const int ledPin = 13;
int ledState = LOW;
unsigned long previousMillis = 0;
unsigned long interval = 1000;
void setup() {
pinMode(ledPin, OUTPUT);
}
void loop() {
unsigned long currentMillis = millis();
if (currentMillis - previousMillis >= interval) {
previousMillis = currentMillis;
if (ledState == LOW)
ledState = HIGH;
else
ledState = LOW;
digitalWrite (ledPin, ledState);
}
}