Changes
/* Sniffing USB frames */ typo
http://www.youtube.com/watch?v=fh4v4OXridc
USB is just a state machine (welcome how are you today, show me your state, show me your state, show me your state....), encoding (have to read USB manual), you can use some usb sniffer softwares software to decode them (wireshark unix version does it fine). Sniffer software does not show low level messages (ack ko ok) but does show the high level messages (ones that show that a button is pressed or not)
As it is just encoding, you can capture signals and show that they differ only when you do unpress or press a button.
