I'm having trouble getting a definitive circuit for the auto reset, for example looking at the schematics for several boards...
Mega - Uses DTR through a cap but has a solder bridge that appears to do nothing, also uses RTS through a resistor to RST. Why both and what's with the bridge in parallel with a bare wire?
Duemilanove - same as mega.
Sanguino - Uses RTS through a cap and jumper. This makes sense but is way different to the official circuits.