digital multimeter using 8051

// Program to interface 3 LDRs with ADC 0808 using three input channels of ADC 0808. The output pins are connected to LCD to show intensity value between (0-255). Controller interrupt is used to generate the clock for driving the ADC 0808.
#include<reg51.h>
sbit ale=P1^0;  //address latch enable
sbit oe=P1^3;  //output enable
sbit sc=P1^1;  //start conversion
sbit eoc=P1^2;  //end of conversion
sbit clk=P1^7;  // clock
sbit ADD_A=P1^4;  //Address pins for selecting input channels.
sbit ADD_B=P1^5;
sbit ADD_C=P1^6;
sfr lcd_data_pin=0xA0;  //Port P2
sbit rs=P3^0;
sbit rw=P3^1;
sbit en=P3^6;
sfr input_port=0x80;  //Port P0
unsigned int key,value,number,ascii1,ascii2,ascii3,flag,temp1,key1/*,data1,data2,data3,data11,data12,data13,data21,data22,data23*/;

void timer0() interrupt 1  // Function to generate clock of frequency 500KHZ using Timer 0 interrupt.
{
clk=~clk;
}

void delay(unsigned int count)  // Function to provide time delay in msec.
{
int i,j;
for(i=0;i<count;i++)
  for(j=0;j<1275;j++);
}

void lcd_command(unsigned char comm)  //Function to send command to LCD.
{
lcd_data_pin=comm;
en=1;
rs=0;
rw=0;
delay(1);
en=0;
}
           
void lcd_data(unsigned char disp)  //Function to send data to LCD.
{
lcd_data_pin=disp;
en=1;
rs=1;
rw=0;
delay(1);
en=0;
}

lcd_dataa(unsigned char *disp)  //Function to send string data to LCD.
{
int x;
for(x=0;disp[x]!=0;x++)
{
  lcd_data(disp[x]);
}
}

void lcd_ini()  //Function to inisialize the LCD
{
lcd_command(0x38);  // for using 8-bit 2 row LCD
delay(5);
lcd_command(0x0F);  // for display on cursor blinking
delay(5);
lcd_command(0x80);
delay(5);  //Force cursor to blink at line 1 positon 0
}

void BCD()  // Binary to decimal conversion to send the data to LCD
{
  key1++;
  key=0;
  flag=0;
    number=input_port;
    value=number%10;
number=number/10;
ascii1=value+48;
if(number!=0)
{
  value=number%10;
  number=number/10;
  ascii2=value+48;
    flag=1;
}
else
{
  ascii2=48;
  flag=1;
}
if(number!=0)
{
  value=number%10;
    number=number/10;
    ascii3=value+48;
    key=2;
}
else
{
  ascii3=48;
  key=2;
}
if(key1==1)    
{
  lcd_command(0xC0);
}
if(key1==2)
{
  lcd_command(0xC5);
}
if(key1==3)
{
  lcd_command(0xCA);
}
if(key==2)
lcd_data(ascii3);
if(flag==1)
lcd_data(ascii2);
lcd_data(ascii1);
if(key1==3)
{
  key1=0;
  ascii3=0;
  ascii2=0;
  ascii1=0;
  delay(10);
} 
}
void adc()  //Function to drive ADC
{
while(1)
  {
   if(temp1==0)
   {
    ADD_C=0;  // Selecting input channel 1 using address lines
    ADD_B=0;
    ADD_A=0;
   }
   if(temp1==1)
   {
    ADD_C=0;  // Selecting input channel 2 using address lines
    ADD_B=0;
    ADD_A=1;
   }
   if(temp1==2)
   {
    ADD_C=0;  // Selecting input channel 3 using address lines
    ADD_B=1;
    ADD_A=0;
   }
   delay(2);
   ale=1;
   delay(2);
   sc=1;
   delay(1);
   ale=0;
   delay(1);
   sc=0;
   while(eoc==1);
   while(eoc==0);
   oe=1;
   BCD();
   delay(2);
   oe=0;
   temp1++;
   if(temp1==3)
   temp1=0;
  }
}

void main()
{
  eoc=1;
    ale=0;
   oe=0;
   sc=0;
  TMOD=0x02;  //Timer0 setting for generating clock of 500KHz using interrupt enable mode.
  TH0=0xFD;
  IE=0x82;
  TR0=1;
  temp1=0;
key1=0;
lcd_ini();
lcd_dataa("SN1:");
lcd_dataa(" SN2:");
lcd_dataa(" SN3:");
   adc();
}