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ADC problem with PIC12F683

 
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opiette



Joined: 05 Mar 2007
Posts: 1

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ADC problem with PIC12F683
PostPosted: Mon Mar 05, 2007 11:00 am     Reply with quote
I am reading incorrect values from two ADC pins on a PIC12F683. I've tried other 683s to no avail. I had this working in the cc5x compiler, but I just bought the CCS compiler for the floating point math.

AN0 = 2.3v (470)
AN3 = 0.128v (26)

Instead, I get delays of
value1 = 616 (3v)
value2 = 200 (0.98v)

What's up?

I am using version 4.024 of CCS

Here's my code:

Code:

#include "12F683.h"
#device ADC=10
#fuses INTRC, NOBROWNOUT, NOWDT, NOPROTECT, NOMCLR
#use delay(clock=8000000)

#include "math.h"

int32 get10T(int16 value1){
   float lnratio;
   float lnratio2;
   float T;

   lnratio = ( ((float)value1 *5)/(1023*0.0005*4) ) / 2000;
   lnratio = log(lnratio);
   lnratio2 = lnratio*lnratio;

   T = 3.3540154e-3;
   T += 2.5627725e-4 * lnratio;
   T += 2.0829210e-6 * lnratio2;
   T += 7.3003206e-8 * lnratio2*lnratio;
   T = 10/T;
   
   return T;
}


void main(void){
   int16 value1;
   int16 value2;
   
   int32 T1;
   int32 T2;

   //int16 oneOverDeltaT;

   delay_ms(1000);

   //----------------------------Configure ADCs
   setup_adc_ports(sAN0 | sAN3);
   setup_adc(ADC_CLOCK_INTERNAL);
   setup_comparator( NC_NC_NC_NC );

   
   while(1){

      set_adc_channel(0);
      delay_ms(100);
      value1 = read_adc();

      //T1 = get10T(value1);

      set_adc_channel(3);
      delay_ms(100);
      value2 = read_adc();

      //T2 = get10T(value2);


      //oneOverDeltaT = 1;
      //if (T2 < T1){
      //   oneOverDeltaT = (T1-T2);
      //}
      //oneOverDeltaT = 100000/oneOverDeltaT;

      output_bit(PIN_A2, 1);
      delay_ms(value1);
      output_bit(PIN_A2, 0);
      
      delay_ms(40);
      

      output_bit(PIN_A2, 1);
      delay_ms(value2);
      output_bit(PIN_A2, 0);
      
      delay_ms(80);
      
   }//while(1){
}




PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Mon Mar 05, 2007 11:25 am     Reply with quote
Quote:
#include "12F683.h"
#device ADC=10
#fuses INTRC, NOBROWNOUT, NOWDT, NOPROTECT, NOMCLR
#use delay(clock=8000000)

I can see one problem immediately. You're using AN3, which is also
the CLKOUT pin for the oscillator. You need to disable the CLKOUT
function. Change the oscillator fuse to this:

Code:
INTRC_IO
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