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/* USB mode: USB1 or USB2; low speed, full speed or high speed */
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 snifer sniffer softwares to decode them (wireshark unix version does it fine). Snifer Sniffer software does not show low level message (ack ko ok) but does show the high level message (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.
