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

// I2C LCD 20x4 at address 0x27
LiquidCrystal_I2C lcd(0x27, 20, 4);

// Keypad setup
const byte ROWS = 4;
const byte COLS = 4;

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

        byte rowPins[ROWS] = {12, 11, 10, 9};
        byte colPins[COLS] = {7, 6, 5, 4};

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

        void setup() {
          lcd.init();
            lcd.backlight();
              lcd.setCursor(0, 0);
                lcd.print("STM32 Keypad Input");
                }

                void loop() {
                  char key = keypad.getKey();
                    if (key) {
                        lcd.setCursor(0, 2);  // Row 2 of 20x4
                            lcd.print("Pressed: ");
                                lcd.print(key);
                                    lcd.print("     ");  // Clear trail
                                        delay(300);
                                          }
                                          }