I'd like to add a USB connection to my current project so a computer and the project can send data to each other via the serial port. I think I can use the FT232, basically cloning the Duemilanove schematic:http://arduino.cc/en/uploads/Main/arduino-duemilanove-schematic.pdf
My circuit needs more power than USB can provide (3a) so it will always be connected to an external (regulated) source, but I'm not sure I understand how to keep the USB power separated from the circuit power, so they can't damage each other etc.
It looks like the MC33269D is the voltage regulator because a regular Arduino can run from 5-12 volts? I don't think I need that because the external power's already regulated to 5v 3a.
It looks like the LM358D and NDT2955 control powering the circuit from USB or external power? If I know I'll never power the circuit from USB can I just leave all that out?
Is the fuse F1 just to keep the Duemilanove from drawing too much power from the USB host? I don't see one in the schematic for the Nano and since I won't be using host power can I leave it out?
Finally is there anything else I need to do to protect the host from the circuit, and vise-versa?
As always, thanks for your help.