蓝牙小车想加上PWM,不会改.

ddsqr

蓝牙小车想加上PWM控制车速，串口要收前进(F)和200(PWM),请问要怎样改？
[mw_shl_code=c,true]void Forward()
{
  analogWrite(MotorLeftEn, 255);
  digitalWrite(MotorLeftA, HIGH);
  digitalWrite(MotorLeftB, LOW);
  analogWrite(MotorRightEn, 255);
  digitalWrite(MotorRightA, HIGH);
  digitalWrite(MotorRightB, LOW);
  Serial.println("Forward");
}
void loop()
{
  while(Serial.available()>0)
  {
    char val = Serial.read();
    if(val == 'f'){
      Forward();
      delay(20);  
    }
}[/mw_shl_code]