8. Consider a push button switch SwO connected to pin INT0 external interrupts o

Question

8. Consider a push button switch SwO connected to pin INT0 external interrupts of an ATMega8 AVR. 8 LEDS are connected to port PB0 PB7 on the same AVR. These LEDS are connected such a lit LED displays that the output port is on logic level 1. On start-up, TASKl is executed and continue indefinitely. If the push-button switch SW0 is pressed, TASKI is paused and TASK2 is carried out after which TASKl is resumed. TASK1- A roll action is performed using the LEDs: The first LED is lit and roll down to the last LED then back to the first LED. This operation is done indefinitely. TASK2- ALL the LEDs blink five (5) times » Write a complete C program that implements the desired tasks

Explanation / Answer

Answer :- The code is written below-

#include <avr/io.h>

#include <avr/interrupt.h>

#define F_CPU 4000000UL

#include <util/delay.h>

#define DataPort PORTB // Using PortB as our Dataport

#define DataDDR DDRB

//Interrupt Service Routine for INT0

ISR(INT0_vect)

{

unsigned char i, temp;

_delay_ms(500); // Software debouncing control

temp = DataPort; // Save current value on DataPort

/* This for loop blink LEDs on Dataport 5 times*/

for(i = 0; i<5; i++)

{

DataPort = 0x00;

_delay_ms(500); // Wait 0.5 seconds

DataPort = 0xFF;

_delay_ms(500); // Wait 0.5 seconds

}

DataPort = temp; //Restore old value to DataPort

}

int main(void)

{

DDRD = 1<<PD2; // Set PD2 as input (Using for interupt INT0)

PORTD = 1<<PD2; // Enable PD2 pull-up resistor

DataDDR = 0xFF; // Configure Dataport as output

DataPort = 0x01; // Initialise Dataport to 1

GICR = 1<<INT0; // Enable INT0

MCUCR = 1<<ISC01 | 1<<ISC00; // Trigger INT0 on rising edge

sei(); //Enable Global Interrupt

while(1)

{

if(DataPort >= 0x80)

DataPort = 1;

else

DataPort = DataPort << 1; // Shift to the left

_delay_ms(500); // Wait 5 seconds

}

}

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