uint8_t received_buffer_First[3];
uint8_t received_buffer_Lenght[3];
uint8_t received_buffer_Command[3];
uint8_t received_buffer_CheckSUM[3];
uint8_t received_buffer_Data[256];
uint8_t Process_Buffer[256];

size_t new_timer = 0;
size_t old_timer = 0;
bool isOnTX = false, mil_looper = true;

void setup() {
  Serial.begin(115200);
}

void loop() {
  // put your main code here, to run repeatedWly:
  new_timer = millis();
  old_timer = new_timer;
  Serial.print("first of the loop  ");

  Serial.println(old_timer);

  while (mil_looper) {
    new_timer = millis();
    if (((new_timer - old_timer) < 3000)) {
      Serial.print("miliseconds before ");
      Serial.println(new_timer - old_timer);

      if ((new_timer - old_timer) >= 2500) {
        Serial.println("received_buffer_First, 1");
        Serial.print("First Byte 0x");
        Serial.println("received_buffer_First[0], HEX");
        break;  //? SERİAL BİTTİ DÖNGÜDEN ÇIKILSIN
      }
    }
  }
  delay(200);
}