Freenove Ultimate Starter Kit, Manual

Page: 242 / 286

Chapter 22 Matrix Keypad
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Keypad keypad = Keypad ( makeKeymap ( keys ), rowPins , colPins , ROWS , COLS ) ;
int main ( ){
printf ( "Program is starting ... \n" ) ;
i f ( wiringPiSetup () = = - 1 ) { //when initialize wiring failed, print message to screen
printf ( "setup wiringPi failed !" ) ;
r e turn 1 ;
}
char key = 0 ;
keypad . setDebounceTime ( 50 );
w h ile ( 1 ){
key = keypad . getKey (); //get the state of keys
i f ( key ) { //if a key is pressed, print out its key code
printf ( "You Pressed key : %c \n" , key );
}
}
r e turn 1 ;
}
In this project code, we use two custom library file " Keypad .hpp" and " Key .hpp". They are located in the same
directory with program files " MatrixKeypad .cpp", " Keypad .cpp" and " Key .cpp". Library Keypad is transplanted
from the Arduino library Keypad. And this library file provides a method to read the keyboard. By using this
library, we can easily read the matrix keyboard.
First, define the information of the matrix keyboard used in this project: the number of rows and columns,
code of each key and GPIO pin connected to each column and each row. It is necessary to include the header
file "
Keypad .hpp".
#include "Keypad.hpp"
#include <stdio.h>
const byte ROWS = 4 ; //four rows
const byte COLS = 4 ; //four columns
char keys [ ROWS ][ COLS ] = { //key code
{ '1' , '2' , '3' , 'A' },
{ '4' , '5' , '6' , 'B' },
{ '7' , '8' , '9' , 'C' },
{ '*' , '0' , '#' , 'D' }
} ;
byte rowPins [ ROWS ] = { 1 , 4 , 5 , 6 } ; //connect to the row pinouts of the keypad
byte colPins [ COLS ] = { 12 , 3 , 2 , 0 } ; //connect to the column pinouts of the keypad
And then, based on the above information, instantiate a Keypad class object to operate the matrix keyboard.
Keypad keypad = Keypad ( makeKeymap ( keys ), rowPins , colPins , ROWS , COLS ) ;
Set the debounce time to 50ms, and this value can be set based on the actual use of the keyboard flexibly,
with default time 10ms.
keypad . setDebounceTime ( 50 );