byte lastData = 0;

void setup() {
  Serial.begin(9600);

  int pins[] = {A0,A1,A2,A3,A4,A5,2,3};
  for (int i = 0; i < 8; i++) {
    pinMode(pins[i], INPUT_PULLUP);
  }
}

void loop() {
  byte data = 0;
  int pins[] = {A0,A1,A2,A3,A4,A5,2,3};

  for (int i = 0; i < 8; i++) {
    if (digitalRead(pins[i]) == LOW) {
      data |= (1 << i);
    }
  }

  if (data != lastData) {   // فقط در صورت تغییر
    Serial.write(data);
    lastData = data;
  }

  delay(50);
}