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

[Seth C. <se...@ca...>]

Hi Craig,

A more recent EDN design submission also looks to be an elegant solution.

http://www.edn.com/article/CA601828.html?pubdate=05/26/2005&text=satav

I too am working on connecting a multiswitch button to gumstix for
up/down/left/right cursor control. I am hoping the 10 exposed I/O pins on
the audiostix will work for this.  I will need just 5, so I will not need to
encode keystrokes with an separate microcontroller.

I would be interested to know what you learn about using the I/0 pins as you
progress.

Thanks, Seth


-----Original Message-----
From: gum...@li...
[mailto:gum...@li...]On Behalf Of Craig
Casey
Sent: Tuesday, June 21, 2005 2:50 AM
To: gum...@li...
Subject: Re: [Gumstix-users] Attach buttons.... ?


Dave,

Thanks! This is exactly what I need!!

Craig Casey



On 6/17/05, Dave Hylands <dhy...@gm...> wrote:
> Hi Craig,
>
> > 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.
>
> Here's a paper with a bit of background:
> http://www.edn.com/filtered/pdfs/contents/images/30603di.pdf
>
> And some other ideas:
> http://www.quickbuilder.co.uk/qb/libs/dataentry.htm
>
> Often microcontrollers scan the keypad continuously. Under linux, this
> is generally unacceptable, so you split it into two parts.
>
> 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.
>
> 2 - You then do a scan to see exactly which key is pressed.
>
> You'll need to throw in some debounce logic as well.
>
> --
> Dave Hylands
> Vancouver, BC, Canada
> http://www.DaveHylands.com/
>
>
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