All the complex computation are handled by the Personal Computer (having ubuntu os) . This can decrease cost by large extends as We all have personal computer .
So , how we communicate between Personal computer and Embedded System (i.e Avr , Arduino).
Communication Protocol available in PC
Communication Protocol available for Embeded System
Current Arduino boards are programmed via Universal Serial Bus (USB), implemented using USB-to-serial adapter chips such as the FTDI FT232