PeriodicTask simulates a thread that executes a task at prescribed intervals. Its timing is based on either millis() or micros(), of which unit can be set at construct time, millis is the default. It handles rollovers automatically using the technique described in http://arduino.cc/playground/Code/TimingRollover

To use, inherit from your class that will perform the task. This class must then implement the doTask() function, where it does its work. Lastly, in order for the task to be executed, you must call myTask.run() each time in your loop() function.

Examples:

Timer to run every 10ms:

class MyTask : public PeriodicTask {
public:
    MyTask() : PeriodicTask(10) {} // do task every 10 ms

    virtual void init() { PeriodicTask::doInit(); } // you must call this in your setup() func

    virtual void run() {} // (optional) - but do call this once each time in your loop() func; we overrode it so we can call SoftPWM run for our led

    protected:
    virtual void doTask(); // here is where you will do your task
};

MyTask mytask;

void setup()
{
    myTask.init();
}

void loop()
{
    myTask.run();
}

Here's a one-shot timer. To use it, simply enable it.

class OneShotTimer : public PeriodicTask {
    OneShotTimer() : PeriodicTask(500) {}

    virtual void init() { PeriodicTask::doInit(); disableTask(); } // you must call this in your setup() func

    protected:
    virtual void doTask() { disableTask(); } // we are done now - one shot timer
};

OneShotTimer timer;

// in setup/init()
timer.init();

// in loop/run()
timer.run();

// start timer
timer.enableTask(true);