I don't think it is related to supplying issue. At least I don't see any difference in communication errors when supplying the Raspberry and USB hub separately.   Forcing the USB to slower full-speed seems to be an improvement, by adding dwc_otg.speed=1 to /boot/cmdline.txt http://www.raspberrypi.org/forums/viewtopic.php?f=44&t=8010&start=75   Most of the cases it does succeed to open the device, configure the AWG and perform an acquisition. pi@raspberrypi ~ $ python AnalogOutIn.p