> >From: Patrick J <
EraseMEinfospam_OUT
TakeThisOuTDATECH.SE>
> >Reply-To: pic microcontroller discussion list <
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> >To:
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MITVMA.MIT.EDU
> >Subject: Re: different approach to keyboard scanning?
> >Date: Thu, 10 Apr 2003 02:11:28 +0200
> >
> >
> >Use the A/D inputs of the PIC instead ?
> >(then you can define your own 0 and 1 voltage levels in software)
>
> Unfortunately, the PIC I use doesn't have A/D, and besides, the number of
> A/D inputs would be impractical.
>
> >
> >Tho I am not sure why you want to do this in the first place. It is quite
> >common
> >to read keyboards in X-Y fashion. Just not with diodes in the juncions as
> >you do.
>
> Well, to read a 3x4 keyboard you normally need 7 I/O lines (unless you add
> external chips). The way I want to do it would only need 4 lines.
>
> I also need n-key rollover, so diodes are going to be necessary at the
> junctions in any case. I just wanted to see if I could get by with just
> those diodes and a little cleverness.