int led = 10;
float frequency = 440;
float timeDelay = (1/frequency)*500000;
String inString = "";

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


}

void loop(){
 // Read serial input:
  while (Serial.available() > 0) {
    int inChar = Serial.read();
    if (isDigit(inChar)) {
      // convert the incoming byte to a char and add it to the string:
      inString += (char)inChar;
    }
    // if you get a newline, print the string, then the string's value:
    if (inChar == '\n') {
     frequency = inString.toInt();
     frequency = map(frequency,10,100,100,400);
     frequency = (float) frequency;
     timeDelay = (1/frequency)*500000;
     inString = "";
    }



  }



        digitalWrite(led,HIGH);
        delayMicroseconds(timeDelay);
        digitalWrite(led,LOW);
        delayMicroseconds(timeDelay);
}