const int switchPin = 2;    // switch input
  const int motor1Pin = 3;    // H-bridge leg 1 (pin 2, 1A)
  const int motor2Pin = 4;    // H-bridge leg 2 (pin 7, 2A)
  const int enablePin = 9;    // H-bridge enable pin
  
  
  void setup() {
   
     // initialize serial:
  Serial.begin(9600);
   
    // set the switch as an input:
    pinMode(switchPin, INPUT); 

    // set all the other pins you're using as outputs:
    pinMode(motor1Pin, OUTPUT); 
    pinMode(motor2Pin, OUTPUT); 
    pinMode(enablePin, OUTPUT);


    // set enablePin high so that motor can turn on:
    digitalWrite(enablePin, HIGH); 
  }
  
  
    void loop() {
      
      
      while (Serial.available() >0) {
        
        int thespeed = Serial.parseInt();
        int thedirection = Serial.parseInt();
        
        if (Serial.read() == '\n') {
          
          thespeed = 255 - constrain(thespeed, 0, 255);
          thedirection = 255 - constrain(thedirection, 0, 255);
         
         analogWrite(enablePin,thespeed); 
          
        }
    
      }
      
      
      
    // if the switch is high, motor will turn on one direction:
    if (digitalRead(switchPin) == HIGH) {
      digitalWrite(motor1Pin, LOW);   // set leg 1 of the H-bridge low
      digitalWrite(motor2Pin, HIGH);  // set leg 2 of the H-bridge high
    } 
    // if the switch is low, motor will turn in the other direction:
    else {
      digitalWrite(motor1Pin, HIGH);  // set leg 1 of the H-bridge high
      digitalWrite(motor2Pin, LOW);   // set leg 2 of the H-bridge low
    }
  }