void setup() {
  pinMode(3, OUTPUT);
  pwm_init();
}

void loop() {
  // put your main code here, to run repeatedly:
  //slowly ramp up speed until it reaches the maximum value
  for(int i = 0; i < 255; i+=10) {
    setSpeed(i);
    delay(100);
  }
  delay(1000);
}

/*Initialize pwm output on pin 3
 *This function should be placed in the setup to run once
 */
void pwm_init() {
  TCCR2A |= ( _BV(COM2A1)| _BV(COM2B1) | _BV(WGM21) | _BV(WGM20) );
  TCCR2B |= ( _BV(WGM22) | _BV(CS22) | _BV(CS21) | _BV(CS22) );
  PRR &= ~_BV(PRTIM2);
  OCR2A = 124;  //min value OCR2A should be
}

/*
 * Set the speed of the motors, it will map the input into a range that the stepper motors can support
 * Motors will stop moving at a speed of 0 and increase linearly from there
 * INPUTS: 8bit number 0-255
 * OUTPUTS: None
 */
void setSpeed( uint8_t speed ) {
  //Absolute fastest it can go is 2ms
  //Speed is set by 16000000/500/1024
  if( speed == 0 ){
    OCR2A = 0;
  } else {
    int val = 0;
    val = map(speed, 0,255, 255, 124);
    OCR2A = val;
  }
}