Four digit seven segment display interfacing using 8051 Micro-Controller

SOFTWARE: KEIL MICRO VISION 4.0

SIMULATOR: PROTEUS 8.0

CIRCUIT DIAGRAM:

CIRCUIT WORKING:

I have used four digit seven segment common anode display panel.Four digit display panel has 8 segment pins to send the data and 4 control pins to control the operation of the display ( 4 single 7 segment display units).Segment pins are connected to port 1 and control pins(1,2,3,4) are connected to port(2.0,2.1,2.2,2.3) pins respectively.

It is common anode (CA) display so in order to activate segment I have provided logic 0 to respective segment (as mentioned in the below table given in the program description).

The four digit display panel consists of four 7 segment(ca) display units.To activate required display unit(single 7 segment display unit ) of 4 digit display panel we need to send logic 1 to the respective control pin of the display unit (single 7 segment display unit) and to deactivate the display unit(single 7 segment display unit) we need to send logic 0.

PROGRAM:

#include<reg51.h>

#define digit P1

sbit sw1=P2^0;

sbit sw2=P2^1;

sbit sw3=P2^2;

sbit sw4=P2^3;

unsigned char ch[]={0xc0,0xf9,0xa4,0xb0,0x99,0x92,0x82,0xf8,0x80,0x90};

void display (unsigned long int);

void delay(unsigned int i);

void main()

{

int a=0;

while(1)

{

if(a>1000)

{

a=0;

}

display(a); //pass the value to display

a++;

}

}

void display (unsigned long int n) // display number

{

if(n==1000) // number =1000

{

digit=ch[(n/1000)]; //pass the value to port 1

sw1=1;

delay(1);

sw1=0;

digit=ch[((n%1000)/100)]; //pass the value to port 1

sw2=1;

delay(1);

sw2=0;

digit=ch[((((n%1000)%100)/10))]; //pass the value to port 1

sw3=1;

delay(1);

sw3=0;

digit=ch[n%10]; //pass the value to port 1

sw4=1;

delay(1);

sw4=0;

}

else if((n>=100)&&(n<1000)) //for numbers ranging from 100 to 999

{

P2=0X00;

digit=ch[((n%1000)/100)]; //pass the value to port 1

sw2=1;

delay(1);

sw2=0;

digit=ch[((((n%1000)%100)/10))]; //pass the value to port 1

sw3=1;

delay(1);

sw3=0;

digit=ch[n%10]; //pass the value to port 1

sw4=1;

delay(1);

sw4=0;

}

if((n>=10)&&(n<100)) // for numbers ranging from 10 to 99

{

P2=0X00;

digit=ch[((((n%1000)%100)/10))]; //pass the value to port 1

sw3=1;

delay(1);

sw3=0;

digit=ch[n%10]; //pass the value to port 1

sw4=1;

delay(1);

sw4=0;

}

else if(n<10) // for numbers less than 10

{

P2=0x00;

digit=ch[n%10]; //pass the value to port 1

sw4=1;

delay(1);

sw4=0;

}

}

void delay (unsigned int i) // delay generation

{

while(i>0)

{

TMOD=0X01; //timer0 mode 1

TL0=0Xf2; // delay of 1/16 of sec

TH0=0x1d;

TR0=1; // start the timer0

while(TF0==0); // wait for rollover

TR0=0; // stop the timer0

TF0=0; // clear overflow flag of timer0

i--;

}

}

PROGRAM DESCRIPTION:

First I have send the data which needs to be displayed to port 1 where segment pins of display panel are connected.After that I have activated required displays((single 7 segment display unit)) on the display panel using control pins.

I have used persistence of vision to display data on the 4 digit display(ca) panel.In order to achieve this I have activated the required display(single 7 segment display unit)by providing logic 1 to respective control pin and then after (1/16) seconds of delay I have provided logic 0 to that control pin.

For providing the delay I have used timer 0 of 8051 in mode 1(16 bit mode).I have written the program to display number up to 1000.

Calculation of timer value loaded in TH0 and TL0 register:

In micro-controller 8051 frequency is internally divided by 12.

I have taken the micro-controller with 11.0592 MHZ frequency.So the calculation is

• (11.0592 MHZ ) / 12 = 921600 HZ
• 1 / (921600) = 1.08*10^-6
• I want to generate delay of 1/16 seconds.
• Count= required time / controller time
• Count = (1/16) / (1.08*10^-6)
• Count = 57870.370=57870
• Value to be loaded in timer 0 register= 65536 - 57870 = 7666 = 1df2(hex)
• So in TH0=0X1d and TL0 = 0Xf2

I have send the data to port 1 according to the below table.

VIDEO: