#define LED_PIN_1 33
#define LED_PIN_2 5

hw_timer_t *Timer0_Cfg = NULL;
bool toggleState = false;

void IRAM_ATTR Timer0_ISR()
{
    toggleState = !toggleState;
    digitalWrite(LED_PIN_1, toggleState);
    digitalWrite(LED_PIN_2, !toggleState);
}

void setup()
{
    pinMode(LED_PIN_1, OUTPUT);
    pinMode(LED_PIN_2, OUTPUT);

    Timer0_Cfg = timerBegin(0, 80, true);
    timerAttachInterrupt(Timer0_Cfg, &Timer0_ISR, true);
    timerAlarmWrite(Timer0_Cfg, 1000, true);
    timerAlarmEnable(Timer0_Cfg);
}

void loop()
{
    // Do Nothing!
}