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yet another adc problem...

 
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rubber



Joined: 28 May 2009
Posts: 1

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yet another adc problem...
PostPosted: Thu May 28, 2009 2:03 pm     Reply with quote
Hi!

I'm trying to read a voltage divider made by a 22k potentiometer.
pin1 of the pot goes to vcc, pin3 to vss and center pin on the pic16f877a.

I wrote this code, but seems like there's something wrong because it's not working.
Code:

#include <16F877A.h>
#device ADC=8

#include <math.h>
#include <stdlib.h>
#include <string.h>

#fuses  XT, NOWDT, PUT, NOPROTECT, NOBROWNOUT, NOLVP, WRT_50%, NOCPD

#use delay(clock=11059200)
#use rs232 (baud= 9600,xmit=PIN_B6, rcv=PIN_B7, INVERT)



int16 posicao;



void init(void)
{

setup_adc_ports( AN0 );
setup_adc(ADC_CLOCK_INTERNAL);


}


int16 converte_adc()
{

int16 adc;
     
      delay_us(10);
      set_adc_channel( 0 ); 
      adc = read_adc();
     
     
      return adc; 
}


void main(void)
{

printf("ola!!!!");
init();
printf("ola!!!!");

   while(1){
   

      //posicao=converte_adc();   
      posicao=(float)converte_adc();
      posicao=((posicao/255.0)*5.0);
      delay_us(100);             
      printf("\n posicao %ld\n\n\r",posicao);
   
}

}


Any ideas?

Thanks in advance.

RJ
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Thu May 28, 2009 2:25 pm     Reply with quote
Quote:
#fuses XT, NOWDT, PUT, NOPROTECT, NOBROWNOUT, NOLVP, WRT_50%, NOCPD

#use delay(clock=11059200)

Look in the oscillator section of the PIC data sheet. XT mode is only
recommended for crystals of 4 MHz, maximum. It doesn't have the
power to drive a faster crystal. Use HS mode.

Also, there's no reason to use write protection during development of
an A/D program.
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