Daniel 
Hi
I have an sd card with debian running. I wish I could use a usb drive. So
far I have copied (with dd) sd card to usb drive.
Turn on the computer and entered the u-boot menu:
MINI2440 # version
U-Boot 1.3.2-mini2440 (Oct 6 2009 - 12:51:09)
MINI2440 # usb start
(Re)start USB...
USB: scanning bus for devices...
USB device not responding, giving up (status=2)
1 USB Device(s) found
scanning bus for storage devices... 0 Storage Device(s) found
MINI2440 #
Any ideas?