#include <LiquidCrystal_I2C.h>  // Supported in Tinkercad for I2C LCD
#include <Wire.h>               // For I2C communication

// Keypad setup (manual scanning for 4x4)
const int rowPins[4] = {5, 4, 3, 2};    // Rows
const int colPins[4] = {9, 8, 7, 6};    // Columns
char keyMap[4][4] = {                   // Key layout
  {'1', '2', '3', 'A'},
    {'4', '5', '6', 'B'},
      {'7', '8', '9', 'C'},
        {'*', '0', '#', 'D'}
        };

        // LCD setup (I2C at address 0x27; change to 0x3F if needed)
        LiquidCrystal_I2C lcd(0x27, 16, 2);  // Address, columns, rows

        void setup() {
          Serial.begin(9600);  // For console output
            
              // Set up keypad pins
                for (int i = 0; i < 4; i++) {
                    pinMode(rowPins[i], OUTPUT);
                        digitalWrite(rowPins[i], HIGH);  // Rows high by default
                            pinMode(colPins[i], INPUT_PULLUP);  // Columns as inputs with pull-ups
                              }
                                
                                  lcd.init();          // Initialize LCD
                                    lcd.backlight();     // Turn on backlight
                                      lcd.clear();
                                        lcd.print("Keypad ready");  // Initial message
                                          Serial.println("Keypad ready. Press a key...");
                                          }

                                          void loop() {
                                            char key = getKey();  // Get pressed key
                                              
                                                if (key != '\0') {    // If a key was pressed
                                                    Serial.print("Key pressed: ");
                                                        Serial.println(key);
                                                            
                                                                // Display on LCD
                                                                    lcd.clear();
                                                                        lcd.setCursor(0, 0);
                                                                            lcd.print("Key pressed: ");
                                                                                lcd.print(key);
                                                                                    delay(300);  // Basic debounce
                                                                                      }
                                                                                      }

                                                                                      // Manual function to scan keypad
                                                                                      char getKey() {
                                                                                        for (int r = 0; r < 4; r++) {
                                                                                            digitalWrite(rowPins[r], LOW);  // Set current row low
                                                                                                for (int c = 0; c < 4; c++) {
                                                                                                      if (digitalRead(colPins[c]) == LOW) {  // Key pressed
                                                                                                              while (digitalRead(colPins[c]) == LOW);  // Wait for release
                                                                                                                      digitalWrite(rowPins[r], HIGH);  // Reset row
                                                                                                                              return keyMap[r][c];
                                                                                                                                    }
                                                                                                                                        }
                                                                                                                                            digitalWrite(rowPins[r], HIGH);  // Reset row
                                                                                                                                              }
                                                                                                                                                return '\0';  // No key
                                                                                                                                                }