Auto reset circuit

Hi all,

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.

Rob

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?

I believe that the Arduino IDE software activates both the RTS and DTR signals when it wants to reset the board prior to an upload, so you can use either one. I believe the board schematic drawing will have an indication that the RTS resistor is not mounted. The 'solder bridge' is just a place where you can cut and break the auto-reset signal path, thus disabling the auto-reset feature.

Duemilanove - same as mega.

Same answer

Sanguino - Uses RTS through a cap and jumper. This makes sense but is way different to the official circuits.

Again same answer, either RTS or DTR signals can be used, no need to use both.

Lefty

Thanks Lefty.

Looking at the schematics again I see that the resister is a "100_NM", I didn't pick that to mean "Not mounted".