#include <Servo.h>

Servo myservo;  // create servo object to control a servo


bool increase; // = true; //flag to keep track of direction of sweep
int numberSweep(int interval, int start, int end) {
  static unsigned long previousMillis = 0; //keep track of time
  unsigned long currentMillis = millis(); //get current time
  
  if (currentMillis - previousMillis >= interval) { //check if interval has passed
    previousMillis = currentMillis; //update previous time
    static int currentValue = start; //keep track of current value

    //check if current value has reached end
    if (currentValue >= end) {
      increase = false;
    } 
    //check if current value has reached start
    else if (currentValue <= start) {
      increase = true;
    }

    //increment or decrement current value based on flag
    if (increase) {
      currentValue++;
    } 
    else {
      currentValue--;
    }
    
    return currentValue;
  }
}


void setup() {
  myservo.attach(9);  // attaches the servo on pin 9 to the servo object
  Serial.begin(115200);
}

void loop() {
  int number = numberSweep(1, 600, 2400);
  myservo.writeMicroseconds(number);
  Serial.println(number);
}