#define LedPin 11

String Read, myString;
int PWM;

void setup() {
  pinMode(LedPin, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  if (Serial.available()){ // If there's available Serial Data
    Read = Serial.readString(); // Read it as string
    Read.substring(0, "\n"); // Reading from the first index to the end of the Command line
    if(Read.indexOf(0) == "F" || Read.indexOf(0) == "f"){
    PWM = Read.substring(1, "\n").toInt(); //Reading the PWM and Turning it into ints
    digitalWrite(LedPin, PWM);
    }
    else if (Read.indexOf(0) == "B" || Read.indexOf(0) == "b"){
      digitalWrite(LedPin, LOW);
    }
  }
}