#define Btn1_GPIO 35
#define LED1_GPIO 5

void IRAM_ATTR Ext_INT1_ISR()
{
  //toggle the led
  digitalWrite(LED1_GPIO,!digitalRead(LED1_GPIO));
}

void setup()
{
  pinMode(LED1_GPIO, OUTPUT);
  pinMode(Btn1_GPIO, INPUT);
  attachInterrupt(Btn1_GPIO,Ext_INT1_ISR,RISING);
}
void loop()
{
  //do nothing....
}