A timer in a function

Projects Programming
3

Do you understand how this TIMER snippet works ?


  //**********************************************                h e a r t b e a t   T I M E R
  //is it time to toggle the heartbeatLED ?
  if (millis() - heartbeatTime >= 500ul)
  {
    //restart this TIMER
    heartbeatTime = millis();

    //toggle LED
    digitalWrite(heartbeatLED, digitalRead(heartbeatLED) == HIGH ? LOW : HIGH);
  }