Non-blocking strobing code?

Timers are the best way to go, (much) less overhead and you don't have to worry about it elsewhere in your code (other than managing variable use between your main loop and your ISRs).

But I do have a habit of doing things the hard way in code first and then move to timers once I've got it the way I'd like.

Here is sample code to flash the on board LED X times per second, I have calculated it to mean, ON 7 times per second and OFF 7 times as well (meaning, there is a change of state 14 times per second).

This code isn't efficient, it doesn't take into consideration that the value is already set or not, it just writes the value that it should be right now.

Finally, to go to analogWrite and use PWM, just change:

digitalWrite(LED, HIGH);

to

analogWrite(NEW_PIN, PWM_VALUE);

code:

#define LED               13
#define TIMES_PER_SECOND  7

const int M1 = 1000 / TIMES_PER_SECOND;
const int M2 = 1000 / TIMES_PER_SECOND / 2;

void setup(){
  pinMode(LED,OUTPUT);
}

void loop(){
  if(millis()%M1<M2){
    digitalWrite(LED, HIGH);
  } else {
    digitalWrite(LED, LOW);
  } 
}

Remember there is overhead with digital (and analog) writes, so (as I mentioned) you could check to see if the value is set already or not and skip the write.