#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 32
#define OLED_RESET -1
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

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] = {13, 12, 27, 26}; //connect to the row pinouts of the keypad
byte colPins[COLS] = {25, 33, 32, 34}; //connect to the column pinouts of the keypad

void setup() {
  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println(F("SSD1306 allocation failed"));
    for(;;);
  }

  // display nilai awal (0)
  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(WHITE);
  display.setCursor(30, 7);
  display.print("Program Keypad");
  display.display();

  
  pinMode(rowPins[0], INPUT_PULLUP);
  pinMode(rowPins[1], INPUT_PULLUP);
  pinMode(rowPins[2], INPUT_PULLUP);
  pinMode(rowPins[3], INPUT_PULLUP);
  pinMode(colPins[0], OUTPUT);
  pinMode(colPins[1], OUTPUT);
  pinMode(colPins[2], OUTPUT);
  pinMode(colPins[3], OUTPUT);

}

void loop() {
  // scan each column of the keypad
  for (byte col = 0; col < COLS; col++) {
    digitalWrite(colPins[col], LOW);

    // check each row of the keypad
    for (byte row = 0; row < ROWS; row++) {
      if (digitalRead(rowPins[row]) == LOW) {
        // key pressed, print to OLED display
        display.clearDisplay();
        display.setCursor(0, 0);
        display.print("Key Pressed:");
        display.setCursor(0, 10);
        display.print(keys[row][col]);
        display.display();
        delay(500); // debounce
      }
    }

    digitalWrite(colPins[col], HIGH);
  }
}