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CVD touch - ANx Read, 16F1527

 
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gmtandi



Joined: 22 Apr 2013
Posts: 10

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CVD touch - ANx Read, 16F1527
PostPosted: Thu May 02, 2013 10:47 am     Reply with quote
Hello,

I'm trying to build a capacitive touch switch, but found a few issues when reading ADC...

When i set AN0 as sensor and AN1 as reference, it works like a charm, but when i set AN1 as sensor and AN0 as reference, the values get wrong...

AN0 = PIN_A0
AN1 = PIN_A1

My compiler version: 4.130
Clock: internal, 16mhz
Datasheet: http://ww1.microchip.com/downloads/en/DeviceDoc/41458C.pdf

Code:
#include <16F1527.h>
#device adc=16

#FUSES NOWDT                    //No Watch Dog Timer
#FUSES INTRC_IO                 //Internal RC Osc, no CLKOUT
#FUSES WDT_SW                   //No Watch Dog Timer, enabled in Software
#FUSES NOBROWNOUT               //No brownout reset
#FUSES NOLVP                    //No low voltage prgming, B3(PIC16) or B5(PIC18) used for I/O

#use delay(clock=16000000)

#define LED1 PIN_E1
#define LED2 PIN_E0
#define LED3 PIN_G0

#define TOUCH_CHANNELS 5
#define TOUCH_TIMEOUT 25

int1 status[TOUCH_CHANNELS];
int8 timeout[TOUCH_CHANNELS];
int16 counter, value;

#INT_TIMER2
void int_timer2_isr(void)
{
  for (int i = 0; i < TOUCH_CHANNELS; i++)
  {
    if (status[i] == 1)
    {
      timeout[i]++;
      if (timeout[i] >= TOUCH_TIMEOUT)
      {
        status[i] = 0;
      }
    }
  }
}


void main(void)
{
   setup_timer_2(T2_DIV_BY_64,511,4);
   enable_interrupts(GLOBAL);
   enable_interrupts(INT_TIMER2);

  counter = 0;
 
  while(true)
  {
    counter++;
    //delay_ms(1); // when printf();
   
    output_high(PIN_A0);
    set_adc_channel(sAN0); // (missing delay)
    output_low(PIN_A1);
    output_float(PIN_A1);
    set_adc_channel(sAN1); // (missing delay)
    value = read_adc();
   
    if (value> 256)
    {
      status[1] = 1;
      timeout[1] = 0;
    }
    if (status[0] == 1) { output_high(LED1); } else { output_low(LED1); }
    if (status[1] == 1) { output_high(LED2); } else { output_low(LED2); }
    if (status[2] == 1) { output_high(LED3); } else { output_low(LED3); }
    if (counter == 200) {
      //printf("%lu\n", leitura); //
      counter = 0;
    }
 }


the "value" when A0 is the sensor is almost 0 when no touch, and when A1 is the sensor, it's about 65472

The datasheet doesn't says nothing special for AN0 that is different than AN1, i think that my pads are fine, with the mTouch Demo it works fine, it must to be something with my code on CCS


Thanks,
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Thu May 02, 2013 11:46 am     Reply with quote
Your comments say "missing delay". The 16F1527 data sheet says
there should be a 5us delay after changing the A/D channel, before
you read the ADC. Why did you leave off the delay ?
gmtandi



Joined: 22 Apr 2013
Posts: 10

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PostPosted: Thu May 02, 2013 1:08 pm     Reply with quote
cause the delay was doing nothing when i was using AN0 as sensor and AN1 as reference, its working only with AN0 sensor, any other ADC is geting wrong results, i had already added a few delays and no different result got :\


that's why i added that comment, i had already tried with delays, i had changed the order a few events occurs and also didn't worked..


thanks
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