The mikroPascal PRO for AVR 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

Library Routines

• Keypad_Init
• Keypad_Key_Press
• Keypad_Key_Click

Keypad_Init

// Initialize PORTB for communication with keypad
var keypadPort : byte at PORTB;
var keypadPort_Direction : byte at DDRB;
...
Keypad_Init();

Keypad_Key_Press

var kp : byte;
...
kp := Keypad_Key_Press();

Keypad_Key_Click

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 : string[6];

// Keypad module connections
var keypadPort : byte at PORTC;
var keypadPort_Direction : byte at DDRC;
// End Keypad module connections

// LCD pinout definition
var LCD_RS : sbit at PORTD2_bit;
var LCD_EN : sbit at PORTD3_bit;
    LCD_D4 : sbit at PORTD4_bit;
    LCD_D5 : sbit at PORTD5_bit;
    LCD_D6 : sbit at PORTD6_bit;
    LCD_D7 : sbit at PORTD7_bit;

var LCD_RS_Direction : sbit at DDD2_bit;
    LCD_EN_Direction : sbit at DDD3_bit;
    LCD_D4_Direction : sbit at DDD4_bit;
    LCD_D5_Direction : sbit at DDD5_bit;
    LCD_D6_Direction : sbit at DDD6_bit;
    LCD_D7_Direction : sbit at DDD7_bit;
// end LCD pinout definitions

  begin
    oldstate := 0;
    cnt := 0;                               // Reset counter
    Keypad_Init();                          // Initialize Keypad
    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

            1: kp := 49;  // 1
            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

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