On Fri, 20 Aug 2010 10:50:55 -0400 (EDT), Alan Stern wrote: > On Fri, 20 Aug 2010, Dennis Nezic wrote: > > > > Do other high-speed devices work okay with the SB400 controller? > > > > Yes, i've used a bunch of usb2 devices before without any problems. > > I didn't ask about USB-2 devices; I asked about high-speed devices. > They aren't the same thing. > > > Any suggestions on how to go about debugging this? Some kind of > > usb-wire sniffer? > > That's one possibility. High-speed USB bus analyzers tend to be > expensive. The cheapest one I know of (the Beagle-480 from > Totalphase) costs $1200. > > Besides, debugging isn't helpful if it doesn't show you how to fix the > problem. I suspect it won't. > > Another thing you could do is measure the electrical impedance of the > various USB connections on the host controller and on the device, and > compare the values with what the USB-2.0 specification says. > Sometimes manufacturers don't use the right components. Well, I didn't try measuring the impedances, nor analyzing with the Beagle, but I did play around with a 10-foot usb-extension cable and a 4-port usb2 hub. It turns out that, magically, plugging in the usb card reader into only one of the four ports kindof worked -- a few XactErrs, but I was able to mount the sd-card. (I have no idea why only 1 of the 4 ports "worked" -- they look pretty symmetric and equal at first glance :S.) Things only kindof-worked via this 4-port-hub.) Adding the 10-foot extension cable (before the hub) seemed to make it "work" a bit better -- a few less XactErrs -- and I was able to transfer a few MB files over successfully (md5sum'ed). Transferring a 300MB file failed at 115MB consistently with i/o errors. (Putting the 10ft usb extension cable after the 4-port hub (farther from my laptop) made my laptop use ohci instead, which always worked.) My head hurts. -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
