#include <Keypad.h>

#define ROW_NUM     4 // four rows
#define COLUMN_NUM  4 // four columns

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

byte pin_rows[ROW_NUM]      = {23, 22, 21, 19}; // GIOP23, GIOP22, GIOP21, GIOP19 connect to the row pins
byte pin_column[COLUMN_NUM] = {18, 5, 4, 2};   // GIOP18, GIOP5, GIOP4, GIOP2 connect to the column pins

Keypad keypad = Keypad( makeKeymap(keys), pin_rows, pin_column, ROW_NUM, COLUMN_NUM );

const int ledPin = 15;

void setup() {
  Serial.begin(9600);
  pinMode(ledPin, OUTPUT);
}

void loop() {
  char key = keypad.getKey();

  if (key == '1') { // check if button 1 is pressed
    digitalWrite(ledPin, HIGH);
  } 
  else if (key == '2'){
    digitalWrite(ledPin, LOW);
  }
}