// Delay-Free Timing 01
//
// The Arduino has a built in clock that gives out the number of 
// milliseconds the Arduino has been running since the last reset
// (it actually is a finite number, and resets to 0 after about
// 9 hours and 32 minutes). We can use this number, millis(), to
// check how long it has been since something has happened, like
// the last time an LED was turned on. This can eliminate the bottleneck
// caused by the delay() command.

// Set variables
// Set up three timers, each with a different offset to check against.
long timer1 = 0;           // Timers are measured in milliseconds, which quickly get quite large.
                           // We'll use "long" instead of "int" because int can only store a number 
                           // from -32,768 to 32,768, or + or - 2 to the 15th power, or 2 bytes.
                           // "long" extends the range to 4 bytes, or +/- 2,147,483,684
int  timer1offset = 1000;  // timer1offest will hold the length of time were using instead of a delay()                        
// Setup pins
int ledPin1 = 13;

void setup() {                  // The standard stuff...
    Serial.begin(9600);         // Setup the serial communications so we can debug
    pinMode(ledPin1, OUTPUT);  
    timer1 = millis();          // Setting the timer to the milliseconds since the board was reset
}


// Das Loop...
void loop() {
  // Timer 1
  if((timer1 + timer1offset) < millis() ) { // In other words, if timer1 plus an offset, say
                                            // 123 + 1000 is less than the current time, say 1300, 
                                            // then the timer is finished, so do something and reset
                                            // the timer to the current time
     doFlash();              // doFlash is a custom function we wrote ourselves, 
                             // as opposed to a built-in command.
     timer1 = millis();  
  }
}

// A new function!
void doFlash() {
  Serial.println(digitalRead(ledPin1)); 	// Output the status to the serial port
  digitalWrite(ledPin1, !digitalRead(ledPin1)); // This is a neat trick. "!" means "not"
  												// in Arduino language. When we say
												// !digitalRead(ledPin1) we're saying
												// "make this statement the opposite
												// of what is says"
}