Ok so I've thoroughly read the datasheet i think, it says that each of the
PORTB pins has a weak internal pull-up (+/-200 uA typical @ 5V). So correct
me on my math

R = 5V / 0.0002A
Pull-ups = 25Kohm  ?? did I get it right ??

So this should be ok for buttons right?

Ok so how about measuring a pulse width that varies from 1ms to 2ms with an
accuracy of 2us, is this a problem for rise and fall times?

Leslie Lowe
Hawaii, USA

>This is not entirely true.  They don't "eliminate" the need for external
>pullups.  You have to be aware of your requirements for rise/fall times.
>The weak pullups are exactly that... "weak."  If you need faster response,
>you're better off using 10K, 4.7K, or even 2.2K.  I don't know what the
>weak
>pullups are, but they're probably something in the 100K range.  Maybe the
>datasheet gives more information; I've never had to use the pullups.
>
>--Andrew
>
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