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54 lines
1.2 KiB
54 lines
1.2 KiB
9 years ago
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// Simple analog to digitial conversion
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#include <avr/io.h>
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#include <avr/pgmspace.h>
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#include <stdint.h>
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#include "analog.h"
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static uint8_t aref = (1<<REFS0); // default to AREF = Vcc
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void analogReference(uint8_t mode)
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{
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aref = mode & 0xC0;
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}
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// Arduino compatible pin input
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int16_t analogRead(uint8_t pin)
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{
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#if defined(__AVR_ATmega32U4__)
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static const uint8_t PROGMEM pin_to_mux[] = {
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0x00, 0x01, 0x04, 0x05, 0x06, 0x07,
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0x25, 0x24, 0x23, 0x22, 0x21, 0x20};
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if (pin >= 12) return 0;
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return adc_read(pgm_read_byte(pin_to_mux + pin));
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#elif defined(__AVR_AT90USB646__) || defined(__AVR_AT90USB1286__)
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if (pin >= 8) return 0;
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return adc_read(pin);
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#else
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return 0;
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#endif
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}
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// Mux input
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int16_t adc_read(uint8_t mux)
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{
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#if defined(__AVR_AT90USB162__)
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return 0;
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#else
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uint8_t low;
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ADCSRA = (1<<ADEN) | ADC_PRESCALER; // enable ADC
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ADCSRB = (1<<ADHSM) | (mux & 0x20); // high speed mode
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ADMUX = aref | (mux & 0x1F); // configure mux input
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ADCSRA = (1<<ADEN) | ADC_PRESCALER | (1<<ADSC); // start the conversion
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while (ADCSRA & (1<<ADSC)) ; // wait for result
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low = ADCL; // must read LSB first
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return (ADCH << 8) | low; // must read MSB only once!
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#endif
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}
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