[TI-H] Re: PIC Interfacing - Web page update(hardware ?)


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[TI-H] Re: PIC Interfacing - Web page update(hardware ?)




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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