Is it posible to design a software to comunicate with arduino via usb, that is, to download/upload data to the board? I need to know because I was asked to design a hardware platform that is able to comunicate to pc/notebooks via usb bus.
Yes, the USB Arduino can send and receive using Serial.print and Serial.read over the USB port. Have a look a the serial communications section of the reference page for more information: Arduino - Home
If the reqirement is "real USB" the answer is no. This is because the USB port on the Arduino board is really a serial port in disguise. On the PC it will show up as a virtual serial port.
If the requirement is to communicate via a usb cable, and serial (RS232) communication is ok, then the answer is yes.
This should be good news because programming serial communication on a PC is a whole lot les difficult than programming USB communication. The downside is of course that serial communication speed is max 115 kb/s, whereas USB can be much faster.
MikMo