Re: [Gumstix-users] Attach buttons.... ?

[Craig C. <cra...@gm...>]

Dave,

Thanks! This is exactly what I need!!

Craig Casey



On 6/17/05, Dave Hylands <dhy...@gm...> wrote:
> Hi Craig,
>=20
> > I'd like to connect an array of buttons (somewhere between 5 and 20)
> > to a gumstix connex.  Has anyone done something like this before, or
> > have any suggestions?  I'm a software guy, so I'm not sure I'd be able
> > to make a suitably quality peice of hardware to do the trick.
> > Basically, I'll need the button, when pressed to trigger an interrupt
> > ( I can write a simple driver to handle this ), or trigger some event
> > in userspace.  I'm still at the design stage, so I'm pretty flexible
> > as long as software can be made aware of the button states.
>=20
> Here's a paper with a bit of background:
> http://www.edn.com/filtered/pdfs/contents/images/30603di.pdf
>=20
> And some other ideas:
> http://www.quickbuilder.co.uk/qb/libs/dataentry.htm
>=20
> Often microcontrollers scan the keypad continuously. Under linux, this
> is generally unacceptable, so you split it into two parts.
>=20
> 1 - Detect if any key is pressed. You would normally drive all of the
> outputs low, and when no key is pressed all of the inputs are high.
> When a key is pressed, it will cause one of the inputs to go low,
> which would generally trigger an interrupt.
>=20
> 2 - You then do a scan to see exactly which key is pressed.
>=20
> You'll need to throw in some debounce logic as well.
>=20
> --
> Dave Hylands
> Vancouver, BC, Canada
> http://www.DaveHylands.com/
>=20
>=20
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