Embedded System Keypad Programming

by Online Tutorials Library July 14, 2022

Keypad Programming Using 8051 Microcontroller

Keypad is an analog switching device which is generally available in matrix structure. It is used in many embedded system application for allowing the user to perform a necessary task.

Consider the block diagram representation of interfacing keypad with microcontroller is:-

Keypad Programming1

A matrix keypad is consists of an arrangement of switches connected in matrix format in rows and columns. The rows and columns are connected with a microcontroller such that the rows of switches are connected to one pin and the columns of switches are connected to another pin of a microcontroller.

Consider the interfacing of Keypad with 8051 microcontroller using Proteus based Simulation is:-

Keypad Programming2

Consider the program to toggle the LED by pressing the switch is:-

  #include  sbit p=P3^0;  sbit q=P3^1;  sbit r=P3^2;  sbit s=P3^3;  void delay();  void main()  {  while(1)  {  p=0;  q=1;  r=1;  s=1;  delay();  p=1;  q=0;  r=1;  s=1;  void delay()  {  unsigned char i;  TMOD=0x20; //set timer mode//  for(i=0;i<2;i++) //double the time delay//  {  TL1=0x19; //set time delay//  TH1=0x00;  TR1=1; //timer on//  While(TF1==0); //check flag bit//  TF1=0;  }  TR1=0; //timer off//  }  

Consider the program to Switch ON the LED by pressing the key ‘1’ on the keypad is:-

   #include  sbit a1=P2^0;  sbit b1=P3^0;  sbit LED=P0^1;  void main()  {  a1=0;  if(b1==0)  {  LED=0xff;  }  }  

Consider the program to display a number 0, 1, 2,3,4,5 on a seven segment display by pressing the respective key on a keypad are:-

  #include  sbit  r1=P2^0;  sbit  c1=P3^0;  sbit  r2=P2^0;  sbit  c2=P3^0;  sbit a=P0^1;  void main()  {  r1=0; a=1;  if(c1==0)  {  a=0xFC;  }  if(c2==0)  {  a=0x60;  }  if(r1==0)  {  a=0xDA;  }  if(r2==0)  {  a=0xF2;  }  }  

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