abs_sum.c

/*
    Copyright (C) 2019 SviMik

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <https://www.gnu.org/licenses/>.
*/

/*
Designed for Arduino Mini (ATmega328P)

Pin definitions:
Inputs: PC1, PC2
Output: PC3
LED1: PD7(-), PD6(+)
LED2: PD5(-), PD4(+)
No LED resistors are needed (built-in MCU pull-up resistors are used)
*/

#define F_CPU 16000000

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

#define LED1(on) if(on){PORTD|=(1<<6);}else{PORTD&=~(1<<6);}
#define LED2(on) if(on){PORTD|=(1<<4);}else{PORTD&=~(1<<4);}

uint8_t ticks_in = 0;
uint8_t pin_prev = 0;
ISR(PCINT1_vect){
	uint8_t pin_new = PINC;
	uint8_t changedbits = pin_new ^ pin_prev;
	pin_prev = pin_new;
	if(changedbits & (1 << 1)){
		ticks_in++;
	}
	if(changedbits & (1 << 2)){
		ticks_in++;
	}
}

int main(void){
	// Init
	PCICR|=(1<<PCIE1); // PCINT 1 enable
	PCMSK1|=(1<<PCINT9)|(1<<PCINT10); // PC1, PC2 - in
	DDRC |= (1<<3); // PC3 - out
	DDRD |= (1<<7); // PD5 - Virtual GND for LED1 (always 0)
	DDRD |= (1<<5); // PD5 - Virtual GND for LED2 (always 0)
	sei();
	// Main code
	uint8_t ticks_sent = 0;
	while(1){
		if(ticks_sent != ticks_in){
			PORTB ^= (1<<5); // Arduino led
			PORTC ^= (1<<3); // out
			_delay_us(250); // 250us is adequate for up to 2kHz output. Adjust if necessary
			ticks_sent++;
		}
		LED1(PINC & (1<<1));
		LED2(PINC & (1<<2));
	}
}