The program I'm using (gpio-event) claims to account for debounce in
software. The problem isn't an unclean triggering when the user
actually pushes the button, but that I get rising and falling events
even when the button isn't pressed. I'll have to take another look but
I think the resistor idea may be sufficient.
Nice to hear from you. Thanks for the help.
From: Mark Corner [mailto:mcorner@...]=20
Sent: Friday, December 08, 2006 7:37 PM
To: Silva, Russell
Subject: Re: [Gumstix-users] Noisy pushbutton
I saw your note on the list. You need a "debouncing circuit". The
pullups will work, but a small cap will help as well. Gooel will find
you what you need.
On 12/8/06 4:56 PM, "Silva, Russell" <rsilva@...> wrote:
I've connected a pushbutton to LDD0 (GPIO58) and the adjacent GND on my
breakout board. I use gpio-event to detect falling edges.
My problem is that the connections appear to be very sensitive and
noisy, triggering even when the button is not depressed. I imagine I've
committed some fundamental error but my electrical engineering skills
are very poor and I'm not sure what to do.
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From: Dave Hylands <dhylands@gm...> - 2006-12-11 14:44:27
> The program I'm using (gpio-event) claims to account for debounce in
> software. The problem isn't an unclean triggering when the user actually
> pushes the button, but that I get rising and falling events even when the
> button isn't pressed. I'll have to take another look but I think the
> resistor idea may be sufficient.
Yeah. Without the resistor, when the switch is open, you've
effectively got an unconnected input. In CMOS, unconnected inputs have
a nasty tendency of following pins that they're near (or traces that
they're near). This is sometimes referred to as capacative coupling.
So if you're just using a SPST switch the resistor is a MUST.
Vancouver, BC, Canada