#define LED1 33
#define LED2 25
 
hw_timer_t *Timer0_Cfg = NULL;
 
void IRAM_ATTR Timer0_ISR()
{
    digitalWrite(LED1, !digitalRead(LED1));
     digitalWrite(LED2, !digitalRead(LED2));
}
void setup()
{
    pinMode(LED1, OUTPUT);
    pinMode(LED2, OUTPUT);
    Timer0_Cfg = timerBegin(0, 80, true);
    timerAttachInterrupt(Timer0_Cfg, &Timer0_ISR, true);
    timerAlarmWrite(Timer0_Cfg, 1000000, true);
    timerAlarmEnable(Timer0_Cfg);
}
void loop()
{
    // Do Nothing!
}