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[Reply #105 on:]

So just out of interest, what was the "official" fix in the R3 Uno? (I know, I could just dig up and compare schematics, but I'm lazy -- sorry.)

[Reply #106 on:]

Diode was added.

[Reply #107 on:]

So, do like this?

yes, i now realize thats the best solution. if shield is needed the diode can be installed on it or on the bottom of the uno. thanks for the photo, its just what i needed for those who cant read schematics or dont solder..

btw i did try leaving out the cap on some of my minimal bbb type boards. it worked in most cases but failed with some serial usb dongles. sometimes due to timing issues and other failures caused by polarity. with cap and diode it works all the time so now i mount both on the dongle. this way even a bare chip (literally zero external components) can be programmed via the ide or avrdude alone.

[Reply #108 on:]

Diode was added.

Zener to 0V, or ordinary to +5V?

[Reply #109 on:]

Cathode to +5. Anode to reset pin.
Any spikes on the reset pin are shunted to the +5V supply.
I use 1N4158.

[Reply #110 on:]

Thanks