void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  Serial.println("Hello, STM32!");
  pinMode(D2, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
  delay(10); // this speeds up the simulation
  digitalWrite(D2, HIGH);  // 点亮LED
  delay(1000);              // 延迟1秒
  digitalWrite(D2, LOW);   // 熄灭LED
  delay(1000);
}