AVR-Chat

hi there 

if the dongle you want to developed will interfaced to the USB, the 
chip FT245R or FT232R will help you since these chips have a serial 
number burned on it (no two chips have the same serial number) which 
you can use to verify using the AVR controller 
note that these chips are not controllers they just convert the USB 
interface to 12-pin parallel interface (FT245R) or to the Serial Port 
Interface (FT232R) 

for more information check 
www.ftdichip.com       [Chip Manufacturer]
www.dlpdesign.com      [USB Products]

Good Luck 
Mohamed Sadek