#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(9600);

}

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