#define TOGGLE 23
#define TP 22
hw_timer_t *My_timer = NULL;
portMUX_TYPE timerMux = portMUX_INITIALIZER_UNLOCKED;

void IRAM_ATTR onTimer() {
  portENTER_CRITICAL_ISR(&timerMux);
  digitalWrite(TOGGLE, !digitalRead(TOGGLE));
  digitalWrite(TP, HIGH);
  delayMicroseconds(50);
  digitalWrite(TP, LOW);
  portEXIT_CRITICAL_ISR(&timerMux);
}
void setup() {
  pinMode(TOGGLE, OUTPUT);
  pinMode(TP, OUTPUT);
  My_timer = timerBegin(0, 80, true);
  timerAttachInterrupt(My_timer, &onTimer, true);

  // My_timer on pin 23 (TOGGLE) should transition every 1000 μs (1 ms)
  // and provide a 500 Hz square wave output.
  // However, the simulated output has 2000 μs transition time,
  // presulting in a 250 Hz squarewave output.
  timerAlarmWrite(My_timer, 1000, true);
  timerAlarmEnable(My_timer);
}
void loop() {
  //delay(10);
}

// For comparison, the PWM Breakout chip is set to 1 kHz, 10% duty and
// produces the expected frequency and duty.

// A test using real ESP32 hardware was not made.