Keypad Library

The mikroPascal PRO for PIC provides a library for working with 4x4 keypad. The library routines can also be used with 4x1, 4x2, or 4x3 keypad. For connections explanation see schematic at the bottom of this page.

External dependencies of Keypad Library

The following variable must be defined in all projects using Keypad Library:	Description :	Example :
`var keypadPort : byte; sfr; external;`	Keypad Port.	`var keypadPort : byte at PORTD;`

Keypad_Init

Prototype	procedure Keypad_Init();
Returns	Nothing.
Description	Initializes port for working with keypad.
Requires	Global variables : `keypadPort` - Keypad port must be defined before using this function.
Example	// Initialize PORTD for communication with keypad var keypadPort : byte at PORTD; ... Keypad_Init();

Keypad_Key_Press

Prototype	function Keypad_Key_Press(): byte;
Returns	The code of a pressed key (1..16). If no key is pressed, returns 0.
Description	Reads the key from keypad when key gets pressed.
Requires	Port needs to be initialized for working with the Keypad library, see Keypad_Init.
Example	var kp : byte; ... kp := Keypad_Key_Press();

Keypad_Key_Click

Prototype	function Keypad_Key_Click(): byte;
Returns	The code of a clicked key (1..16). If no key is clicked, returns 0.
Description	Call to `Keypad_Key_Click` is a blocking call: the function waits until some key is pressed and released. When released, the function returns 1 to 16, depending on the key. If more than one key is pressed simultaneously the function will wait until all pressed keys are released. After that the function will return the code of the first pressed key.
Requires	Port needs to be initialized for working with the Keypad library, see Keypad_Init.
Example	var kp : byte; ... kp := Keypad_Key_Click();

Library Example

This is a simple example of using the Keypad Library. It supports keypads with 1..4 rows and 1..4 columns. The code being returned by Keypad_Key_Click() function is in range from 1..16. In this example, the code returned is transformed into ASCII codes [0..9,A..F] and displayed on Lcd. In addition, a small single-byte counter displays in the second Lcd row number of key presses.

Copy Code To Clipboard

program Keypad_Test;
var kp, cnt, oldstate : byte;
    txt : array[6] of char;

// Keypad module connections
var keypadPort : byte at PORTD;
// End Keypad module connections

// Lcd module connections
var LCD_RS : sbit at RB4_bit;
    LCD_EN : sbit at RB5_bit;
    LCD_D4 : sbit at RB0_bit;
    LCD_D5 : sbit at RB1_bit;
    LCD_D6 : sbit at RB2_bit;
    LCD_D7 : sbit at RB3_bit;

var LCD_RS_Direction : sbit at TRISB4_bit;
    LCD_EN_Direction : sbit at TRISB5_bit;
    LCD_D4_Direction : sbit at TRISB0_bit;
    LCD_D5_Direction : sbit at TRISB1_bit;
    LCD_D6_Direction : sbit at TRISB2_bit;
    LCD_D7_Direction : sbit at TRISB3_bit;
// End Lcd module connections

  begin
    oldstate := 0;
    cnt := 0;                                // Reset counter
    Keypad_Init();                           // Initialize Keypad
    ANSEL  := 0;                             // Configure AN pins as digital I/O
    ANSELH := 0;
    Lcd_Init();                              // Initialize LCD
    Lcd_Cmd(_LCD_CLEAR);                     // Clear display
    Lcd_Cmd(_LCD_CURSOR_OFF);                // Cursor off
    Lcd_Out(1, 1, 'Key  :');                 // Write message text on LCD
    Lcd_Out(2, 1, 'Times:');

    while TRUE do
      begin
        kp := 0;                             // Reset key code variable

        // Wait for key to be pressed and released
        while ( kp = 0 ) do
          kp := Keypad_Key_Click();          // Store key code in kp variable
        // Prepare value for output, transform key to it's ASCII value
        case kp of
          //case 10: kp = 42;   // '*'       // Uncomment this block for keypad4x3
          //case 11: kp = 48;   // '0'
          //case 12: kp = 35;   // '#'
          //default: kp += 48;

            1: kp := 49;  // 1               // Uncomment this block for keypad4x4
            2: kp := 50;  // 2
            3: kp := 51;  // 3
            4: kp := 65;  // A
            5: kp := 52;  // 4
            6: kp := 53;  // 5
            7: kp := 54;  // 6
            8: kp := 66;  // B
            9: kp := 55;  // 7
           10: kp := 56;  // 8
           11: kp := 57;  // 9
           12: kp := 67;  // C
           13: kp := 42;  // *
           14: kp := 48;  // 0
           15: kp := 35;  // #
           16: kp := 68;  // D

        end;

        if (kp <> oldstate) then         // Pressed key differs from previous
          begin
            cnt := 1;
            oldstate := kp;
          end
        else                             // Pressed key is same as previous
          Inc(cnt);

        Lcd_Chr(1, 10, kp);              // Print key ASCII value on LCD

        if (cnt = 255) then              // If counter varialble overflow
          begin
            cnt := 0;
            Lcd_Out(2, 10, '     ');
          end;

        WordToStr(cnt, txt);             // Transform counter value to string


        Lcd_Out(2, 10, txt);             // Display counter value on LCD
    end;
  end.

HW Connection

4x4 Keypad connection scheme

Want more examples and libraries?
Find them on