Keypad Library
The mikroC 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 : |
extern sfr char keypadPort; | Keypad Port. | char keypadPort at PORTD; |
Library Routines
Keypad_Init
Prototype | void Keypad_Init(void); |
Returns | Nothing. |
Description | Initializes port for working with keypad. |
Requires | Global variable :
must be defined before using this function. |
Example | // Keypad module connections char keypadPort at PORTD; // End of keypad 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.
unsigned short kp, cnt, oldstate = 0;
char txt[6];
// Keypad module connections
char keypadPort at PORTD;
// End Keypad module connections
// LCD module connections
sbit LCD_RS at RB4_bit;
sbit LCD_EN at RB5_bit;
sbit LCD_D4 at RB0_bit;
sbit LCD_D5 at RB1_bit;
sbit LCD_D6 at RB2_bit;
sbit LCD_D7 at RB3_bit;
sbit LCD_RS_Direction at TRISB4_bit;
sbit LCD_EN_Direction at TRISB5_bit;
sbit LCD_D4_Direction at TRISB0_bit;
sbit LCD_D5_Direction at TRISB1_bit;
sbit LCD_D6_Direction at TRISB2_bit;
sbit LCD_D7_Direction at TRISB3_bit;
// End LCD module connections
void main() {
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, "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);
}
Courtsey : mikroc manual
Circuit Diagram
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| 4x4 Keypad PIC MikroC |
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