Re: Reading serial port lines

From: L D Blake (not_at_any.adr)
Date: 10/14/04 

Date: Wed, 13 Oct 2004 21:18:04 -0400

On Thu, 14 Oct 2004 00:49:31 GMT, "David Reeve" <dree4456@big-pond.net.au>
wrote:

>Errr....logic thresholds have everything to do with it, this is a real world
>logic device we are talking about. Start to think about a formal engineering
>description of the situation and you'll see what I mean.

David,
In a peripheral way logic levels do matter... but I seriously doubt it's much
of an issue when you have a capacitor being discharged every time the switch
bounces closed and charging only a few millivolts while it's bounced open.

Remember, we are talking about an event that might last less than a hundredth
of a second... with perhaps a dozen or so sub-events lasting only a couple of
milliseconds each. It's not like we are putting a logic gate into long term
abiguity and, given that most IO driver chips now use schmidt inputs they are
hysterisis guarded to begin with.

I've done this hundreds of times on some pretty groddy switches and it's never
been a problem yet.

-----
Laura

http://www.start.ca/users/ldblake