#include<Keypad.h>

const byte ROWS = 4; 
const byte COLS = 4;
char hexaKeys[ROWS][COLS] = {
  {'1','2','3','A'},
  {'4','5','6','B'},
  {'7','8','9','C'},
  {'*','0','#','D'}
};
byte rowPins[ROWS] = {10, 11, 12, 13}; 
byte colPins[COLS] = {6, 7, 8, 9};

/* initialize an instance of class NewKeypad */
Keypad customKeypad = Keypad( makeKeymap(hexaKeys),  rowPins, colPins, ROWS, COLS); 

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

void loop(){
  char customKey = customKeypad.getKey();

  if (customKey){
Serial.println(customKey);
  }
}