/************************************************************************/
/*                                                                      */
/*  File:           avr/adc.c                                           */
/*  Description:    analog to digital conversion driver.                */
/*  Version:        1.0                                                 */
/*  Author:         Otto Mattik                                         */
/*                                                                      */
/*  (C)Copyright Otto Mattik 2014-2021.                                 */
/*                                                                      */
/*  This file is a part of 'armen' (a tiny operating system).           */
/*  'armen' is distributed under the CeCILL-V2.1 licence. For more      */
/*  details about this licence, please visit the website cecill.info    */
/*                                                                      */
/************************************************************************/

#ifndef AVR_GPIO_C
  #error "do not use this code directly, it must be included via gpio.c"
#endif

static uint8_t adc_def = 0;
static uint8_t adc_ref = 0;

/*
 * set refefence voltage for analog conversion
 *
 * it is assumed than if AVCC exist, it is connected to
 * +5V supply and AREF is decoupled by a capacitor.
 *
 *   +5V
 *    |
 *    +--> AVCC
 *
 *    +--> AREF
 *    |
 *   ---
 *  100nF
 *   ---
 *    |
 *   GND
*/
void gpio_adc_ref( uint8_t ref )
{
#ifdef CHECK_PARAM
    if( ref >= ADC_REF_VCC
  #if defined(__AVR_ATtiny841__)
    &&  ADC_REF_INT4V096
  #elif defined(__AVR_ATtiny85__) || defined(__AVR_ATtiny85V__)\
     || defined(__AVR_ATmega2560__)
    &&  ref <= ADC_REF_INT2V56
  #else /* __ATtiny1634__ || __ATmega328P__ */
    &&  ref <= ADC_REF_INT1V1
  #endif
#endif
    )
    {
#if defined(__AVR_ATtiny841__)
        if( ref == ADC_REF_VCC )
            adc_ref = 0;
        else if( ref == ADC_REF_EXT )
            adc_ref = (1<<REFS2);
        else if( ref == ADC_REF_INT1V1 )
            adc_ref = (1<<REFS0);
        else if( ref == ADC_REF_INT2V2 )
            adc_ref = (1<<REFS1);
        else
            adc_ref = (1<<REFS1) | (1<<REFS0);
#elif defined(__AVR_ATtiny85__) || defined(__AVR_ATtiny85V__)
        if( ref == ADC_REF_VCC )
            adc_ref = 0;
        else if( ref == ADC_REF_EXT )
            adc_ref = (1<<REFS0);
        else if( ref == ADC_REF_INT1V1 )
            adc_ref = (1<<REFS1);
        else
            adc_ref = (1<<REFS2) | (1<<REFS1);
#elif defined(__AVR_ATtiny1634__)
        if( ref == ADC_REF_VCC )
            adc_ref = 0;
        else if( ref == ADC_REF_EXT )
            adc_ref = (1<<REFS0);
        else
            adc_ref = (1<<REFS1);
#elif defined(__AVR_ATmega2560__)
        if( ref == ADC_REF_VCC )
            adc_ref = (1<<REFS0);
        else if( ref == ADC_REF_EXT )
            adc_ref = 0;
        else if( ref == ADC_REF_INT1V1 )
            adc_ref = (1<<REFS1);
        else
            adc_ref = (1<<REFS1) | (1<<REFS0);
#else /* __ATmega328P__ */
        if( ref == ADC_REF_VCC )
            adc_ref = (1<<REFS0);
        else if( ref == ADC_REF_EXT )
            adc_ref = 0;
        else
            adc_ref = (1<<REFS1) | (1<<REFS0);
#endif
        adc_def = 1;
    }
}

/*
 * read value of an analog gpio pin
 *
 * input:
 *  gpio        gpio pin
 * output:
 *  adc conversion if success, otherwise -1
*/
int16_t gpio_adc_get( uint8_t gpio )
{
    uint16_t value = -1;
    uint8_t prescale =
#if (FCPU <= 400000UL)
    1;
#elif (F_CPU <= 800000UL)
    2;
#elif (F_CPU <= 1600000UL)
    3;
#elif (F_CPU <= 3200000UL)
    4;
#elif (F_CPU <= 6400000UL)
    5;
#elif (F_CPU <= 12800000UL)
    6;
#else
    7;
#endif

#ifdef CHECK_PARAM
    if( gpio < (GPIO_MAX_PORT << 3) )
#endif
    {
#if defined(__AVR_ATtiny84__)
        if( gpio <= 7 )
        {
#elif defined(__AVR_ATtiny85__)
        if( gpio >= 2 && gpio <= 5 )
        {
            if( gpio == 2 || gpio == 4)
                gpio >>= 1;
            else if( gpio == 5 )
                gpio = 0;
#elif defined(__AVR_ATtiny1634__)
        if( (gpio >= 3 && gpio <= 11)
        ||  (gpio >= 16 && gpio <= 18) )
        {
            gpio -= (gpio >= 16 ? 7 : 3);
#elif defined(__AVR_ATmega328P__)
        /* ADC6 and ADC7 are not implemented */
        if( gpio >= 8 && gpio <= 13 )
        {
            gpio -= 8;
#elif defined(__AVR_ATmega2560__)
        if( gpio >= 40 && gpio <= 47 )
            gpio -= 40;
        else if( gpio >= 72 && gpio <= 79 )
            gpio -= 64;
        else
            return( value );
        {
#else
        {
#endif
            if( adc_def == 0 )
                gpio_adc_ref( ADC_REF_VCC );

#if defined(__AVR_ATtiny841__)
            ADMUXA = gpio;
            ADMUXB = adc_ref;
#elif defined(__AVR_ATmega2560__)
            ADMUX = adc_ref | (gpio & 0x07);
            ADCSRB &= ~(1<<MUX5);
            if( gpio > 8 )
                ADCSRB |= (1<<MUX5);
#else /* __AVR_ATtiny85__ || __AVR_ATtiny1634__ || __ATmega328P__ */
            ADMUX = adc_ref | gpio;
#endif

            ADCSRA = (1<<ADEN) | (1<<ADSC) | prescale;
            while( ADCSRA & (1<<ADSC) ) ;
            value = ADCW;
        }
    }
    return( value );
}