const int servoPin = 9;      
int currentPos = 0;         
int stepAngle = 5;        
int speedDelay = 10;        

int angleToPulse(int angle) {
  return map(angle, 0, 180, 500, 2500);
}

void servoWrite(int angle) {
  int pulseWidth = angleToPulse(angle);
  digitalWrite(servoPin, HIGH);
  delayMicroseconds(pulseWidth);
  digitalWrite(servoPin, LOW);
  delayMicroseconds(20000 - pulseWidth);
}

void servoMove(int targetAngle) {
  targetAngle = constrain(targetAngle, 0, 180);

  int step = (targetAngle > currentPos) ? stepAngle : -stepAngle;

  while (currentPos != targetAngle) {
    currentPos += step;

    if (step > 0)
      currentPos = constrain(currentPos, 0, targetAngle);
    else
      currentPos = constrain(currentPos, targetAngle, 180);

    for (int i = 0; i < 5; i++) {
      servoWrite(currentPos);
    }
    delay(speedDelay);
  }
}

void setup() {
  pinMode(servoPin, OUTPUT);
  pinMode(A0, INPUT);  pinMode(A1, INPUT);
}
void loop() {
  int move  = map(analogRead(A0), 0, 1023, 180, 0);
  servoMove(move);
}