#include <Servo.h>

Servo ESC;

const byte
IN1 = 4,
IN2 = 5,
IN3 = 6,
IN4 = 7,
MotorPin = 8
;

void setup ()
{
  pinMode ( IN1, INPUT_PULLUP );
  pinMode ( IN2, INPUT_PULLUP );
  pinMode ( IN3, INPUT_PULLUP );
  pinMode ( IN4, INPUT_PULLUP );
  ESC.attach ( MotorPin, 1000, 2000 );
}

void loop ()
{
  if ( digitalRead ( IN1 ) == LOW )
  {
    ESC.write ( 45 ); // 1/4 speed
  }
  else if ( digitalRead ( IN2 ) == LOW )
  {
    ESC.write ( 90 ); // 1/2 speed
  }
  else if ( digitalRead ( IN3 ) == LOW )
  {
    ESC.write ( 135 ); // 3/4 speed
  }
  else if ( digitalRead ( IN4 ) == LOW )
  {
    ESC.write ( 180 ); // full speed
  }
  else
  {
    ESC.write ( 0 ); // stand still
  }
}