hw_adc.c

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#include "hw/hw_adc.h"


#include <cfg/macros.h>

#include <drv/timer.h>

#include <avr/io.h>

void adc_set_active_ain(int ai)
{
    /* If number of channels is <= 4 we use the first two MUX bits */
    STATIC_ASSERT(ADC_CHANNEL_NUM <= 4);

    ai &= BV(0) | BV(1);
    ADMUX &= ~BV(MUX0);
    ADMUX &= ~BV(MUX1);
    ADMUX |= ai;
}

void adc_init(void)
{
    /* Set analog IN as input */
    DDRF &= ~(BV(PF0) | BV(PF1) | BV(PF2) | BV(PF3));

    /* Disable pull-up */
    PORTF &= ~(BV(PF0) | BV(PF1) | BV(PF2) | BV(PF3));

    ENABLE_ADC;
    adc_set_vref_avcc();
    SET_AI_ADLAR;

    /* Set the Division Factor to 128 */
    ADCSRA |= (BV(ADPS0) | BV(ADPS1) | BV(ADPS2));
}

void adc_set_vref_avcc(void)
{
    ADMUX &= ~BV(REFS1);
    ADMUX |= BV(REFS0);
}

int adc_read_ai_channel(int channel)
{
    adc_set_active_ain(channel);
    timer_udelay(STABILIZING_AI_CHANNEL_TIME);
    START_CONVERTION;

    while(ADCSRA & BV(ADSC))
    {
        /*
         * Intentionally empty loop.
         * It waits the convertion to be completed by ADC
         */
    }

    ADCSRA |= BV(ADIF);

    uint16_t val;
    val = ADCL;
    val |= (uint16_t)ADCH << 8;

    return val;
}