led2_button_interaction.c

/*
 * main.c
 *
 * Created: 4/17/2024 5:52:27 PM
 *  Author: USER
 */ 

#include <avr/io.h>
#include <util/delay.h>
#include <xc.h>

int direction = 0;
int next_count = 0;
int masks[] = { 0b00001000, 0b000000100, 0b00000010, 0b00000001 };

int main(void)
{
	DDRD = 0x0f;
	PORTD = 0xff;
    while(1)
    {
		// wait 10ms each, total 100ms to detect the button
		for (int i = 0; i < 10; i++) {
			delay(10);
			check_button();
		}
		
		// if iterations are done, reset.
		if (next_count > 3) {
			next_count = 0;
		}
		if (next_count < 0) {
			next_count = 3;
		}
		
		PORTD = PORTD & 0xf0 // <--- don't change input register.
				 | masks[next_count]; // <--- mask based on interation.
		
		if (direction) next_count++; else next_count--;
	}
}

void check_button() {
	if (~PIND & 0b00010000) { // if button 1 has pressed
		direction = 0;
	}
	
	if (~PIND & 0b00100000) { // if button 2 has pressed
		direction = 1;
	}
}

void delay(int ms) {
	for (int i = 0; i < ms; i++) _delay_ms(1);
}