I use another RT3070-based dongle with Angstrom and it works wine with
rt2870sta driver. All I had to do was to copy firmware file from my
desktop computer. If you haven't done it yet check serial console for
messages about problems with uploading firmware to the dongle. For
some reason the driver may want to load firmware for a slightly
different chipset (IIRC it wanted to load firmware for rt2870 on my
system), but making a symlink in the firmware directory was a
sufficient workaround.
[ 214.614166] rt2870sta: module is from the staging directory, the quality is unknown, you have been warned.
[ 214.669525] rtusb init —>
[ 214.672607] usbcore: registered new interface driver rt2870