Re: Inverting RST pin (using configuration file) not working on Raspberry Pi?

[Rogier Wolff]

On Wed, Jun 02, 2021 at 10:13:09AM +0200, Martin Stejskal wrote:
> Roger, I agree that they should "survive" more, but as you correctly
> mentioned, that current will sum, so it is better to keep it low.

I just mentioned it, because if you know those diodes exist and can
handle a thing or two, you can design things that would be much more
expensive otherwise.

For example, suppose you have a mains-connected AVR in a box somewhere
doing something.... Suppose you need to know the phase of the mains
voltage... 

Using the protection diodes this is simple: Use a mains-voltage-rated
resistor (*) to an input pin. The max leakage of an input pin is 1
uA. Aim for 10uA, so you need about 22 MOhm for the resistor.

The current is well below the 10mA max for the diodes on the pin.... 

The problem with repeating that 1mA often enough is that you start
thinking that /that's/ the original number. I will not confirm or deny
that I've fallen into that trap.

        Roger. 

(*) Often two are used in series, should one fail, you still have the
other one.

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