#include <LiquidCrystal_I2C.h>
#include <Keypad.h>

#define I2C_ADDR    0x27
#define LCD_COLUMNS 16
#define LCD_LINES   2

LiquidCrystal_I2C lcd(I2C_ADDR, LCD_COLUMNS, LCD_LINES);

const uint8_t ROWS = 4;
const uint8_t COLS = 4;
char keys[ROWS][COLS] = {
  {'0', '1', '2', '3'},
  {'4', '5', '6', '7'},
  {'8', '9', 'A', 'B'},
  {'C', 'D', 'E', 'F'}
};

uint8_t colPins[COLS] = {A3, A2, A1, A0};
uint8_t rowPins[ROWS] = { 5, 4, 3, 2 }; 

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

void setup() {
  lcd.begin(16, 2);
  lcd.backlight();
}

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

  if (key != NO_KEY) {
    lcd.clear();
    lcd.print(key);
  }
}