#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] = {5, 4, 3, 2};
uint8_t rowpins[rows] = {9, 8, 7, 6};

Keypad keypad = Keypad(makeKeymap(keys), rowpins, colpins, rows, cols);

void setup() 
{
  Serial.begin(115200);
}

void loop() 
{
  char key = keypad.getKey();
  if (key != NO_KEY)
  Serial.println(key);
}