// This example makes a led connected to analog output (PWM)
// pin 0 fade in and out, by changing the voltage between 0V
// and 5V. In Wiring a maximum output value of 1023 corresponds
// to output voltage 5V.
// For Arduino i/o boards, the analog output pins are numbered
// differently, and their output value ranges between 0 (0V)
// and 255 (5V).

int a = 0;                        // analog output pin with connected led
int v = 0;                        // analog output value
int s = 5;                        // speed of led fading


void setup() {
}


void loop() {
  v += s;                         // change v with step s
  if ((v < 0) || (v >= 1024)) {   // if v outside its value range
    s *= -1;                      // reverse direction of fading
    v += s;                       // restore v to within value range
  }
  analogWrite(a, v);              // set analog out pin a to value v
  delay(10);
}