ADC0808

In this program 8051 is interfaced with adc adc0808

/*
MICROCONTROLLER -AT89S51/52
COMPILER ---MIKROC
BY---EMERGING TECHNOLOGIES --WWW.EMERGINGTECHS.ORG
*/
#define AN0 0
#define AN1 1
#define AN2 2
#define AN3 3
#define AN4 4
#define AN5 5
#define AN6 6
#define AN7 7
/*
MICROCONTROLLER -AT89S51/52
COMPILER ---MIKROC
BY---EMERGING TECHNOLOGIES --WWW.EMERGINGTECHS.ORG
*/
#define Data_Bus   P0
#define HalfCycleDelay 10
void InitADC(void);
unsigned char ReadADC(unsigned char);
    unsigned char ADC_Value = 0; // To capture ADC value
unsigned char Digit[3] = { 0,0,0 }; // To make digits to display on LCD
sbit LCD_RS at P1_1_bit;
sbit LCD_EN at P1_0_bit;
sbit LCD_D4 at P1_4_bit;
sbit LCD_D5 at P1_5_bit;
sbit LCD_D6 at P1_6_bit;
sbit LCD_D7 at P1_7_bit;
// End Lcd module connections
sbit switch1 at P3_0_bit;
sbit led1 at P3_1_bit;
sbit ADD_A at P2_0_bit;   // Address pins for selecting input channels.
sbit ADD_B at P2_1_bit;
sbit ADD_C at P2_2_bit;
sbit ale at P2_3_bit;     //address latch enable
sbit eoc at P2_4_bit;     //end of conversion
sbit oe at P2_5_bit;      //output enable
sbit start at P2_6_bit;   //start conversion
sbit clk at P2_7_bit;     // clock
//sfr input_port=0x80;//P0 port
void main(){
    Lcd_Init();                     // Initialize Lcd
    Lcd_Cmd(_LCD_CLEAR);            // Clear display
    Lcd_Cmd(_LCD_CURSOR_OFF);       // Cursor off
    Lcd_Out(1,6,"hai");             // Write text in first row
    delay_ms(1000);
    InitADC();
    delay_ms(1000);
    Lcd_Cmd(_LCD_CLEAR);
    while(1)
    {
        ADC_Value = ReadADC(AN1);
        Digit[2] = (unsigned char)( ADC_Value/100);   // Find out first digit
        Digit[1] = (unsigned char)( ADC_Value/10) - Digit[2]*10; // Find out second digit
        Digit[0] = ADC_Value - Digit[2]*100 - Digit[1]*10; // Find out third digit
        Lcd_Cmd(_LCD_CLEAR); // Clear LCD
        Lcd_Out(1,6,"temp= "); // Display string
        Lcd_Chr_cp(Digit[2]+0x30); // Display first digit
        Lcd_Chr_cp(Digit[1]+0x30); // Display second digit
        Lcd_Chr_cp(Digit[0]+0x30); // Display third digit
        if( switch1 ==0)   { led1=1; Lcd_Out(2,1,"gas found caution"); }
        else   { led1=0;   Lcd_Out(2,1,"                "); }
        delay_ms(100);
    }
}
unsigned char ReadADC(unsigned char Channel)
{
    unsigned int i = 0;
    unsigned int ADC_value = 0;
    // Select Channel
    switch(Channel)
    {
        case AN0: Add_C = 0;   Add_B = 0;   Add_A = 0; break;
        case AN1: Add_C = 0;   Add_B = 0;   Add_A = 1; break;
        case AN2: Add_C = 0;   Add_B = 1;   Add_A = 0; break;
        case AN3: Add_C = 0;   Add_B = 1;   Add_A = 1; break;
        case AN4: Add_C = 1;   Add_B = 0;   Add_A = 0; break;
        case AN5: Add_C = 1;   Add_B = 0;   Add_A = 1; break;
        case AN6: Add_C = 1;   Add_B = 1;   Add_A = 0; break;
        case AN7: Add_C = 1;   Add_B = 1;   Add_A = 1; break;
    }
    delay_us(HalfCycleDelay); // 250kHz Frequency
    ALE = 1; // Enable Address Latch
    CLK = 1; // Make CLK High
    delay_us(HalfCycleDelay); // 250kHz Frequency
    CLK = 0; // Make CLK Low
    START = 1; // Start ADC Conversion
    delay_us(HalfCycleDelay); // 250kHz Frequency
    CLK = 1; // Make CLK High
    ALE = 0; // Disable Address Latch
    delay_us(HalfCycleDelay); // 250kHz Frequency
    CLK = 0; // Make CLK Low
    START = 0; // Complete the start pulse
    for(i=0;i<2000;i++)
    {
        CLK = !CLK; // Toggle Clock
        delay_us(HalfCycleDelay); // 250kHz Frequency
        if(!EOC)   // Wait for EOC to be low
            break;
    }
    for(i=0;i<2000;i++)
    {
        CLK = !CLK; // Toggle Clock
        delay_us(HalfCycleDelay); // 250kHz Frequency
        if(EOC)   // Wait for EOC to be High
            break;
    }
    CLK = 0; // Make CLK Low
    OE = 1; // Enable Output
    delay_us(HalfCycleDelay); // 250kHz Frequency
    CLK = 1; // Make CLK High
    delay_us(HalfCycleDelay); // 250kHz Frequency
    CLK = 0; // Make CLK Low
    delay_us(HalfCycleDelay); // 250kHz Frequency
    CLK = 1; // Make CLK High
    ADC_value = Data_Bus; // Read value
    delay_us(HalfCycleDelay); // 250kHz Frequency
    OE = 0; // Disable Output
    CLK = 0; // Make CLK Low
    delay_us(HalfCycleDelay); // 250kHz Frequency
    return ADC_value; // Return ADC value
}
void InitADC(void)
{
    Add_A = 0;   // Make output
    Add_B = 0;   // Make output
    Add_C = 0;   // Make output
    ALE   = 0;   // Make output
    EOC   = 1;   // Make input
    OE    = 0;   // Make output
    START = 0;   // Make output
    CLK   = 0;   // Make output
    Data_Bus = 0xFF;   // Make Inputs
}