Multiplexed 7 Segment With Timer0 Interrupt in ATmega16/32 for Stopwatch

AVR: Stopwatch With Interrupt Timer and Multiplexed 7 segment Display

Here we are connecting the 7 segment display with PORTA, i.e. Multiplexing of six-7segment display, with the control lines to PORTB. Following is the program to Interface the 7segments.

Crystal : 8MHz

Time: 0.125uSec

Prescaler: clk/1025

Timer Interrupt : 25mSec.

For 1sec , run this timmer for 40 times.

We can achieve max delay of appx. 35000uSec or 35mSec with 8MHz crystal frequency and prescaler (clk/1024).

Program: 

/*

 * two_7seg.c

 *

 * Created: 27-Oct-13 19:08:04

 *  Author: avrnarm

 */ 

/* PROGRAM to execute the counter with the multiplexed 7 segent display */

#define FUSE_CKSEL0 0

#define FUSE_CKSEL1 0

#define FUSE_CKSEL2 1

#define FUSE_CKSEL3 0

#include<avr/io.h>

#define F_CPU 8000000Ul

#include<util/delay.h>

#include<avr/interrupt.h>

unsigned int j,ss=0,mm=0,hh=0;

char ssd[]={0x3f,0x06,0x5b,0x4f,0x66,0x6d,0x7d,0x07,0x7f,0x6f}; // Hexadecimal values for the 7 Segment display generated by the look up table

char ssd_dec[]={0xbf,0x86,0xdb,0xcf,0xE6,0xEd,0xFd,0x87,0xff,0xEf}; // Hexadecimal values for the 7 Segment display generated by the look up table

int main(void)

{

DDRA=0xFF;

DDRB=0xFF;

//*********************TIMER***(8MHz crystal....clk/1024 prescaler......Obtained 25ms delay

TCNT0=61;

TCCR0=0x05;

TIMSK=(1<<TOIE0);

//*********************

sei();

while(1)

    {

// for seconds

PORTB=0xFF;

PORTA=ssd[(ss)/10];

PORTB=0b11111110;

_delay_ms(1);

PORTB=0xFF;

PORTA=ssd[(ss%10)];

               PORTB=0b11111101;

_delay_ms(1);

PORTB=0xFF;

// for minute

PORTB=0xFF;

PORTA=ssd[(mm)/10];

PORTB=0b11111011;

_delay_ms(1);

PORTB=0xFF;

PORTA=ssd_dec[(mm%10)];

PORTB=0b11110111;

_delay_ms(1);

PORTB=0xFF;

//for hour

PORTB=0xFF;

PORTA=ssd[(hh)/10];

PORTB=0b11101111;

_delay_ms(1);

PORTB=0xFF;

PORTA=ssd_dec[(hh%10)];

PORTB=0b11011111;

_delay_ms(1);

PORTB=0xFF;

if (ss==60)

{

ss=0;

mm++;

if (mm==60)

{

hh++;

mm=0;

ss=0;

}

}

    }

}

ISR(TIMER0_OVF_vect)

{

TCNT0=61;                                                          //Refill  the Timer

j++;

if(j==40)                                                                 //For delay of 1sec

{

ss++;

j=0;

}

}