Setting up Interrupts on atmega328 in pure C

Question

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.

Answer 1

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 :)

Answer 2

I managed to fix it with the help of @Althaf1467.

The working code is:

#ifndef F_CPU
#define F_CPU 16000000UL
#endif

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

#define LEDS_LENGTH 6

void play( void );

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

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

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

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

    while(1)
    {
        play();
    }
}

ISR ( INT0_vect )
{
    if ( PIND & ( 1UL << PD2 ) )
    {
        PORTD ^= ( 1UL << PD7 );    /// SET PIN 4 IN PORT B TO LOW
        state ^= ( 1 << 0 );        /// Swap the Buton State from 0 to 1 and back to 0 ...
        _delay_ms( 500 );
    }
}

void play( void )
{
    static uint8_t step = 0;
    while( step < LEDS_LENGTH )
    {
        if ( state == 1 )
        {
            break;
        }
        PORTB |=  ( 1UL << LEDS[ step ] );  /// Turn LED ON
        _delay_ms( 250 );

        PORTB &= ~( 1UL << LEDS[ step ] );  /// Turn LED OFF
        _delay_ms( 250 );

        step++;
    }

    if ( step == LEDS_LENGTH )
    {
        step = 0;
    }
}