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https://codeberg.org/scip/attinycore-makefile-tests.git
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53 lines
1.3 KiB
C
53 lines
1.3 KiB
C
/*
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Macros for easier usage of vcc measurements.
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For attiny8441 only.
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We use REFS=0 to select VCC as Reference. i.e. ADMUXB = 0 << REFS0
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We then use channel #13 to read the BandGap. i.e. ADMUXA = 13 << MUX0
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And calculate the value of VCC from the reading. i.e. ADCW / 1024 = 1.1 / VCC
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Rearrange i.e. VCC = 1.1 * 1024 / ADCW
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Thanks for the help of the guys at AVR-Freaks:
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https://www.avrfreaks.net/forum/measuring-vcc-attiny841-using-adc-and-internal-bandgap
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*/
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#include <util/delay.h>
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#ifndef VCC_8441_H
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#define VCC_8441_H
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// disable ADC globally
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#define adc_disable() ADCSRA &= ~(1<<ADEN);
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// enable
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#define adc_enable() ADCSRA = (1<<ADEN); _delay_ms(10);
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// use supply voltage VCC as reference
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// measure internal bandgap 1v1 voltage reference
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// via channel 13, see table 16-3
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// and do not left shift result
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#define adc_setup_vcc_measurement() \
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ADMUXB = (0<<REFS0); \
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ADMUXA = (13<<MUX0); \
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ADCSRB = (0<<ADLAR);
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// start measurement
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// and wait till complete
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#define adc_start() \
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ADCSRA |= _BV( ADSC ); \
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while( ( (ADCSRA & (1<<ADSC)) != 0 ) );
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/* return measured voltage, adc value between 1-1023
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Calculate like:
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>> 1.1 * 1024 / 225 #=> 5.006222222222223
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>> 1.1 * 1024 / 341 #=> 3.3032258064516133
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*/
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#define adc_get_adcw() ADCW;
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#define adc_get_vcc() 1.1 * 1024 / ADCW;
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#endif
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