void setup()
{
  Serial.begin(115200);
  OCR0A = 50;
  DDRD |= (1 << PD6);
  TCCR0A = 0b10000011;
  TCCR0B = 0b00000100;
}

void loop()
{
  for (int i = 0; i < 255; ++i)
  {
    OCR0A = i;
    Serial.print("Motor velocity: ");
    Serial.println(analogRead(A0));
    delay(10);
  }

  for (int i = 255; i > 0; --i)
  {
    OCR0A = i;
    Serial.print("Motor velocity: ");
    Serial.println(analogRead(A0));
    delay(10);
  }
}