/* Komunikasi Serial — kirim & terima data */ int counter = 0;String pesan; void setup() {  Serial.begin(9600);       // buka komunikasi serial} void loop() {  Serial.print("Hello Arduino! #");  Serial.println(counter);  counter++;   if (Serial.available() > 0) {    pesan = Serial.readString();    Serial.print("Diterima: ");    Serial.println(pesan);  }   delay(1000);}