Electric focus for my telescope

TelescopeFocus

#include <Servo.h>

/*
The buttons switch in a voltage divider so that the left and right buttons both use the same pin.
The speed controller is a potentiometer.

/*



const int DIRECTION_BUTTONS = A5;
const int SPEED_DIAL = A6;

const int FOCUS_SERVO_PIN = 2;
const int FOCUS_SERVO_CENTER_PULSE_uS = 1500;
const int FOCUS_SERVO_FULL_CLOCKWISE_PULSE_uS = 1300;
const int FOCUS_SERVO_FULL_ANTICLOCK_PULSE_uS = 1700;

const float CENTER = 90.0;

Servo focus_servo;


void setup(){
  focus_servo.attach(FOCUS_SERVO_PIN,FOCUS_SERVO_FULL_CLOCKWISE_PULSE_uS,FOCUS_SERVO_FULL_ANTICLOCK_PULSE_uS);
  //For exact calibration of the servo
  //focus_servo.writeMicroseconds(FOCUS_SERVO_CENTER_PULSE_uS);
  focus_servo.write(CENTER);
  
}

int checkButton(int which){
  int retval = 0;
  int buttonVoltage = analogRead(which);
  
  if( buttonVoltage > 300 && buttonVoltage < 600){
    retval = 1;
  }
  
  if( buttonVoltage > 700){
    retval = 2;
  }

  return retval;
}


void loop(){
  int buttonState = 0;
  float speedDial = 0;
  float maxSpeed = 5.0;
  float servoSpeed = 0.0;

  
  buttonState = checkButton(DIRECTION_BUTTONS);
  speedDial = (1024 - analogRead(SPEED_DIAL))/1023.0;
  
  
  
  if(buttonState == 0){
    focus_servo.write(CENTER);
  }else if(buttonState == 1 || buttonState == 2){
    servoSpeed = speedDial*maxSpeed;
    if( buttonState == 2){
      servoSpeed *= -1.0;
    }
    if( buttonState == 1){
      servoSpeed += 1.0;
    }
      focus_servo.write(CENTER + servoSpeed);
      
  }
  
}