After spending a few hours reviewing the source code and commenting it so that it will hopefully make some sense, I'm happy to submit the finished source code.

Included in the submitted tgz is a Makefile, and all the source code for assembly. The assembler used is gpasm, which is available in GPUTILS. It also has a line for programming my MCU via the PICKIT2 programmer, using the pk2cmd tool.

To build, the ubiquitous "make all" should work as long as GPUTILS are installed.

Making this code work on any USB capable PIC18F chip should be a simple matter of modifying the Makefile, and adding the necessary block to usb-devices.inc. If you need any help with this, or if you've added a chip and would like to share your changes, please post your comments here on hackaday.io

Stay tuned, I'll be sharing some of the work involved in getting to this point in the days ahead.