Setting up Interrupts on atmega328 in pure C

I am currently working on an Arduino Uno Board and I am trying to write it in pure C without the use of Arduino's Libraries.

My project which I am working should work like this:

Set LEDs PB0 to BP7 ON and OFF.
Set interrupt on PD2 connected to a Button.
When the Button is pressed the LEDs should STOP (pause).
When the Button is pressed Again the LEDs should turn ON again
starting from the last LED which was OFF.

To be more precise:

The function play() is called
LEDs are starting to blink one after other
If I press the BUTTON the play() function should STOP

This means that if the LED connected to PB3 was last LED ON, when I press the Button again the function play() should continue from PB4.

Here is what I have so far:

#ifndef F_CPU
#define F_CPU 16000000UL
#endif

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

void play( void );

volatile uint8_t buttonWasPressed = 0;
const unsigned char LEDS[] = { PB0, PB1, PB2, PB3, PB4, PB5 };

int main(void)
{
    DDRB = 0xFF;  /// Set PORTB as OUTPUT

    DDRD  |=  ( 1 << PD7 );     /// Set PIN7 IN DDRD as INPUT
    PORTD &= ~( 1 << PD7 );     /// Set PIN7 on PORTD to LOW
    DDRD  &= ~( 1 << PD2 );     // Clear the PD2 pin and set PD2 (PCINT0 pin) now as input
    PORTD |= (1 << PD2);        // Set PIN PD2 as INPUT with pull-up enabled

    EICRA |= (1 << ISC00);      // set INT0 to trigger on ANY logic change
    EIMSK |= (1 << INT0);       // Turns on INT0
    sei();                      // turn on interrupts

    while(1)
    {
        play();
    }
}

ISR (INT0_vect)
{

    uint8_t buttonState = PIND & ( 1 << PD2 );
    if ( buttonState )
    {
        if ( buttonWasPressed == 0 )
        {
            PORTD ^= ( 1 << PD7 );  /// SET PIN 4 IN PORT B TO LOW
            _delay_ms( 200 );
            buttonWasPressed = 1;   /// update button state
        }
    }
    else                            /// The button is not pressed
    {
        buttonWasPressed = 0;       /// Update the button state
    }
}

void play( void )
{
    for ( uint8_t i = 0 ; i < 6 ; i++ )
    {
        PORTB |= ( 1 << LEDS[i] );  ///Turn LED ON
        _delay_ms( 250 );
        PORTB &= ~( 1 << LEDS[i] ); ///Turn LED OFF
        _delay_ms( 250 );
    }
}

At this point the function play() runs forever and if I press the Button the LED connected to PD7 goes ON and OFF.

Solution

Try something like this.

#ifndef F_CPU
#define F_CPU 16000000UL
#endif

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

void play( unsigned int a );
ISR (INT0_vect);

volatile uint8_t buttonWasPressed = 0;
const unsigned char LEDS[] = { PB0, PB1, PB2, PB3, PB4, PB5 };
unsigned int ledNum = 0;

int main(void)
{
    DDRB = 0xFF;  /// Set PORTD as OUTPUT

    DDRD  |=  ( 1 << PD7 );     /// Set PIN7 IN DDRD as INPUT
    PORTD &= ~( 1 << PD7 );     /// Set PIN7 on PORTD to LOW
    DDRD  &= ~( 1 << PD2 );     // Clear the PD2 pin and set PD2 (PCINT0 pin) now as input
    PORTD |= (1 << PD2);        // Set PIN PD2 as INPUT with pull-up enabled

    EICRA |= (1 << ISC00);      // set INT0 to trigger on ANY logic change
    EIMSK |= (1 << INT0);       // Turns on INT0
    sei();                      // turn on interrupts

    while(1)
    {
        if(buttonWasPressed == 1)
            play(ledNum);

    }
}

ISR (INT0_vect)
{

    uint8_t buttonState = PIND & ( 1 << PD2 );
    if ( buttonState )
    {
        if ( buttonWasPressed == 0 )
        {
            PORTD ^= ( 1 << PD7 );  /// SET PIN 4 IN PORT B TO LOW
            _delay_ms( 200 );
            buttonWasPressed = 1;   /// update button state
        }
    }
    else                            /// The button is not pressed
    {
        buttonWasPressed = 0;       /// Update the button state
    }
}

void play( unsigned int a )
{
    for ( uint8_t i = a ; i < 6 ; i++ )
    {
        PORTB |= ( 1 << LEDS[i] );  ///Turn LED ON
        _delay_ms( 250 );
        PORTB &= ~( 1 << LEDS[i] ); ///Turn LED OFF
        _delay_ms( 250 );
        ledNum=i;
    }
}

by defining a variable to save which LED it was on then whenever it is resumed it will start from the last lit LED. check it out. Change if there is anything. I just gave the idea. hope it helps :)