Raw serial data sniffer? By USB??

This is off topic but hoped someone could point me in the right direction.

I'm trying to interface with a piece of hardward that uses a proprietary serial communication using short packets of 4 to 10 bytes for commands. I can watch it all on the scope and read the 1's and 0's manually but that takes forever.

Is there a bit of software out there that will allow me to use a couple pins in a USB port to just sniff and log the raw 1's and 0's data? I'd love to just use the +data and -data lines of a standard USB cord to clip into the Dout and Din lines as this device communicates, and have the software pick out the bits and bytes and just log them to the screen or a file.

I'd like to observe this traffic for a few hundred cycles then eventually sort the commands to find the couple bits that change during the communication to interface with them. I could do it manually on the scope but that would take days.

This seems so simple and obvious, but all the seraching I've done only comes back with USB periphrial monitoring type software that watches the actual port rather than logging raw data.

Help?

Thanks!!

http://usb-traffic-logger.qarchive.org/