adc_avr.c

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#include "adc_avr.h"

#include "cfg/cfg_adc.h"
#include "cfg/cfg_proc.h"
#include "cfg/cfg_signal.h"
#include <cfg/macros.h>
#include <cfg/compiler.h>

#include <cpu/irq.h> // IRQ_ASSERT_ENABLED()

#include <drv/adc.h>

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

#define ADC_AVR_AREF   0
#define ADC_AVR_AVCC   1
#define ADC_AVR_INT256 2
/* \} */

#if CONFIG_KERN
    #include <cfg/module.h>
    #include <kern/proc.h>
    #include <kern/signal.h>


    #if !CONFIG_KERN_SIGNALS
        #error Signals must be active to use the ADC with kernel
    #endif

    /* Signal adc convertion end */
    #define SIG_ADC_COMPLETE SIG_SINGLE

    /* ADC waiting process */
    static struct Process *adc_process;

    ISR(ADC_vect)
    {
        sig_post(adc_process, SIG_ADC_COMPLETE);
    }
#endif /* CONFIG_KERN */

void adc_hw_select_ch(uint8_t ch)
{
    /* Set to 0 all mux registers */
    #if CPU_AVR_ATMEGA8 || CPU_AVR_ATMEGA328P || CPU_AVR_ATMEGA168
        ADMUX &= ~(BV(MUX3) | BV(MUX2) | BV(MUX1) | BV(MUX0));
    #elif CPU_AVR_ATMEGA32 || CPU_AVR_ATMEGA64 || CPU_AVR_ATMEGA128 || CPU_AVR_ATMEGA1281
        ADMUX &= ~(BV(MUX4) | BV(MUX3) | BV(MUX2) | BV(MUX1) | BV(MUX0));
    #else
        #error Unknown CPU
    #endif

    /* Select channel, only first 8 channel modes are supported for now */
    ADMUX |= (ch & 0x07);
}


uint16_t adc_hw_read(void)
{
    // Ensure another convertion is not running.
    ASSERT(!(ADCSRA & BV(ADSC)));

    // Start convertion
    ADCSRA |= BV(ADSC);

    #if CONFIG_KERN
        // Ensure IRQs enabled.
        IRQ_ASSERT_ENABLED();
        adc_process = proc_current();
        sig_wait(SIG_ADC_COMPLETE);
    #else
        //Wait in polling until is done
        while (ADCSRA & BV(ADSC)) ;
    #endif

    return(ADC);
}

void adc_hw_init(void)
{
    /*
     * Select channel 0 as default,
     * result right adjusted.
     */
    ADMUX = 0;

    #if CONFIG_ADC_AVR_REF == ADC_AVR_AREF
        /* External voltage at AREF as analog ref source */
        /* None */
    #elif CONFIG_ADC_AVR_REF == ADC_AVR_AVCC
        /* AVCC as analog ref source */
        ADMUX |= BV(REFS0);
    #elif CONFIG_ADC_AVR_REF == ADC_AVR_INT256
        /* Internal 2.56V as ref source */
        ADMUX |= BV(REFS1) | BV(REFS0);
    #else
        #error Unsupported ADC ref value.
    #endif

    #if defined(ADCSRB)
    /* Disable Auto trigger source: ADC in Free running mode. */
    ADCSRB = 0;
    #endif

    /* Enable ADC, disable autotrigger mode. */
    ADCSRA = BV(ADEN);

    #if CONFIG_KERN
        MOD_CHECK(proc);
        ADCSRA |= BV(ADIE);
    #endif

    /* Set convertion frequency */
    #if CONFIG_ADC_AVR_DIVISOR == 2
        ADCSRA |= BV(ADPS0);
    #elif CONFIG_ADC_AVR_DIVISOR == 4
        ADCSRA |= BV(ADPS1);
    #elif CONFIG_ADC_AVR_DIVISOR == 8
        ADCSRA |= BV(ADPS1) | BV(ADPS0);
    #elif CONFIG_ADC_AVR_DIVISOR == 16
        ADCSRA |= BV(ADPS2);
    #elif CONFIG_ADC_AVR_DIVISOR == 32
        ADCSRA |= BV(ADPS2) | BV(ADPS0);
    #elif CONFIG_ADC_AVR_DIVISOR == 64
        ADCSRA |= BV(ADPS2) | BV(ADPS1);
    #elif CONFIG_ADC_AVR_DIVISOR == 128
        ADCSRA |= BV(ADPS2) | BV(ADPS1) | BV(ADPS0);
    #else
        #error Unsupported ADC prescaler value.
    #endif

    /* Start a convertion to init ADC hw */
    adc_hw_read();
}