Using ADC without AnalogRead

Forum 2005-2010 (read only) General Frequently-Asked Questions
1

Hi, I'm trying to use ADC without AnalogRead() function.
I look into documentation and write a code which is not working and i don't know why. ;/

I selected Analog In number 2:
ADMUX=_BV(MUX1);

And i set ADC ENABLE, ADC AUTO TRIGGER ENABLE, ADC START CONVERSION and prescaler:
ADCSRA = _BV(ADEN)|_BV(ADATE)|_BV(ADSC)|_BV(ADPS2);

I'm getting all the time 5.00 value...

#include <avr/io.h>
#include <avr/signal.h>
#include <avr/interrupt.h>

#define VREF 5

volatile float result;
volatile uint8_t counter;
//volatile float measure1,measure2;

void init_adc(void)
{
ADMUX=_BV(MUX1);
ADCSRA = _BV(ADEN)|_BV(ADATE)|_BV(ADSC)|_BV(ADPS2);
}

void setup() 
{
  init_adc();
  Serial.begin(9600); 
}
void loop()
{
   result=(float)(ADCL | ADCH<<8)/1024*VREF;
   delay(1000);
   Serial.print("Analog 2 = " );
   Serial.println(result ); 
}

Can anybody help?

2

You've turned off the internal analog reference (AREF) when writing to the ADMUX register.

Try this:

ADMUX = _BV(REFS0) | _BV(MUX1);

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