http://www.microchip.com/stellent/id...param=en022625The Communication Device Class firmware is the most direct way or migrating a serial port (legacy) application to USB. In fact this firmware provides direct emulation of a serial port on PC running Windows 2K and Windows XP. As the PIC18F4550 is attached to the PC, a virtual COMx port is created. All PC software using a COM1-4 port will work without modifications with the virtual COM port if only at a much higher speed (approx 1Mbit/s)
PROS: free, simple to use, easy migration from serial port applications
CONS: data transfer speed limited to about 1Mbit/s, no hardware handshake emulation (not necessary)
Memory requirements: about 4K bytes
Windows drivers: no driver required (Windows 2K/XP), xxx.inf file must be supplied
rs232 emulation, or not?