#define PL_PIN   27  // Parallel Load (pin 1 on 74HC165)
#define CP_PIN   18  // Clock (pin 2)
#define QH_PIN   19  // Serial Data Out (pin 9)

void setup() {
  pinMode(PL_PIN, OUTPUT);
  pinMode(CP_PIN, OUTPUT);
  pinMode(QH_PIN, INPUT);

  digitalWrite(PL_PIN, HIGH);  // Start in inactive state
  digitalWrite(CP_PIN, LOW);   // Start clock low

  Serial.begin(115200);
}

void loop() {
  byte buttonBytes[4] = {0};

  // Latch parallel button states into 74HC165
  digitalWrite(PL_PIN, LOW);
  delayMicroseconds(5);
  digitalWrite(PL_PIN, HIGH);

  // Read 4 bytes (32 bits) from shift registers
  for (int i = 0; i < 4; i++) {
    buttonBytes[i] = shiftIn(QH_PIN, CP_PIN, MSBFIRST);
  }

  // Print button states (inverted: 0 = pressed, 1 = not pressed)
  Serial.print("Button States: ");
  for (int i = 0; i < 28; i++) {
    bool isPressed = (bitRead(buttonBytes[i / 8], 7 - (i % 8)) == 0);  // Active-low logic
    Serial.print(isPressed ? "1" : "0");  // 1 = pressed
    Serial.print(" ");
  }
  Serial.println();

  delay(500);
}