Hardware Interrupt and Seven-segment LED Digit Display Controlling Using an AVR Microcontroller http://youtu.be/XkO-7eyUWf8

gistfile1.cpp

#define F_CPU 16000000 //16MHz


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

typedef struct {
	volatile uint8_t *port;
	char pin;
} Segment;

volatile char led_num[] = {0, 0, 0};
	
void rand_num()
{
	int r = round(rand() / (RAND_MAX / 999));
	led_num[0] = floor(r/100);
	r = r - led_num[0]*100;
	led_num[1] = floor(r/10);
	r = r - led_num[1]*10;
	led_num[2] = r;
}

ISR(INT0_vect)
{
	cli();
	rand_num();
	sei();
}

int main(void)
{
	Segment segm[] {
		{&PORTC, PC5}, //A
		{&PORTD, PD1}, //B
		{&PORTC, PC4}, //C
		{&PORTC, PC2}, //D
		{&PORTC, PC0}, //E
		{&PORTD, PD0}, //F
		{&PORTC, PC1}, //G
		{&PORTC, PC3}, //DP
	};
	
	Segment digit[] {
		{&PORTD, PD6}, //1
		{&PORTB, PB0}, //2
		{&PORTD, PD7}, //3
	};

	
	
	//set output pins
	DDRC = (1<<DDC0) | (1<<DDC1) | (1<<DDC2) | (1<<DDC3) | (1<<DDC4) | (1<<DDC5);
	DDRB = (1<<DDB0);
	DDRD = (1<<DDD0) | (1<<DDD1) | (1<<DDD6) | (1<<DDD7);
	
	PORTD |= (1<<PD2); //PullUp
	GICR |= (1<<INT0); //Enable interruption
	MCUCR |= (1<<ISC01); //falling edge
	
	rand_num();
	
	sei();

	
    while(1)
    {
		int s = sizeof(segm)/sizeof(Segment);
		int s2 = sizeof(digit)/sizeof(Segment);
		
		for(int n=0; n < s2; n++)
		{
			for(int m=0; m < s2; m++)
			{
				*digit[m].port &= ~(1<<digit[m].pin);
			}
			
			char mask = 0;
			
			switch(led_num[n])
			{
				case 0: mask = 0b11111100; break;
				case 1: mask = 0b01100000; break;
				case 2: mask = 0b11011010; break;
				case 3: mask = 0b11110010; break;
				case 4: mask = 0b01100110; break;
				case 5: mask = 0b10110110; break;
				case 6: mask = 0b10111110; break;
				case 7: mask = 0b11100000; break;
				case 8: mask = 0b11111110; break;
				case 9: mask = 0b11110110; break;
				default:  mask = 0; break;
			}
			
			for(int i=0; i < s; i++)
			{
				char bit = mask & (1 << (s-i-1));
				
				if(bit)
				{
					*segm[i].port &= ~(1<<segm[i].pin);
				}
				else
				{
					*segm[i].port |= (1<<segm[i].pin);
				}
			}
			
			*digit[n].port |= (1<<digit[n].pin);
			
			_delay_ms(1);
		}		
		
    }

}