Hi,
normally you don't talk to a bus such as USB, you talk to devices attached to the bus.
Also normally the USB device comes with a driver, hence your app communicates with the driver in accordance with the driver's documentation.
If you happen to build your own USB device you should consider writing your own device driver, not a beginners job. And you may be interested in
this stuff[
^] which I haven't looked into yet.
:)