source code:-
//----- reading the char or no from the keyboard----//
#include<reg51.h>
sfr ROW=0x80; //assigning PORT-0 to read rows
sfr COL=0xA0; //assigning PORT-2 to read colomns
sfr ldata=0x90; //assigning PORT-1 for LCD data
sbit rs=P3^0;
sbit rw=P3^1;
sbit en=P3^2;
sbit busy=P2^7;
void lcdcmd(unsigned char value);
void lcddata(unsigned char value);
void lcdready(void);
void msdelay(unsigned int itime);
void lcddisplay(unsigned char ch);
void clear(void);
void main()
{
unsigned char dat[4][4]={'7','8','9','%', // assigning key matrix
'4','5','6','*',
'1','2','3','-',
'C','0','=','+'};
unsigned char colloc,rowloc;
COL=0xFF;
ROW=0x00;
rs=0;
rw=0;
en=0;
busy=0;
/* setting LCD screen*/
ldata=0x00;
lcdcmd(0x38);
lcdcmd(0x0E);
lcdcmd(0x01);
lcdcmd(0x06);
lcdcmd(0x80);
while(1)
{
/* reading character from keyboard */
do
{
ROW=0x00;
colloc=COL;
colloc&=0x0F;
}while(colloc!=0x0F);
do
{
do
{
msdelay(25);
colloc=COL;
colloc&=0x0F;
}while(colloc==0x0F);
msdelay(25);
colloc=COL;
colloc&=0x0F;
}while(colloc==0x0F);
while(1)
{
ROW=0xFE;
colloc=COL;
colloc&=0x0F;
if(colloc!=0x0F)
{
rowloc=0;
break;
}
ROW=0xFD;
colloc=COL;
colloc&=0x0F;
if(colloc!=0x0F)
{
rowloc=1;
break;
}
ROW=0xFB;
colloc=COL;
colloc&=0x0F;
if(colloc!=0x0F)
{
rowloc=2;
break;
}
ROW=0xF7;
colloc=COL;
colloc&=0x0F;
if(colloc!=0x0F)
{
rowloc=3;
break;
}
}
if(colloc==0x0E)
lcddisplay(dat[rowloc][0]);
else if(colloc==0x0D)
lcddisplay(dat[rowloc][1]);
else if(colloc==0x0B)
lcddisplay(dat[rowloc][2]);
else
lcddisplay(dat[rowloc][3]);
}
}
/*displaying char on LCD screen*/
void lcddisplay(unsigned char x)
{
if(x=='C')
{
clear();
}
else
lcddata(x);
}
/* sending commands to LCD display to act in command mode */
void lcdcmd(unsigned char value)
{
lcdready();
ldata=value;
rs=0;
rw=0;
en=1;
msdelay(1);
en=0;
}
/* sending commnad to LCD to display characters*/
void lcddata(unsigned char value)
{
lcdready();
ldata=value;
rs=1;
rw=0;
en=1;
msdelay(20);
en=0;
}
/* checking LCD buffer for free */
void lcdready(void)
{
busy=1;
rs=0;
rw=1;
if(busy==1)
{
en=0;
msdelay(20);
en=1;
}
}
/* generating delay*/
void msdelay(unsigned int value)
{
unsigned int i,j;
for(i=0;i<value;i++)
for(j=0;j<100;j++);
}
void clear(void)
{
lcdcmd(0x01);
}
