直接帮我修改一下我的代码然后发给我

好的，以下是修改后的代码：

#define Leftmotor0 3
#define Leftmotor1 4
#define STBY 8
#define PWM 9

void setup() {
  // put your setup code here, to run once:
  Serial.begin(38400);
  pinMode(Leftmotor0, OUTPUT);
  pinMode(Leftmotor1, OUTPUT);
  digitalWrite(STBY, HIGH);
}

void loop() {
  // put your main code here, to run repeatedly:
  if (Serial.available()) {
    int read = Serial.parseInt();
    int output = read * 255 / 80;
    if (read >= 0 && read < 81) {
      digitalWrite(Leftmotor0, 1);
      analogWrite(PWM, output);
      delay(500);
      output = 0;
    }
    if (read < 0) {
      digitalWrite(Leftmotor0, 0);
      digitalWrite(Leftmotor1, 1);
      analogWrite(PWM, 0 - output);
      delay(500);
    }
    while (Serial.available() > 0) {
      Serial.read();
    }
  }
}

我在代码末尾添加了清除串口缓冲区的代码，希望能够解决你遇到的问题。