usbmon is a mechanism for catching information on the USB bus. This is useful for debugging some kinds of USB problems. The existing usbmon documentation is very good. A rehash of the documentation is below.
First, identify which bus number of the device you want to trace. You can find this via lsusb. e.g.
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
gives bus number 2. Then do
# modprobe usbmon
This starts the usbmon tracing. To start capturing output do
# cat /sys/kernel/debug/usb/usbmon/2u > /tmp/usbmon_out
replacing 2u with your bus number (i.e. Bus003 -> 3u, Bus008 -> 8u).
This will continue to write to the file until it is terminated. The capture steps now look like
- start capturing the usbmon output to a file - Run your tests with the USB device - stop capturing the usbmon output