#include <Keypad.h>

//Setting the number of rows and
//columns on a keypad.
//Arranging the numbers and letters in
//a matrix.
const int ROWS = 4;
const int COLS = 4;
char keysymb [ROWS] [COLS]= 
{
  {'1','2','3','A'},
  {'4','5','6','B'},
  {'7','8','9','C'},
  {'*','0','#','D'}
};

//Configurando los puertos por cada columna y linea
byte colPins[COLS] = { 5, 4, 3, 2};
byte rowPins[ROWS] = { 9, 8, 7, 6};

//Configurando el panel numérico
Keypad keypad = Keypad(makeKeymap(keysymb), rowPins, colPins, ROWS, COLS);

void setup() 
{
  portInit();
}

void loop() 
{
 PrintNum();

}

//Assigns a mode, INPUT or OUTPUT, to all of the ports that the keypad is connected.
//Initializes the Serial Monitor to print material onto the console.
void portInit()
{
  Serial.begin(115200);
  for (int i = 0; i < 4; i++)
  {
    pinMode(rowPins[i], INPUT);
  }

  for (int i= 0; i < 4; i++)
  {
    pinMode(colPins[i], INPUT);
  }
}

void PrintNum()
{
  char whichcharsym;

  //keypad.getKey() – waits for a user to input a value.
  //whichcharsym is a variable that will store a value.
  whichcharsym = keypad.getKey();
  if(whichcharsym != NO_KEY)
  {
    //The serial monitor will output a value every time the keypad has been pressed.
    Serial.print(whichcharsym);
  }
}