XO-1 G1G1, XO-1.5 B2 and XO-1.5 C2 I am able to power the same
>> drive via one port only both with a SD card and without a SD card. The
>> issue may very well be the USB drive power draw. I am using a LACIE
>> Design by FA Porsche http://bit.ly/9HD5uI
>> This will be important for XS-on-XO scenarios, where we would
>> piggyback the /library partition onto an external drive.
>> Dr. Sameer Verma, Ph.D.
>> Associate Professor, Information Systems
>> Director, Campus Business Solutions
>> San Francisco State University
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