If you've already rolled your own printer control code then you can pass the commands straight through to the printer by setting up the printer using the "Generic / Text" printer driver on the USB port. That driver will not re-interpret the control codes and try to print them, but it will just hand them off to the printer as-is.
Then the USB port can be used just like any other printer.
This approach worked for me on a POS system that I developed.
