44 lines
1.2 KiB
C
44 lines
1.2 KiB
C
#include "header.h"
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// 14.3.3 : alternate functions on port D
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// PD2 : - INT0 (External Interrupt 0 Input)
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// - PCINT18 (Pin Change Interrupt 18)
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// 12.4 : Interrupt Vectors in ATmega328 and ATmega328P
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// - INT0 : External Interrupt Request 0
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typedef enum {
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DOWN,
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UP
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} State;
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volatile uint8_t button_state = UP;
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// Table 13-2 : interrupt types
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#define INT0_LOW ((0 << ISC01) | (0 << ISC01))
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#define INT0_LOGICAL ((0 << ISC01) | (1 << ISC01))
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#define INT0_FALLING ((1 << ISC01) | (0 << ISC01))
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#define INT0_RAISING ((1 << ISC01) | (1 << ISC01))
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// use interruption to change led1 state when button1 is pressed
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int main() {
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MODE_OUTPUT(LED1);
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CLEAR_ELEM(LED1);
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MODE_INPUT(BUTTON1);
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PULLUP_ON(BUTTON1);
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SREG |= ENABLE_GLOBAL_INTERRUPT;
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EIMSK = (1 << INT0); // 13.2.2 : Enable INT0 interrupt (EIMSK – External Interrupt Mask Register)
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EICRA = INT0_LOGICAL; // Table 13-2 : trigger type (EICRA – External Interrupt Control Register A)
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while (1);
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}
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ISR(INT0_vect) {
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_delay_ms(50);
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button_state = (button_state == UP) ? DOWN : UP;
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if (button_state == UP) {
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TOGGLE_ELEM(LED1);
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}
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// EIFR = (1 << INTF0); // 13.2.3 : clear flag, why ? i think it only indicates that a trigger event has occured
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}
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