Aim:
The main aim of this project is how to interface 7-segment and display 0 to 99 values on 7-segments.
Description:
Introduction
Till now you have learn what is an embedded system, basic memory
architecture of a microcontroller, how to implement assembly language
and use of some softwares like pinnacle 52, keil-C and flash magic; we
also have come across how to interface LEDs from a microcontroller and
how to generate different pattern through it. now its time to move
forward and learn one more step ahead towards the completion of our
6-weak training. so here today we will learn about 7-Segment display;
How to interface and program it; and some of the applications of it.
7-Segment Display
A 7-Segment display is a useful electronic component use to
produce numeric, alphabetic and some non-alphabetic symbols using a
specific arrangement of LEDs as shown in figure here.
A 7-Segment display has 10-Pins representing each a, b, c, b, e, f, gand h LEDs respectively along with two extra pins for GND andVSS. following shown an original 7-Segment display device along with its pin diagram. LED h is also denoted by symbol dp.
As we have studied in LED interfacing a 7-segment display is also
interfaced in same way as it is also made of LEDs. So we can interface
LEDs in three ways bu here difference is that 7-Segment displays comes
in two types by manufacturers i.e. “Common Anode” and “Common Cathode“; the logics are shown in figure below.
and thus which logic is o implement is on the bases of these specifications provided by manufacturer.
Digit Drive Pattern:
To display the digits on 7 segment, we need to glow different logic
combinations of segments. For example if you want to display the digit 3
on seven segment then you need to glow the segments a, b, c, d and g.
The below table show you the Hex decimal values what we need to send
from PORTB to Display the digits from 0 to 9.
| DIGIT | DP | G | F | E | D | C | B | A | HEX VALUE |
| 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 0x3f |
| 1 | 0 | 0 | 0 | 0 | 0 | 1 | 1 | 0 | 0x06 |
| 2 | 0 | 1 | 0 | 1 | 1 | 0 | 1 | 1 | 0x5b |
| 3 | 0 | 1 | 0 | 0 | 1 | 1 | 1 | 1 | 0x4f |
| 4 | 0 | 1 | 1 | 0 | 0 | 1 | 1 | 0 | 0x66 |
| 5 | 0 | 1 | 1 | 0 | 1 | 1 | 0 | 1 | 0x6d |
| 6 | 0 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 0x7d |
| 7 | 0 | 0 | 0 | 0 | 0 | 1 | 1 | 1 | 0x07 |
| 8 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 0x7f |
| 9 | 0 | 1 | 1 | 0 | 0 | 1 | 1 | 1 | 0x67 |
Block Diagram
Schematic
Code
// ******************************************************
// Project: 0 to 99 display in 7-segments using atmega8
// Author: Hack Projects India
// Module description: Operate two 7-segments
// ******************************************************
#define F_CPU 8000000UL
#include <avr/io.h>
#include<util/delay.h>
int main(void)
{
DDRB=0xff;
DDRD=0xff;
int i,j,k,l,a[10]={0x3f,0x06,0x5b,0x4f,0x66,0x6d,0x7c,0x07,0x7f,0x67};
while(1)
{
for(k=0;k<10;k++)
{
for(l=0;l<10;l++)
{
PORTD=~0x02;
PORTB=a[k];
_delay_ms(100);
PORTD=~0x01;
PORTB=a[l];
_delay_ms(1000);
}
}
}
}
Downloads:
The code was compiled in Atmel Studio 6 and simulation was made in Proteus v7.7.
To download code and proteus simulation click here.
Further Reading suggestions:
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