Re: [Gumstix-users] Adding a push button

[<tim...@co...>]

Hi Dave,

Yes, I agree, KISS.  Funny thing is I was just revieving
our customer schematics and they used a switch 
connected to a resistor to ground without pull up.  
I tried to tell them it would not work, but they blew 
me off suggesting software people should not be 
looking at schematics.  ;-)


Tim

BTW: Since this question has been asked more than
once on this forum, maybe we sould do a wiki page?

 -------------- Original message ----------------------
From: "Dave Hylands" <dhy...@gm...>
> Hi Tim,
> 
> > Would it be possible to have a switch connected to ground
> > via a resistor, than program the gpio as output, program it
> > high then enable the edge detect interrupt to detect a falling
> > edge?
> 
> Programming the edge detect interrupt requires that it be configured
> as an input. You really don't ever want to run the risk of having the
> pin configured as an output when the input might be connected to a
> different voltage (say the switch is closed).
> 
> Since you'd need a resistor anyways, why not just connect it up in the
> conventional manner?
> 
> Here are the two conventional ways of connecting a switch.
> 
> 3.3v ---\/\/\/\/-----+-----o/ o----- Gnd
> 
> GND ---\/\/\/\/-----+-----o/ o----- 3.3v
> 
> Where the + goes to the input.
> 
> -- 
> Dave Hylands
> Vancouver, BC, Canada
> http://www.DaveHylands.com/
> 
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