A timer in a function

[bojan_jurca]

@rainman

#define PinLed  6

bool xBlinkOn;

void Test();

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

void loop() {
  Test(millis(), &xBlinkOn);

  digitalWrite(PinLed, xBlinkOn);
}

void Test(unsigned long time , bool* xOutput){
  unsigned long timeBlink;
  bool xInit; 

  if (xInit== 0)
  {
    timeBlink = time;
    xInit = 1;
  }

  if ( time - timeBlink >= 500) 
  {
    *xOutput = !*xOutput;
    timeBlink = time;
  }
} //Test

Use 'static' variable to initialize and preserve its value through separate function calls.

#define PinLed  21

bool xBlinkOn;

void Test();

void setup() {
  Serial.begin (115200);
  pinMode(PinLed, OUTPUT | INPUT);
  xBlinkOn = digitalRead(PinLed); // or 0 or 1
}

void loop() {
  Test(millis(), &xBlinkOn);

  digitalWrite(PinLed, xBlinkOn);
}

void Test(unsigned long time , bool* xOutput){
  static unsigned long lastTimeBlink = 0;

  if ( time - lastTimeBlink >= 500) 
  {
    *xOutput = !*xOutput; 
    Serial.println (*xOutput);
    lastTimeBlink = time;
  }
} //Test