4x4 Keypad Issues

Thread Starter

steveG567

Joined Nov 4, 2008
1
I have written a program in C on a freescale 8 bit micro.

The code is:


Rich (BB code):
  while (column==1) 
  {
     
   PTBD = 0xFE;
  
    if (PTBD == 0xEE)
     {
      PTDD = 0x01; 
      lcd_delay(2000000);
      PTDD = 0x00; 
     }
     
     if (PTBD == 0xDE) 
     {
      PTDD = 0x02;
      lcd_delay(2000000);
      PTDD = 0x00;      
     }
     
     
     if (PTBD == 0xBE) 
     {
      PTDD = 0x03;
      lcd_delay(2000000);
      PTDD = 0x00; 
     }
     
     if (PTBD == (0x7E)) 
     {    
      PTDD = 0x04;
      lcd_delay(2000000);
      PTDD = 0x00; 
     }     
     else column = 2;
  }
 
 
  while (column==2) 
  {
     
    PTBD = 0xFD;
  
     
    if (PTBD == 0xED)
     {
      PTDD = 0x05; 
      lcd_delay(2000000);
      PTDD = 0x00; 
     }
     
     if (PTBD == 0xDD) 
     {
      PTDD = 0x06;
      lcd_delay(2000000);
      PTDD = 0x00;      
     }
     
     
     if (PTBD == 0xBD) 
     {
      PTDD = 0x07;
      lcd_delay(2000000);
      PTDD = 0x00; 
     }
     
     if (PTBD == (0x7D))
     { 
      PTDD = 0x08;
      lcd_delay(2000000);
      PTDD = 0x00; 
     }
     else column = 3;
  } 
       
   
   
   
  while (column==3) 
  {
     
    PTBD = 0xFB;
  
     
    if (PTBD == 0xEB)
     {
      PTDD = 0x09; 
      lcd_delay(2000000);
      PTDD = 0x00; 
     }
     
     if (PTBD == 0xDB) 
     {
      PTDD = 0x0A;
      lcd_delay(2000000);
      PTDD = 0x00;      
     }
     
     
     if (PTBD == 0xBB) 
     {
      PTDD = 0x0B;
      lcd_delay(2000000);
      PTDD = 0x00; 
     }
     
     if (PTBD == (0x7B))
     {
      
      PTDD = 0x0C;
        lcd_delay(2000000);
      PTDD = 0x00;       
     }
     else column = 4;
  }   
 
   
  while (column==4) 
  {
     
   PTBD = 0xF7;
  
     
    if (PTBD == 0xE7)
     {
      PTDD = 0x0D; 
      lcd_delay(2000000);
      PTDD = 0x00; 
     }
     
     if (PTBD == 0xD7) 
     {
      PTDD = 0x0E;
      lcd_delay(2000000);
      PTDD = 0x00;      
     }
     
     
     if (PTBD == 0xB7) 
     {
      PTDD = 0x0F;
      lcd_delay(2000000);
      PTDD = 0x00; 
     }
     
     if (PTBD == (0x77)) 
     { 
      PTDD = 0x10;
      lcd_delay(2000000);
      PTDD = 0x00; 
     }     
     else column = 1;
   }
Pins 4,5,6,7 are inputs pulled high
the rows are outputs pins 0,1,2,3 and polled.


Now, the 4th column works perfect. The first three dont. When I put an o-scope up to the pull up resistors, I get a voltage drop of around 0.5V, so the votlage is dropping, but not from 5-0V. I have NO IDEA why this is happening. ALl the code seems the same to me, why does column 4 work and not 1,2 or 3??

Any help would be great.
 
Last edited by a moderator:

hgmjr

Joined Jan 28, 2005
9,029
In addition to a schematic, you will need to post the rest of your source code.

The value of the variable "column" may be getting unintentionally altered somewhere else in your code.

hgmjr
 
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