Waiter class

This class lets you do a non-blocking delay (so the Arduino can continue to execute other code)

waiter.h

typedef uint32_t clock_t;
const clock_t INFINITE = ( (clock_t)(-1) );
const clock_t SEC = 1000;
 
//
// waiter: returns true and resets if more than time has passed
//
class waiter {
    clock_t last;
public:
    waiter() : last(millis()) {}
    bool wait( const clock_t time ) {
        clock_t now = millis();
        if( now - last >= time ) {
            last = now;
            return true;
        }
        return false;
    };
};

For example, to flash an LED:

flash.pde

#include <waiter.h>
 
const byte ledPin = 13;
const clock_t flashTime = 2 * SEC;
 
waiter ledFlash;
bool ledState;
 
void setup() {
    pinMode( ledPin, OUTPUT );
};
 
void loop() {
    if( ledFlash.wait( flashTime ) ) {
        ledState = !ledState;
        digitalWrite( ledPin, ledState );
    }
};

You can reset the timer with:

ledFlash.wait( 0 );