RTOS Software Timer 활용 — One-shot·Auto-reload·Daemon Task

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HW timer        peripheral 한 개 = timer 한 개, µs 정밀
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SW timer        timer task 한 개 = N개 가상 timer, tick 정밀(보통 1 ms)

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TimerHandle_t inactivity;
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void inactivity_cb(TimerHandle_t t) {
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    screen_off();
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}
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void on_user_input(void) {
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    xTimerReset(inactivity, 0);   /* 30초 새로 셈 */
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}
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void init(void) {
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    inactivity = xTimerCreate(
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        "idle",
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        pdMS_TO_TICKS(30000),
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        pdFALSE,            /* one-shot */
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        NULL,
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        inactivity_cb);
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    xTimerStart(inactivity, 0);
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}

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TimerHandle_t heartbeat;
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void hb_cb(TimerHandle_t t) {
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    static int phase;
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    led_set(phase ^= 1);
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    watchdog_ping();
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}
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void init(void) {
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    heartbeat = xTimerCreate(
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        "hb",
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        pdMS_TO_TICKS(500),
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        pdTRUE,             /* auto-reload */
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        NULL,
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        hb_cb);
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    xTimerStart(heartbeat, 0);
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}

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TimerHandle_t led_timers[4];
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void led_cb(TimerHandle_t t) {
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    int idx = (int)(uintptr_t)pvTimerGetTimerID(t);
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    led_toggle(idx);
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}
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void init(void) {
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    for (int i = 0; i < 4; i++) {
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        led_timers[i] = xTimerCreate("led", pdMS_TO_TICKS(100 * (i + 1)),
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                                      pdTRUE, (void *)(uintptr_t)i, led_cb);
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        xTimerStart(led_timers[i], 0);
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    }
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}

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static StaticTimer_t hb_buf;
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TimerHandle_t hb;
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void init(void) {
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    hb = xTimerCreateStatic(
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        "hb", pdMS_TO_TICKS(500),
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        pdTRUE, NULL, hb_cb, &hb_buf);
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    xTimerStart(hb, 0);
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}

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void EXTI_IRQHandler(void) {
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    BaseType_t hp = pdFALSE;
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    xTimerResetFromISR(inactivity, &hp);   /* 30s timer reset */
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    portYIELD_FROM_ISR(hp);
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}

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/* 정밀 50 µs PWM — HW timer가 답 */
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void TIM2_IRQHandler(void) {
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    pwm_update();           /* ISR에서 직접 — SW timer로는 불가능 */
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}

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void shutdown_module(void) {
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    xTimerStop(t, pdMS_TO_TICKS(100));
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    /* 이 시점 callback이 이미 실행 중일 수 있음 */
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    if (xTimerDelete(t, pdMS_TO_TICKS(100)) != pdPASS) {
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        log_err("timer delete failed");
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    }
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    /* callback이 사용하던 자원은 callback 완료 후 free */
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}

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void cb(TimerHandle_t t) {
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    xQueueReceive(q, &item, portMAX_DELAY);   /* timer task 자체가 멈춤 */
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}

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void cb(TimerHandle_t t) {
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    flash_write(buf, 4096);   /* 수십 ms — 다음 callback 늦어짐 */
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}

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xTimerStart(t, 0);   /* timer queue 가득 차면 fail */

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xTimerCreate("x", 0, pdTRUE, NULL, cb);   /* assert fail */

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xTimerDelete(t, 0);
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free(my_buf);   /* 마지막 callback이 my_buf 사용 중이면 use-after-free */