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/************************************************************************/
/* */
/* 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 );
}
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