arduino millis
unsigned long previousMillis = 0;
const long interval = 1000;
void setup(){
pinMode(LED_BUILTIN, OUTPUT);
}
void loop(){
unsigned long currentMillis = millis();
if (currentMillis - previousMillis >= interval)
{
previousMillis = currentMillis;
digitalWrite(LED_BUILTIN, !digitalRead(LED_BUILTIN));
}
}