LCD 4 bit

I've just started with 8051 uC, this code's writed for LCD 4-bit , it worked but I can't understand why in the initial procedure (LCDinit() function), there's three sequential statements : "LCD control_init(0x30)"- or it's compulsory. Somebody help me. Thanks alot.


#include <string.h>
#include <at89x52.h>
#define LCD_PORT P2

// LCD 4 bit display
sbit BF = 0xA7;

sbit RS = P3^5;
sbit RW = P3^6;
sbit EN = P3^7;
void delay_5ms()
{
int i,j;
for(i=0;i<250;i++)
for(j=0;j<4;j++){}
}
void delay(long time){long i;for(i=1;i<time;i++){;}}
void delay_15ms()
{
int i,j;
for(i=0;i<250;i++)
for(j=0;j<100;j++){}
}

void LCDbusy(void)
{

BF = 1;
EN = 1;
RS = 0;
RW = 1;

while (BF==1) {EN=0;EN=1;}
RW = 0;
}

void LCDcontrol_init(unsigned char x)
{
LCD_PORT = x;
RS = 0;
RW = 0;
EN = 1;
delay(400);
EN = 0;
}

void LCDcontrol(unsigned char x)
{

LCD_PORT = (x & 0xF0);
RS = 0;
RW = 0;
EN = 1;
delay(400);
EN = 0;
delay(100);
x <<= 4;

LCD_PORT = (x & 0xF0);
EN = 1;
delay(400);
EN = 0;


//LCDbusy();
}

void LCDinit(void)
{

delay_15ms();
LCDcontrol_init(0x30);
delay_5ms();
LCDcontrol_init(0x30);
delay_5ms();
LCDcontrol_init(0x30);
delay_5ms();

LCDcontrol_init(0x20);
LCDbusy();
LCDcontrol(0x28);
LCDbusy();
LCDcontrol(0x0C);
LCDbusy();
LCDcontrol(0x06);
LCDbusy();
LCDcontrol(85);
LCDbusy();
LCDcontrol(0x01);
LCDbusy();
}

void LCDwrite(unsigned char c)
{
LCD_PORT = (c & 0xF0);
RS = 1;
RW = 0;
EN = 1;
delay(400);
EN = 0;
LCDbusy();
c <<= 4;
LCD_PORT = (c & 0xF0);
EN = 1;
delay(400);
EN = 0;
LCDbusy();

}
void LCDputs(unsigned char *s,unsigned char row)
{
unsigned char len;
if(row==1) LCDcontrol(0x80);
else LCDcontrol(0xC0);
len=strlen(s);
while(len!=0)
{
LCDwrite(*s);
s++;
len--;
}
}

void main()
{

LCDinit();
LCDputs("coming home",1);
while(1) {}
}

Ok i explain you the sequence
To initialize LCD there is a special init sequence. Which is usually not required when dealing with 8-bit mode, but is kind of necessary when working with 4-bit mode.

To initialize LCD, we first need to reset it.. so below is the reset sequence.

//First Init
LCDcontrol_init(0x30);
delay_5ms();
//second init
LCDcontrol_init(0x30);
delay_5ms();
//third init
LCDcontrol_init(0x30);
delay_5ms();

After this the LCD is reset properly, now we need to set the data-width of the LCD which is 4-bit so..

//set data width
LCDcontrol_init(0x20);

I hope you understood the above reset sequence..
after this reset sequence, busy flag is ready to read. and you LCD is ready work.