#include <Keypad.h>

const uint8_t ROWS = 4;

const uint8_t COLS = 4;

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

uint8_t colPins[COLS] = { 16, 4, 2, 15 };


uint8_t rowPins[ROWS] = { 19, 18, 5, 17 };

Keypad keypad = Keypad(makeKeymap(keys), rowPins, colPins,ROWS,COLS);

void setup(){

  Serial.begin(9600);

}

void loop(){

  char key = keypad.getKey();
  if (key){
    Serial.print(key);
  }
}