Note that portmon can only sniff serial ports and modems (ie what the
USB driver exposes the device as). Chances are this is fine. There
are various USB sniff programs out there, but you need a very good
understanding of USB first.

There are various flavours of a program named Snoopy out there.
The script experiments/snoopyanalyse.py will convert Snoopy
output into something more useful.

Roger