How to determine USB version on Linux

Plug your device in, then see syslog:

$ tail -n 2 /var/log/syslog
Dec 22 17:25:14 localhost kernel: [73348.931267] **usb 2-3** : new **high speed** USB device using ehci_hcd and address 13
 Dec 22 17:25:14 localhost kernel: [73349.084555] usb 2-3: configuration #1 chosen from 3 choices

Note the device bus id there: usb 2-3. Now get the version:

$ cat /sys/bus/usb/devices/2-3/version
2.00