Question

What is the easiest and simplest way to create a decrementing timer in seconds?

Im using an 8bit microcontroller and cannot use float points or intensive processes. I need a very efficient timer.

Answer 1

time(2) is a standard C function for obtaining the current time in seconds since the epoch (midnight on January 1, 1970 UTC). To make a decrementing timer, you could do something like this:

time_t startTime = time(NULL);

time_t timerDuration = 10;  // 10 second timer
time_t endTime = startTime + timerDuration;
while(1)
{
    time_t currTime = time(NULL);
    time_t timeLeft = endTime - currTime;

    if(timeLeft < 0)
    {
        // timer has finished
        break;
    }

    // do stuff - preferably don't spin at 100% CPU
}

If you need more precision than 1-second increments, you can use a platform-specific function such as gettimeofday(3) (POSIX) or GetLocalTime (Windows).