Multitasking_millis_ESP32.ino

#define LED1 LED_BUILTIN
#define LED2 23

unsigned long last1, last2;

void setup() {
  pinMode(LED1, OUTPUT);
  pinMode(LED2, OUTPUT);
}

void loop() {
  if (millis() - last1 >= 500) {
    last1 = millis();
    digitalWrite(LED1, !digitalRead(LED1));
  }
  if (millis() - last2 >= 300) {
    last2 = millis();
    digitalWrite(LED2, !digitalRead(LED2));
  }
}