const int ledPin = 13;
void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  Serial.println("Hello, STM32!");
  pinMode(ledPin, OUTPUT);
  
}

void loop() {
if (readchar > 1){
  Serial.println("HALT STOP");
  digitalWrite(ledPin, LOW);
}
if (Serial.available()) {
  char readchar = Serial.read();

  if (readchar == 'a')
  {
    digitalWrite(ledPin, HIGH);
    delay(1000);
    digitalWrite(ledPin, LOW);
    delay(1000);
    digitalWrite(ledPin, HIGH);
    delay(1000);
    digitalWrite(ledPin, LOW);
    delay(1000);
  }
  else {
    digitalWrite(ledPin,LOW);
  }
}
}