Hbridge.ino

int enablePin= 5; 
int ctrl1 = 3;
int ctrl2 = 2;
int button = 4;

int rotDirection = 1;
int buttState = false;
int preState = false;

void setup() {
  pinMode(enablePin, OUTPUT);
  pinMode(ctrl1, OUTPUT);
  pinMode(ctrl2, OUTPUT);
  pinMode(button, INPUT);
  // Set initial rotation direction
  digitalWrite(ctrl1, LOW);
  digitalWrite(ctrl2, HIGH);
}
void loop() {
  int potVal = analogRead(A0); // Read sensor value

  analogWrite(enablePin, potVal/4); // Send PWM signal to H-Bridge

  buttState = digitalRead(button);

  // check if button has changed state
  if (buttState == true && preState == false) {
    rotDirection *= -1;
  }
  
  if (rotDirection == 1) {
    digitalWrite(ctrl1, HIGH);
    digitalWrite(ctrl2, LOW);
    delay(20);
  }

  if (rotDirection == -1) {
    digitalWrite(ctrl1, LOW);
    digitalWrite(ctrl2, HIGH);
    delay(20);
  }
  
  preState = buttState;
}