#define STEP_PIN  2   // Step
#define DIR_PIN   5   // Direction

// With a 1024 prescaler, max step time about 4 second
//#define PRESCALER 1024

// With a 256 prescaler, max step time about 1 seconds
#define PRESCALER 256


bool motorDir = false;

String rxBuf;

// Set Timer1 interrupt frequency
void setStepDelay(float stepTime) {

  float t1Register = F_CPU / (PRESCALER * (2 / stepTime)) - 1  ;
  noInterrupts();
  TCCR1A = 0; TCCR1B = 0; TCNT1 = 0;                  // Clear registers
  OCR1A = (uint16_t) t1Register;                      // MUST be > 0 and <65536
  TCCR1B |= (1 << WGM12);                             // CTC
  TCCR1B |= (1 << CS12) | (0 << CS11) | (0 << CS10);  // Prescaler 256
  //TCCR1B |= (1 << CS12) | (0 << CS11) | (1 << CS10);    // Prescaler 1024

  TIMSK1 |= (1 << OCIE1A);                            // Output Compare Match A Interrupt Enable
  interrupts();

  Serial.print("OCR1A: ");
  Serial.println((uint16_t) t1Register);              // MUST be > 0 and <65536
}

// Timer 1 Interrupt Service Routine. If motor must run, simply toggle the state of STEP_PIN
ISR(TIMER1_COMPA_vect) {
  digitalWrite(STEP_PIN, digitalRead(STEP_PIN) ^ 1);
}


void getNewValue() {
  while (Serial.available()) {
    float newValue = Serial.parseFloat();
    if (newValue) {
      setStepDelay(newValue);
    }
  }
}



void setup()
{
  rxBuf.reserve(128);
  pinMode(DIR_PIN, OUTPUT);
  pinMode(STEP_PIN, OUTPUT);

  Serial.begin(115200);
  Serial.println("Insert a value for step time (eg. 0.01):");
  motorDir = true;
  digitalWrite(DIR_PIN, motorDir);    // Set DIR pin value
  setStepDelay(0.05); 
}

void loop()
{
  getNewValue();
}