#include <Keypad.h>

const byte FILAS = 4;
const byte COLUMNAS = 4;

byte filasPines[FILAS] = {13, 12, 14, 27};
byte columnasPines[COLUMNAS] = {26, 25, 33, 32};

char teclas[FILAS][COLUMNAS] = {
  {'1', '2', '3', 'A'},
  {'4', '5', '6', 'B'},
  {'7', '8', '9', 'C'},
  {'*', '0', '#', 'D'}
};

Keypad teclado = Keypad(makeKeymap(teclas), filasPines, columnasPines, FILAS, COLUMNAS);
char caracter;

void setup() {
  Serial.begin(9600);
}

void loop() {
  caracter = teclado.getKey();
  if (caracter) {
    Serial.println(caracter);
  }
}