/* Software-timer CALLBACK demo (Wokwi, ST Nucleo-C031C6)
 *
 * A FreeRTOS SOFTWARE TIMER fires beat() every 500 ms. The timer-service task
 * "calls back" your function on a schedule — no hardware, no polling loop.
 * Same callback idea as the button/ISR demo, but triggered by TIME, not a pin.
 *
 * REQUIRES: "STM32duino FreeRTOS" (Library Manager) AND configUSE_TIMERS == 1 in that
 * library's FreeRTOSConfig.h. If the build fails with "undefined reference to
 * xTimerCreate", timers are OFF in your build -> use sketch-fallback-ticker.ino instead.
 * No wiring needed (Serial + on-board LED only).
 */
#include <STM32FreeRTOS.h>

#define LED_PIN LED_BUILTIN   /* on-board LED (PA5) */
static uint32_t beats = 0;

void beat(TimerHandle_t t) {          /* <-- THE CALLBACK. Keep it short; never block here. */
  (void)t;
  beats++;
  digitalWrite(LED_PIN, !digitalRead(LED_PIN));
  Serial.print("timer callback fired, beat #"); Serial.println(beats);
}

void setup() {
  Serial.begin(115200);
  pinMode(LED_PIN, OUTPUT);

  TimerHandle_t hb = xTimerCreate(
      "heartbeat",              /* name                    */
      pdMS_TO_TICKS(500),       /* period: 500 ms          */
      pdTRUE,                   /* auto-reload -> periodic  */
      NULL,                     /* timer ID (unused)       */
      beat);                    /* the callback function   */
  xTimerStart(hb, 0);           /* arm it                  */

  vTaskStartScheduler();        /* the timer service task now runs beat() on schedule */
}

void loop() {}                  /* empty on purpose — the callback does the work */