AVR-Chat

At 05:48 AM 31/08/2005, you wrote:
>Is it posible have trouble
>(noise) if I havent a resistor pull down?, Is best practice put a
>resistor pull down?

Yes you are asking for trouble as you input will float.
Less of a problem if you enable the internal pull up
resistors but then you will need a logic 0 to activate
the input. Make the resistor as small as possible
provided your input source can handle it, 2K-10K
are a good guide. Also if your environment is noisy
you may want to put a 100nF cap in parallel.

A small resistor in series with your input can be
helpful but you may want to limit it to about 10%
of your input resistor.

Regards

John Samperi

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