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/*
* Copyright 2020 Daniel Friesel
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <avr/io.h>
#include "arch.h"
#include "driver/adc.h"
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uint16_t AVRADC::getPin_mV(uint8_t pin, uint16_t avcc)
{
if (avcc) {
// measure with AVCC reference
ADMUX = _BV(REFS0) | pin;
} else {
// measure with internal 1.1V bandgap refernce
ADMUX = _BV(REFS1) | _BV(REFS0) | pin;
}
// Enable ADC with /64 prescaler
ADCSRA = _BV(ADEN) | _BV(ADPS2);
// Wait for bandgap to stabilise (70us according to datasheet table 28-3)
arch.delay_ms(1);
// Start conversion
ADCSRA |= _BV(ADSC);
// wait until conversion is complete
while (ADCSRA & _BV(ADSC)) ;
uint8_t adcr_l = ADCL;
uint8_t adcr_h = ADCH;
uint16_t adcr = adcr_l + (adcr_h << 8);
// Disable ADC
ADCSRA &= ~_BV(ADEN);
if (avcc) {
return (uint32_t)avcc * adcr / 1023L;
} else {
return 1100L * adcr / 1023L;
}
}
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int16_t AVRADC::getTemp_mdegC(int16_t offset)
{
// Measure temperature probe with 1.1V bandgap reference
ADMUX = _BV(REFS1) | _BV(REFS0) | 0x08;
// Enable ADC with /64 prescaler
ADCSRA = _BV(ADEN) | _BV(ADPS2);
// Wait for bandgap to stabilise (70us according to datasheet table 28-3)
arch.delay_ms(1);
// Start conversion
ADCSRA |= _BV(ADSC);
// Wait for conversion to complete
while (ADCSRA & _BV(ADSC)) ;
// typical values: 242 mV @ -45 degC
// typical values: 314 mV @ +25 degC
// typical values: 380 mV @ +85 degC
// slope: 0.9090.. degC / mV at 25 .. 85 degC
// -> approx. 286.5 mV @ 0 degC / approx -260.45 degC @ 0 mV
// -> T[degC] = ADC[mV] * 0.91 - 261
// -> T[mdegC] = ADC[mV] * 91 - 26100
// slope: 0.9722.. mV / degC at -45 .. 25 degC
// slope: 0.942 mV / degC at -45 .. 85 degC
uint8_t adcr_l = ADCL;
uint8_t adcr_h = ADCH;
uint16_t adcr = adcr_l + (adcr_h << 8);
uint16_t vadc = 1100L * adcr / 1023L;
// adjust for chip-specific variations
vadc += offset;
int16_t temp_mdegc = vadc * 91 - 26100L;
// Disable ADC
ADCSRA &= ~_BV(ADEN);
return temp_mdegc;
}
uint16_t AVRADC::getVCC_mV()
{
// Measure internal 1.1V bandgap using VCC as reference
ADMUX = _BV(REFS0) | 0x0e;
// Enable ADC with /64 prescaler
ADCSRA = _BV(ADEN) | _BV(ADPS2);
// Wait for bandgap to stabilise (70us according to datasheet table 28-3)
arch.delay_ms(1);
// Start conversion
ADCSRA |= _BV(ADSC);
// Wait for conversion to complete
while (ADCSRA & _BV(ADSC)) ;
uint8_t adcr_l = ADCL;
uint8_t adcr_h = ADCH;
uint16_t adcr = adcr_l + (adcr_h << 8);
uint16_t vcc = 1100L * 1023 / adcr;
// Disable ADC
ADCSRA &= ~_BV(ADEN);
return vcc;
}
AVRADC adc;