/*
  Filename:    Four button interrupt
  Author:      Reed
  Date:        2023/04/12
  Description: This program receives button inputs via interrupts and outputs which pin the interrupt arrived on.
*/

#include <avr/interrupt.h>
#include <avr/io.h>
#include <util/delay.h>
#include <avr/iomxx0_1.h>

volatile bool pinChanged = false;



void init_interrupt(void);


int main(){
  unsigned char val;
  Serial.begin(9600);

  DDRB = 0xF0;  //configure PORTB 0-3 as input
  PORTB = 0x0F; //configure pull-up resistors
  DDRA = 0xFF; //configure PORTA as output

  init_interrupt();

  while (true) {
    
   if(pinChanged){

     //if button 1(Red) is pressed, PINB = 1110.  We XOR with 1111 to obtain the value. 
     //eg. 1011 XOR 1111 = 0100.
     val = PINB ^ 0x0F;

     switch(val){

       case 1:
        Serial.println("Button 1: Red");
        _delay_ms(300);
        break;
      case 2:
        Serial.println("Button 2: Black");
        _delay_ms(300);
        break;
      case 4:
        Serial.println("Button 3: Green");
        _delay_ms(300);
        break;
      case 8:
        Serial.println("Button 4: Yellow");
        _delay_ms(300);
        break;
     }
    pinChanged = false;
    
    }
  }    

  return 0;
}

void init_interrupt(void){
  cli(); //clear global interrupt
  PCICR |= (1 << PCIE0);  //enable interrupt on PCINT 0-7.  Interrupts excecuted from PCI0 vector.
  PCMSK0 |= 0x0F;  //Enable interrupts on PCINT 0-3
  PCIFR |= (1 << PCIF0); //Clear interrupt flag 
  sei(); //set global interrupt
}

ISR(PCINT0_vect){
  pinChanged = true;
  PCIFR |= (1 << PCIF0); //Clear interrupt flag 
}