[TI-H] Re: PIC Interfacing - Web page update(hardware ?)
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[TI-H] Re: PIC Interfacing - Web page update(hardware ?)
Hi,
It is possible to use only one pin per line - on the PIC you
either put the line in input mode (to get the high-Z state)
or you put it in output mode with zero out (to get the 0 state).
This is what I did in the PIXpander (using a PIC16F84). Check
the schematic and asm code on my page.
Regards,
Sami Khawam
http://sami.ticalc.org
Carlos Becker wrote:
>
> At 17:42 23/11/2001 -0600, you wrote:
>
> >OK,
> > On your schematic you have each calc serial channel tied to two
> >separate pins on the IC. Is this really necessary? If both channels
> >are bidirectional and each pin on the chip is bidirectional then why do
> >you need to use two pins per channel. From what I understood the pins
> >on the PIC can be input or ouput. If this isn't so then I understand
> >the need for it, please correct me if I am wrong. These PICS are very
> >particular.
>
> You're right, pins are bidirectional. To change from input to output you
> have to change the trisa / trisb registers. It was the first approach I
> made, and after trying for about two weeks I thought of changing to two
> inputs and two outputs and it worked. So, in conclusion, it didn't work
> with only two pins. I tried pullups, pull- downs (if they're called like
> that) and everything I could think of. But it didn't work, and curiously it
> did when I changed to two outputs and two inputs.. strange.
> The software (pic program & ti-92+ program) were the same in both cases, so
> it's even more strange. (well, the pic code was changed to fit to two or
> four pins, just that).
>
> You could try it, it's just question of typing some code. If you make it,
> let me know.
>
> Cya
>
> Carlos Becker
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