Keyboard scanner

[BJ]

Beszedes Arpad wrote:
> 
> Hallgeir Helland wrote:
> >
> > Hi folks,
> >
> > I've now designed a microcontroller based keyboard scanner
> > based on the diode matrix idea (thanks Paul!) but I have
> > this one thought....
> >
> > I'm using the Motorola 68HC705 µC and it has TTL architecture
> > (or so my teacher sez) and since I'll be using diodes on
> > each switch, there will be a voltage drop of about 0.6 V
> > on the input of the µC, right? Will it matter having 4.3 V
> > on the input instead of 5 V ?  Should I use buffers or
> > something?
> >
> > BTW: I'm using Protel '98 (trial version) for PCB design. OK.
> >
> 
> I've tried Protel98 also, but I'm not satisfied with it: I've been using
> autotrax for ages and it was more than good (not a single problem with
> it in >5 years). But when I first started Protel98 (importing my old
> autotrax design) it crashed, and again, and again....
> And there were other situations too when completely with no reason it
> simply crashed.
> Of course there are a lot of new features and a nice (maybe too nice)
> user interface, but I have a feeling that I'd be more satisfied with a
> smaller set of options but with a REALLY reliable and stabile tool.
> That's my experience and opinion.
> 
> Regards,
>   Arpad.

One recomendation, go backwards to the PCB2,8 version if you 
must use Protel tools! Its stable and dont crash!

The 98 is not recomended among professional cadd people,
it is to unstable as you have experienced!

BJ