Improves Fade to ensure PWM pin is used

Author: ocarneiro

build/shared/examples/01.Basics/Fade/Fade.ino

@@ -4,10 +4,16 @@
  This example shows how to fade an LED on pin 9
  using the analogWrite() function.
 
+ The analogWrite() function uses PWM, so if
+ you want to change the pin you're using, be
+ sure to use another PWM capable pin. On most
+ Arduino, the PWM pins are identified with 
+ a "~" sign, like ~3, ~5, ~6, ~9, ~10 and ~11.
+
  This example code is in the public domain.
  */
 
-int led = 9;           // the pin that the LED is attached to
+int led = 9;           // the PWM pin the LED is attached to
 int brightness = 0;    // how bright the LED is
 int fadeAmount = 5;    // how many points to fade the LED by
 
@@ -32,4 +38,3 @@ void loop() {
   // wait for 30 milliseconds to see the dimming effect
   delay(30);
 }
-