Creative USB interface
The creative USB interface is a simple bootloader thats initially loaded onto a 18f4550 PIC which allows the PIC to be reprogrammed there on out via USB directly to the chip. An outside PIC programmer is required once for the initial burning of the PIC but from there on out it can be done using the USB connector. The USB connection to the computer also allows programing of HID's which can move data to and from the computer. It really is a high speed link between the computer and whatever devices you hook the PIC up to.
from the CUSB site:
1. Write your program using your favorite text editor or the editor included in Microchip's MPLAB. Generally, you'll write your program in C. In exceptional cases, you may write your program in assembly code.
2. Compile your program. Normally, you'll use the MPLAB environment to invoke the C18 C-compiler. C18 will compile your C code into a .hex file. If you've written assembly code, MPLAB will assemble your .asm file into a .hex file.
3. Program the PIC18F4550 by downloading the .hex file via bootloader using the PDFSUSB.EXE program (located at C:\CUI\Pdfsusb\ by default). In order to get the CUI to show up in the PDFSUSB.EXE menu, you must reset your board while holding down the "program" button. NOTE: if this is the first time you have ever programmed a newly built CUI board, you must first burn the bootloader code into the PIC. Section 5 details this one-time procedure that requires the use of a PIC programmer such as the ICD2.
4. Run your application. This is as simple as hitting the "execute" button in PDFSUSB.EXE, or hitting the reset button on your board, and watching it run. If it runs okay, hooray! If it doesn't, go to the next step.
5. (Oops.) Debug your application. Section 4 offers tips and techniques for debugging.