Question

FOR ARDUINO PROGRAMMING

NEED TO HAVE ALL LEDS FLASH 5 TIMES WHEN THE BOARD STARTS.

Answer 1

I think you want the flashes to stop after 5 on/off repetitions or to have 5 seconds between the flash sequences.

You need to have a variable to count the number of flashes and only increment that variable when a flash actually happens. When the 5 flashes are completed your code will know not to flash anymore.

const byte ledPin = 13;
byte flashCount = 0;
byte state = 0;
unsigned long waitStart;
unsigned long shortPeriod = 500;
unsigned long longPeriod = 5000;
unsigned long currentTime;

void setup()
{
  Serial.begin(115200);
  pinMode(ledPin, OUTPUT);
  digitalWrite(ledPin, HIGH);
  waitStart = millis();
}

void loop()
{
  switch (state)
  {
    case 0:
      currentTime = millis();
      if (currentTime - waitStart >= shortPeriod)
      {
        digitalWrite(ledPin, !digitalRead(ledPin));
        waitStart = currentTime;
        flashCount++;
        if (flashCount == 10)
        {
          state = 1;
        }
      }
      break;
      
    case 1:
      currentTime = millis();
      if (currentTime - waitStart >= longPeriod)
      {
        waitStart = currentTime;
        flashCount = 0;
        state = 0;
      }
      break;
  }
}