超小的蓝牙控制继电器

int relay=13;
int relayState = 0;
String readString;

void setup() {
  Serial.begin(9600);
  pinMode(relay,OUTPUT);
}

void loop(){
  while(Serial.available()){
    delay(3);
    char c = Serial.read();
    readString += c;
    }
    relayState = digitalRead(relay);
    if(relayState==HIGH) {
      Serial.print("");
      Serial.println("Device is ON");
      }
      else if(relayState == LOW){
      Serial.print("");
      Serial.println("Device is OFF");
      }
      delay(200);

   if(readString.length()>0){
    Serial.println(readString);
    if(readString == "on")
   {
   digitalWrite(relay,HIGH);
   }
   if(readString=="off")
  {
   digitalWrite(relay,LOW);
   }
   readString="";
   }
}
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