58 lines
1.2 KiB
C
58 lines
1.2 KiB
C
/*
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* Use the timers pwm to dim a light on demand.
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*/
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#define F_CPU 16000000UL
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#define __AVR_ATmega328P__
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#include <avr/interrupt.h>
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#include <avr/io.h>
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#include <util/delay.h>
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#define PWM_LOW 24
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#define PWM_HIGH 192
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int state = 0;
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// code for INT0
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ISR(INT0_vect) {
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OCR0A = PWM_HIGH; // max value for timer
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PORTB |= (1<<PORTB5);
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}
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// code for INT1
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ISR(INT1_vect) {
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OCR0A = PWM_LOW; // max value for timer
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PORTB &= ~(1<<PORTB5);
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}
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int main(void) {
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// read from D2 and D3, write to D6
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DDRD |= (1 << PORTD6);
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DDRB = 0xff; // used for internal led only
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PORTD |= (1 << PORTD2) | (1 << PORTD3); // pull up D2 and D3
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// enable external interruprs
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EIMSK |= (1 << INT0);
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EIMSK |= (1 << INT1);
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// trigger when anything changes
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EICRA |= (1 << ISC00); // for INT0
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EICRA |= (1 << ISC10); // for INT1
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// Timer 0
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// Mode: Fast PWM
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// Prescaler: /8
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// max: dynamic depending on pushed button
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TCCR0A |= (1 << WGM01) | (1 << WGM00); // Fast PWM Mode
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OCR0A = PWM_HIGH; // max value for timer
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TCCR0A |= (1 << COM0A1); // set non inverting mode, start initialized
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TCCR0B |= (1 << CS01); // enable with prescaler 8
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sei(); // magic interrupt macro
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while (1) {
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// do nothing
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}
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}
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