void setup() {
  pinMode(2, OUTPUT);
  Serial.begin(115200);
  Serial.println("Hello, ESP32!");
}

void loop() {
 if(Serial.available())
 {
  char signal = Serial.read() - '0';
  if(signal) digitalWrite(2, HIGH);
  else digitalWrite(2, LOW);
 }
 delayMicroseconds(100);
}