// This example makes a led connected to analog output (PWM) pin 3 fade in
// and out, by changing its voltage between 0V and 5V.
// In Arduino a maximum output value of 255 corresponds to output voltage 5V.

#define pinPWM 3                  // analog output (PWM) pin with connected led

int v = 0;                        // analog output value
int s = 5;                        // speed of fading

void setup() {
}

void loop() {
  v += s;                         // change v with step s
  if ((v < 0) || (v > 255)) {     // if v outside its value range, then
    s *= -1;                      //   reverse direction of fading
    v += s;                       //   restore v to within value range
  }
  analogWrite(pinPWM, v);         // set PWM pin a to value v
  delay(10);
}