Merge pull request #20911 from fabian18/pr/event_periodic_no_delay

sys/event: add API to start periodic event without initial delay

sys/event/periodic.c

@@ -25,7 +25,6 @@
 static bool _event_periodic_callback(void *arg)
 {
     event_periodic_t *event_periodic = (event_periodic_t *)arg;
-
     event_post(event_periodic->queue, event_periodic->event);
 
     if (event_periodic->count && --event_periodic->count == 0) {

sys/include/event/periodic.h

@@ -72,6 +72,28 @@ typedef struct {
 void event_periodic_init(event_periodic_t *event_periodic, ztimer_clock_t *clock,
                          event_queue_t *queue, event_t *event);
 
+/**
+ * @brief   Starts a periodic timeout without delay for the first occurrence
+ *
+ * This will make the event as configured in @p event_periodic be triggered
+ * at every interval ticks (based on event_periodic->clock).
+ *
+ * @note: the used event_periodic struct must stay valid until after the timeout
+ *        event has been processed!
+ *
+ * @note: this function does not touch the current count value.
+ *
+ * @note: the periodic event will start without delay.
+ *
+ * @param[in]   event_periodic   event_timout context object to use
+ * @param[in]   interval         period length for the event
+ */
+static inline void event_periodic_start_now(event_periodic_t *event_periodic, uint32_t interval)
+{
+    event_periodic->timer.interval = interval;
+    ztimer_periodic_start_now(&event_periodic->timer);
+}
+
 /**
  * @brief   Starts a periodic timeout
  *

sys/include/ztimer/periodic.h

@@ -130,6 +130,19 @@ void ztimer_periodic_init(ztimer_clock_t *clock, ztimer_periodic_t *timer,
  */
 void ztimer_periodic_start(ztimer_periodic_t *timer);
 
+/**
+ * @brief    Start or restart a periodic timer without initial timer delay
+ *
+ * When called on a newly initialized timer, the timer will start.
+ *
+ * When called on an already running timer, the current interval is reset to its
+ * start (thus the next callback will be called after the configured interval
+ * has passed).
+ *
+ * @param[in]   timer   periodic timer object to work on
+ */
+void ztimer_periodic_start_now(ztimer_periodic_t *timer);
+
 /**
  * @brief   Stop a periodic timer
  *

sys/ztimer/periodic.c

@@ -75,6 +75,11 @@ void ztimer_periodic_start(ztimer_periodic_t *timer)
     timer->last = ztimer_set(timer->clock, &timer->timer, timer->interval) + timer->interval;
 }
 
+void ztimer_periodic_start_now(ztimer_periodic_t *timer)
+{
+    timer->last = ztimer_set(timer->clock, &timer->timer, 0);
+}
+
 void ztimer_periodic_stop(ztimer_periodic_t *timer)
 {
     ztimer_remove(timer->clock, &timer->timer);

tests/sys/event_ztimer/main.c

@@ -64,10 +64,9 @@ static void callback_4times(void *arg)
     uint8_t *count = (uint8_t *)arg;
 
     *count = *count + 1;
-    uint32_t now = event_periodic.timer.last;
+    uint32_t now = ztimer_now(ZTIMER_USEC);
     uint32_t elapsed = now - before;
     before = now;
-    expect((elapsed) >= 1 * US_PER_SEC);
     if (*count <= 4) {
         printf("trigger %d of periodic timeout, elapsed time: %" PRIu32 " us\n",
                *count, elapsed);
@@ -110,8 +109,15 @@ int main(void)
     event_periodic_init(&event_periodic, ZTIMER_USEC, EVENT_PRIO_MEDIUM,
                         &event_4times.super);
     event_periodic_set_count(&event_periodic, 4);
+    before = ztimer_now(ZTIMER_USEC);
     event_periodic_start(&event_periodic, EVENT_TIMEOUT_TIME);
-    before = event_periodic.timer.last;
+    puts("waiting for periodic callback to be triggered 4 times");
+    mutex_lock(&lock);
+    puts("posting periodic timed callback with timeout 1sec and no delay");
+    event_periodic_set_count(&event_periodic, 4);
+    iter = 0; /* reset callback argument counter to 0 */
+    before = ztimer_now(ZTIMER_USEC);
+    event_periodic_start_now(&event_periodic, EVENT_TIMEOUT_TIME);
     puts("waiting for periodic callback to be triggered 4 times");
     mutex_lock(&lock);
     puts("posting timed callback with timeout 0.5sec, clear right after");