Matrix Keypad Not Working.

[gauravkothari23]

Hi Friends,
This is Gaurav Kothari and as i am very new to electonics want a bit help from you regarding matrix keypad.
I am trying to build electronic door lock system using 89S52 and 4x4 matrix keypad and 20x2 LCD display.
The keypad does work properly with proteus. but when i build a proper circuit and tried to make an entry using my keypad, it only shows me 3 numbers (7,8 and 9). whatever keys are pressed it displays me only 7,8 or 9.
my code for keypad is:

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int keypad() 
 {
   unsigned char dat[4][4]=
{
                            '7','8','9','%',
                            '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(0x06);
 
 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)
   return(dat[rowloc][0]);
   else if(colloc==0x0D)
   return(dat[rowloc][1]);
   else if(colloc==0x0B)
   return(dat[rowloc][2]);
   else
    return(dat[rowloc][3]);
    }
    }

---

can you please give me the solution for this problem.

- - - Updated - - -

My Circuit Diagram Is:

 

[KlausST]

Hi,

Well documented code...

You have to insert delay after output row and before input col.
Be sure to enable pullup at col.

Klaus

 

[gauravkothari23]

sorry friend.... as i am new to electronics and programming part......did not get you....
can u please explain me bit clearly or practically...

 

[gauravkothari23]

is it necessary to power the keypad(5V).
or have to add an 1K resistor at all ports

 

[KlausST]

Hi,

before you post your code next time, please document it, so we know what you want to do.
Reading - and understanding - undocumented code is hard to do.

****
insert delay:

/* output row */
    ROW=0xFE;
/* delay 1ms, wait for signals to settle */
      msdelay(1);
/* input col */
     colloc=COL;

you must do this every time you scan a row.

Klaus

 

[gauravkothari23]

can u plz explain me how to enable pullup at column.

 

[KlausST]

Hi,

I'm not familiar with this microcontroller,
So you have go read datasheet on your own.

Hint:
Column is on port2.
Open pdf and do a search on "pullup".
At least this is how i would do..

Klaus

 

[gauravkothari23]

Appreciate You and your ideas.

Have tried changing the code as u said...
it worked perfectly....
and u said about the pullup.
actually 89S52 has an internal pullup...
So i would really thank you a lot....
Thanks....

 

[KlausST]

Hi,

thanks. Good to hear that i could help.


Klaus