embedded c error for 8051 using 8255

Thread Starter

logu_

Joined Apr 3, 2013
3
I connected two 8255 ppi to 8051 to accessing keypad and lcd and other modules are connected in that.
I attached here my schematic diagram and embedded c programming for that.
while i simulating that i cant find out error.
Can anyone findout?

I connected lcd data port with port a of 8255 ppi1
I connected lcd control signal(wr,rd,cr) port with port b of 8255 ppi1(4000H)
I connected keypad(4*3) row pins with port c(pc0,pc1,pc2,pc3) of 8255 ppi1(8000H)
I connected keypad(4*3) column pins with port b(pb4,pb5,pb6) of 8255 ppi1

BElow is embedded c program for that,

Thanks in advance..:)

__________


Rich (BB code):
#include<reg51.h>
#define sec 100     
char xdata lcdctr _at_ 0x4001;
char xdata dataport _at_ 0x4000;
char xdata keyr _at_ 0x4002;
char xdata keyc _at_ 0x8001;
xdata cw[4003]=0x88;
xdata cw2[8003]=0x92;

void delay(unsigned int msec) //Time delay function
{
int i,j ;
for(i=0;i<msec;i++)
  for(j=0;j<1275;j++);
}

void lcd_cmd(unsigned char item)  //Function to send command to LCD
{
dataport = item;
lcdctr=0x04;
delay(1);
lcdctr=0x00;
return;
}

void lcd_data(unsigned char item) //Function to send data to LCD
{
dataport = item;
lcdctr=0x05;

delay(1);
lcdctr=0x01;
return;
}



void lcd_data_string(unsigned char *str) // Function to send string on LCD
{
int i=0;
while(str!='\0')
{
  lcd_data(str);
  i++;
  delay(10);
}
return;
}

void lcd(unsigned char str[16])  // Funtion to Initialize LCD
{
lcd_cmd(0x38);
lcd_cmd(0x0e);
//delay(sec);
lcd_cmd(0x01);
//delay(sec);
lcd_cmd(0x82);
//delay(sec);
lcd_data_string(str);
}  

void display(int a) //Display functon for LCD

{
switch(a)
{
  case 1:lcd("one 1");
    break;
  case 2:lcd("two 2");
    break;
  case 3:lcd("three 3");
    break;
  case 4:lcd("four 4");
    break;
  case 5:lcd("five 5");
    break;
  case 6:lcd("six 6");
    break;
  case 7:lcd("seven 7");
    break;
  case 8:lcd("EIGHT 8");
    break;
  case 9:lcd("NINE 9");
    break;
  case 0:lcd("ZERO 0");
    break;
  case 11:lcd("*");
    break;
  case 12:lcd("#");
    break;
    
}
}

void check_col1() //Function for checking column one
{
int temp;//row1=row2=row3=row4=1;
keyr=0xff;

keyr=0xfe;//row1=0;
   temp=0x10&keyc;
  if(temp==0x00)//if(col1==0)
{display(1);return;}

//row1=1;
keyr=0xfd;//row2=0;
 temp=0x10&keyc;//keyc*=0x10;
  if(temp==0x00)//if(col1==0)
display(4);
//row2=1;
keyr=0xfb;//row3=0;
 temp=0x10&keyc;//keyc*=0x10;
  if(temp==0x00)//if(col1==0)
display(7);
keyr=0xf7;
//row3=1;
//row4=0;
 temp=0x10&keyc;//keyc*=0x10;
  if(temp==0x00)//if(col1==0)
display(11); 
keyr=0xff;//row4=1;
}

void check_col2() //Function for checking column two
{
int temp;
keyr=0xff;

keyr=0xfe;//row1=0;
   temp=0x20&keyc;//keyc*=0x20;
  if(temp==0x00)//if(col1==0)
display(1);
//row1=1;
keyr=0xfd;//row2=0;
 temp=0x20&keyc;//keyc*=0x20;
  if(temp==0x00)//if(col1==0)
display(4);
//row2=1;
keyr=0xfb;//row3=0;
 temp=0x20&keyc;//keyc*=0x20;
  if(temp==0x00)//if(col1==0)
display(7);
keyr=0xf7;
//row3=1;
//row4=0;
 temp=0x20&keyc;//keyc*=0x20;
  if(temp==0x00)//if(col1==0)
display(11); 
keyr=0xff;
}

void check_col3() //Function for checking column three
{
int temp;
keyr=0xff;

keyr=0xfe;//row1=0;
   temp=0x40&keyc;//keyc*=0x40;
  if(temp==0x00)//if(col1==0)
display(1);
//row1=1;
keyr=0xfd;//row2=0;
 temp=0x40&keyc;//keyc*=0x40;
  if(temp==0x00)//if(col1==0)
display(4);
//row2=1;
keyr=0xfb;//row3=0;
 temp=0x40&keyc;//keyc*=0x40;
  if(temp==0x00)//if(col1==0)
display(7);
keyr=0xf7;
//row3=1;
//row4=0;
 temp=0x40&keyc;//keyc*=0x40;
  if(temp==0x00)//if(col1==0)
display(11); 
keyr=0xff;
}

void main()
{
//display(13);
//col1=col2=col3=1;  //Input Port
while(1)
{
int temp;
  keyr=0x00;//row1=row2=row3=row4=0;
  temp=0x10&keyc;//keyc*=0x10;
  if(temp==0x00)
  check_col1();
  else
  {
  temp=0x20&keyc;//keyc*=0x20;
   if(temp==0x00)
   check_col2();
   else
   {
   temp=0x40&keyc;//keyc*=0x40;
    if(temp==0x00)
    check_col3();
     }
   }
}

}
 
Last edited by a moderator:

Ian Rogers

Joined Dec 12, 2012
774
If you have connected A0 to the RS pin of the LCD then the Control is at 4000 and the data is on address 4001

RS = high data, low command
 

absf

Joined Dec 29, 2010
1,943
I connected two 8255 ppi to 8051 to accessing keypad and lcd and other modules are connected in that.
I attached here my schematic diagram and embedded c programming for that.
I dont see any schematic....or are you unable to attach it to your post?

Allen
 

absf

Joined Dec 29, 2010
1,943
I connected keypad(4*3) row pins with port c(pc0,pc1,pc2,pc3) of 8255 ppi1(8000H)
I connected keypad(4*3) column pins with port b(pb4,pb5,pb6) of 8255 ppi1
You can actually combine the 3x4 keyboard onto port c. The directions of upper & lower nibble can be set separately. There was an example on 8085 addressing the keypad using 8255 not long ago.

Allen
 
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