/* 
  Filename: intEx1 
  Author:  
  Date:  
  Description:  
Code to test external interrupts: every time PCINT0 is triggered, 
 the red shield LED7 is toggled  
*/ 
 
#include <avr/io.h> 
#include <avr/interrupt.h> 
#include <avr/pgmspace.h> 
#include <util/delay.h> 
//user-defined function for the initialisation of the external interrupt PCINT0 

volatile unsigned char Pin0Change = 0;  //global variable, initialised to False 
volatile unsigned char buttons = 0b00000000;   // Global variable for debugging code 

int main(void) 
{//--- User initializations. 
    Serial.begin(115200);
    DDRB = 0b11111100;                       // NOTE: configure only PB0 (PCINT0) as input and 
    PORTB = 0b00000011;                      // activate only its pull up resistor, and turn off LED 
    DDRA = 0xFF;                       // All Port A configured as output 
    //SREG = SREG | 0x80;
 
    pcint0_init();                     // initialise registers to enable PCINT0 
 
    while(1) 
    { 
        if(Pin0Change)                  // Check if pin change detected 
        { 
         
          //buttons=0b11110000| buttons;
           Serial.println(buttons);
          switch(buttons)
          {
            case 0x01:
            Serial.println("button 1");
           // Pin0Change=0;
            blink_led();
            break;

            case 0x02:
            Serial.println("button 2");
            blink_led();
            break;

            case 0x04:
            Serial.println("button 3");
            blink_led();
            break;

            case 0x08:
            Serial.println("button 4");
            blink_led();
            break;
          }
          Pin0Change=0;
        } 
    } 
}
//user-defined function for the initialisation of the external interrupt PCINT0 
void pcint0_init(void)        //enable pcint0 (all port b) as an interrupt
{ 
    cli();                             // SREG = 0 stop seeing others INTERRUPTS
    PCICR = PCICR | (1 << PCIE0);     //PCICR PIN CHANGE INTERUPT CONTROL REGISTER, LIKE CHECKING ALL THE PINS ON PORT B
    PCMSK0 = PCMSK0 | (1<<PCINT0)|(1<<PCINT1)| (1<<PCINT2) | (1<<PCINT3);  //define which pins to check in port B
    PCIFR |= (1 << PCIF0); 
    sei();                             // SREG = 1 starts seeing all interrupts again
} 

//interrupt-service routine 
ISR(PCINT0_vect) 
{ 
    Pin0Change = 1; 
    buttons = PINB;
    PCIFR = PCIFR | (1 << PCIF0);      // re-arm the interrupt – IMPORTANT!!! 
} 
void blink_led(void)
{
  PORTA |= 0x80; 
  _delay_ms(1000); 
  PORTA &= ~0x80; 
  Pin0Change = 0;
}