On Wed, 27 Mar 2013, David Linares wrote: > Thanks Alan. I understand, but the USB cable is plugged into an AC/DC > adaptor which can provide an output of 1A. After breaking out an USB > cable, I measured that the consumption of my board is around 130mA > (nothing connected to the hub). Then I measured with the dongle > plugged in. The real consumption of the wireless adapter is around > 210mA. The whole thing draws around 340mA Ah, okay. Then maybe this isn't a power issue. > Today, I did some further tests *without* any wireless adapter. So, I > have got the device plugged in into a main power socket via USB > (delivering up to 1A), the root hub, and the 2-port hub and nothing > else USB-wise. > The problem still happens from time to time. The 2-port hub sometimes > says it will give 500mA to its children and sometimes it gives only > 100mA (because of a corrupted hubstatus mentioned earlier). > Now that there is nothing connected on the hub, I am just wondering > how come the hub is not always detected in the same way at each boot. > Also, should it be detected as "self powered" ( > http://lxr.free-electrons.com/source/drivers/usb/core/hub.c#L1543 ) or > not ( http://lxr.free-electrons.com/source/drivers/usb/core/hub.c#L1538 > )? It sounds like the hub is rather flaky. Also, it should always describe itself as bus-powered, never as self-powered. Maybe you should try using a different kind of hub. > I forgot to mention that this issue where the hub is not detected as > "self-powered external hub" is quite hard to reproduce. It happens 1 > out of 20 tries. This could even be a loose electrical connection, silly as that seems. You never posted any usbmon results. If you could see the actual data sent by the hub when it's not working, you might get a better idea of where the problem is. > Thanks a lot Alan and everybody else. I really appreciate the support > and understanding you are providing. You're welcome. Alan Stern -- 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
