USB (host mode) extremely slow?

[niebert]

Hello,
we are experimenting with an A20 SOM. It is connected via USB to a micro controller using libusb. The micro controller is limited to full speed (12Mbits) which, given all the overhead, really gives us net rates about 1.8Mbits with Windows and OSX machines. However, when connected to the A20 SOM, the USB connection is down to less than a forth!

We suspect a driver problem, of course. We use the newest image Olimex provided and compiled libusb from scratch. We have also noticed that another USB device, a Wifi stick has low data rates, maybe a related problem. We tried different combinations with and without different USB devices, the result is always the same. The only USB device type with reasonable data rates seem to be flash keys.

Any idea of what is happening or how it could be avoided?

Thanks,
-- Peter