How do I send ASCII text to printer (over USB)?
I managed to install a raw printer driver and print to it from the command line.

Using CUPS/Gutenprint's web interface at http://localhost:631/ I added a printer with device URI 


  usbtb://Generic%00%00%06/Generic%20Bulk%20Device?serial=1234567890


and selected "Raw" as the make for the printer. (Please note that the serial URI parameter corresponds to the serial number for the USB device as listed in the question!) 

I can now see the printer listed when issuing the command lpstat -p -d


  printer Generic_usbtb is idle.  enabled since Tue Jul 16 23:04:11 2013


To print the text file text.txt I write lp -d Generic_usbtb test.txt