Hi Daniel:
Just as an FYI and for context:
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Re our general use, we make museum and trade show exhibits that have to work (and generally do
24x7x365 for years on end. -
Re spark tests, we ground everything, puts || caps and series resistors where needed on PCB and elsewhere, etc. But if, even after that, a spark to a (grounded) metal plate in the user interface causes a hang, we simply cannot use such sensitive components, because carpeted trade shows (and many museum environments) generate 1/8" sparks to any metal surface every few minutes from tens of thousands of visitors' hands...
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Re sin wave generator:
a) I hope you noticed my diode comment, so only 0 to +10V actually going to board (well within Arduino voltage reg spec).
b) I hope it is clear that I am not expecting the system to reliably boot with 1Hz or less power-on rise time! BUT, if such an situation reliably erases program memory (which it appears to do) so that chip never again boots with any power-on rise time until it is reprogrammed, that is not OK, as that implies the chips will almost certainly become spontaneously de-programmed after just a few hundred-to-thousand power cycles in the client environment. And as you correctly pointed out in your previous post, there must be some solution because Atmel could not possibly manufacture such a chip - at least not for non-hobby use - imagine if every few thousand starts of your microwave oven the internal uP became deprogrammed!
More as I learn it,
David