spresense Arduino IDE timer interrupt

 void attachTimerInterrupt(unsigned int(*isr)(void), unsigned intus);
// Parameter:
//   isr:the function to call when the timer interrupt occurred.
//        This function must return the next timer period [microseconds].
//        If this function returns 0, the timer stops and it has been as one shot timer.
//   us —microseconds.
//       The maximum value is about 26 seconds and if it exceeds, an error occurred.
// Note:
//   This can not be used at the same time with tone().

#define INTERVAL 100

static unsigned long counter = 0;

unsigned int callback_func(){
  Serial.print("callback_funcalled");
  Serial.print(++counter);
  Serial.println("times");
  return INTERVAL;
}

void setup() {
  Serial.begin (115200);
  attachTimerInterrupt(callback_func, INTERVAL);
}

void loop() {

}