Total power from USB

[Paul Fox]

tiago 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.

on either XO model the extra cables won't make a difference -- all the
power (1A available total) is available to any port.  does your drive
work on an XO-1?  do you have power consumption specs for your drive?

paul

 > 
 > Best regards,
 > Tiago
 > 
 > 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
 > > > _______________________________________________
 > > > Devel mailing list
 > > > 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.
 > >
 > > cheers,
 > > Sameer
 > >
 > > --
 > > Dr. Sameer Verma, Ph.D.
 > > Associate Professor, Information Systems
 > > Director, Campus Business Solutions
 > > San Francisco State University
 > > http://verma.sfsu.edu/
 > > http://cbs.sfsu.edu/
 > > http://is.sfsu.edu/
 > >
 > part 2     text/plain                 129
 > _______________________________________________
 > Devel mailing list
 > Devel at lists.laptop.org
 > http://lists.laptop.org/listinfo/devel

=---------------------
 paul fox, pgf at laptop.org