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Matrix Keypad Not Working.

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gauravkothari23

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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:
Code C - [expand]
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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:
 
Last edited by a moderator:

Hi,

Well documented code...

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

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

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

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:

Code: 
/* 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
 
can u plz explain me how to enable pullup at column.
 

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
 
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....
 

Hi,

thanks. Good to hear that i could help.


Klaus
 

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