1 /*
   2  Author    : Loe Feijs
   3  Date      : 20130302
   4  
   5  This example shows how to control a LED (LED via 470 Ohm 
   6  between pin 9 and GND). The light goes on when the button 
   7  switch is pushed. Switch between GND and pin 2. The light 
   8  source goes off after 4 seconds (programmed as a finite 
   9  state machine).
  10  */
  11 
  12 //connect LED, Button:
  13 #define ledPin 9 
  14 #define buttonPin 2
  15 
  16 //FSM states:
  17 #define OFF 0
  18 #define ON  1
  19 
  20 // initialisation
  21 int state = OFF;
  22 int timer = 0;
  23 
  24 void setup()  { 
  25   pinMode(ledPin, OUTPUT); 
  26   pinMode(buttonPin, INPUT_PULLUP);
  27 } 
  28 
  29 void loop()  { 
  30   LEDstep();
  31   delay(10); // one step every 10 ms
  32 }
  33 
  34 /*
  35 Finite state machine implementation
  36  */
  37 void LEDstep(){
  38 
  39   switch (state){
  40   case OFF:
  41     if (digitalRead(buttonPin) == LOW){
  42       // change state
  43       state = ON;
  44       // state transition actions
  45       timer = 400; // 10 millisecond steps 
  46       analogWrite(ledPin,255); // max brightness
  47     }  
  48     break;
  49   case ON: 
  50     if (timer <= 0){
  51       // change state
  52       state = OFF;
  53       // state transition actions
  54       analogWrite(ledPin,0);
  55     } 
  56     else timer--;
  57     break;
  58   }
  59 }