Keypad Library

The mikroC 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

The following variable must be defined in all projects using Keypad Library:	Description :	Example :
`extern sfr char keypadPort;`	Keypad Port.	`char keypadPort at PORTB;`
`extern sfr char keypadPort_Direction;`	Direction of the Keypad Port.	`char keypadPort_Direction at DDRB;`

Keypad_Init

Prototype	void Keypad_Init(void);
Returns	Nothing.
Description	Initializes port for working with keypad.
Requires	Global variables : `keypadPort` - Keypad port `keypadPort_Direction` - Direction of the Keypad port must be defined before using this function.
Example	// Initialize PORTB for communication with keypad char keypadPort at PORTB; // Port direction char keypadPort_Direction at DDRB; // Lcd module connections sbit LCD_RS at PORTD2_bit; sbit LCD_EN at PORTD3_bit; sbit LCD_D4 at PORTD4_bit; sbit LCD_D5 at PORTD5_bit; sbit LCD_D6 at PORTD6_bit; sbit LCD_D7 at PORTD7_bit; sbit LCD_RS_Direction at DDD2_bit; sbit LCD_EN_Direction at DDD3_bit; sbit LCD_D4_Direction at DDD4_bit; sbit LCD_D5_Direction at DDD5_bit; sbit LCD_D6_Direction at DDD6_bit; sbit LCD_D7_Direction at DDD7_bit; // End Lcd module connections ... Keypad_Init();

Keypad_Key_Press

Prototype	char Keypad_Key_Press(void);
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	char kp; ... kp = Keypad_Key_Press();

Keypad_Key_Click

Prototype	char Keypad_Key_Click(void);
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	char kp; ... 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

unsigned short kp, cnt, oldstate = 0;
char txt[6];

// Keypad module connections
char  keypadPort at PORTB;
char  keypadPort_Direction at DDRB;
// End Keypad module connections

// LCD module connections
sbit LCD_RS at PORTD2_bit;
sbit LCD_EN at PORTD3_bit;
sbit LCD_D4 at PORTD4_bit;
sbit LCD_D5 at PORTD5_bit;
sbit LCD_D6 at PORTD6_bit;
sbit LCD_D7 at PORTD7_bit;

sbit LCD_RS_Direction at DDD2_bit;
sbit LCD_EN_Direction at DDD3_bit;
sbit LCD_D4_Direction at DDD4_bit;
sbit LCD_D5_Direction at DDD5_bit;
sbit LCD_D6_Direction at DDD6_bit;
sbit LCD_D7_Direction at DDD7_bit;
// End LCD module connections

void main() {
  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, "1");
  Lcd_Out(1, 1, "Key  :");                 // Write message text on LCD
  Lcd_Out(2, 1, "Times:");

  do {
    kp = 0;                                // Reset key code variable

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

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

    }

    if (kp != oldstate) {                  // Pressed key differs from previous
      cnt = 1;
      oldstate = kp;
    }
    else {                                 // Pressed key is same as previous
      cnt++;
    }

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

    if (cnt == 255) {                      // If counter varialble overflow
      cnt = 0;
      Lcd_Out(2, 10, "   ");
    }

    WordToStr(cnt, txt);                   // Transform counter value to string
    Lcd_Out(2, 10, txt);                   // Display counter value on LCD
  } while (1);
}

HW Connection

4x4 Keypad connection scheme

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