+enum event_type { NEW_BUTTON_PRESS, RESEND_TIME };
+typedef struct {
+ enum event_type type;
+ union {
+ struct {
+ uint32_t timestamp;
+ } buttonpress;
+ };
+} event_t;
+
+queue_t queue;
+
+uint32_t time_s() { return time_us_64() / 1000000ul; }
+
+/* Often we don't bother checking for failure (full queue) because
+ * 1. The best thing to do in this unfortunate situation is to blithely
+ * continue, dropping some events; continuing is better than stopping.
+ * 2. Neither interrupt context nor queue-processing context can block
+ * until space is available, or even sit around & blink the LED to
+ * signal a problem.
+ * (We also get a bit of type safety by taking event_t* rather than void*.) */
+static void queue_try_add_ignoring_errors(queue_t *q, event_t *e) {
+ queue_try_add(q, e);
+}
+
+static void button_pressed() {
+ /* This runs in interrupt context; don't linger. */
+ static uint64_t last_button_press_time = 0;
+ uint32_t now = time_s();
+ uint32_t time_since_last_press = now - last_button_press_time;
+ if (time_since_last_press >= config_minimum_seconds_between_button_presses) {
+ last_button_press_time = now;
+ event_t e;
+ e.type = NEW_BUTTON_PRESS;
+ e.buttonpress.timestamp = now;
+ queue_try_add_ignoring_errors(&queue, &e);
+ }
+}
+
+static void time_to_send(uint _) {
+ /* This runs in interrupt context; don't linger. */
+ event_t e;
+ e.type = RESEND_TIME;
+ queue_try_add_ignoring_errors(&queue, &e);
+}
+
+void set_resend_alarm(int alarm, uint32_t now, uint32_t next_act_time) {
+ uint32_t sleep_duration = next_act_time - now;
+ if (hardware_alarm_set_target(alarm,
+ make_timeout_time_ms(sleep_duration * 1000)))
+ signal_error_by_blinking();
+ return;
+}
+
+void service_sleeps(int alarm, press_pile_t *pp) {
+ hardware_alarm_cancel(alarm);
+
+ while (1) {
+ uint32_t now = time_s();
+ int32_t act_time = next_scheduled_send(pp);
+ if (act_time == -1)
+ return;
+ if (act_time > now) {
+ set_resend_alarm(alarm, now, act_time);
+ return;
+ }
+ pheap_node_id_t i = ph_remove_head(pp->sleeps_heap, false);
+ press_t *press = &pp->presses[i];
+ uint32_t ago = now - press->timestamp;
+ send_report_packet(press->seq, ago);
+ press->send_count++;
+ if (press->send_count < config_resend_count)
+ ph_insert_node(pp->sleeps_heap, i);
+ else
+ ph_free_node(pp->sleeps_heap, i);
+ }
+}
+
+void service_queue() {
+ int alarm = hardware_alarm_claim_unused(true);
+ if (alarm == -1)
+ signal_error_by_blinking();
+ hardware_alarm_set_callback(alarm, time_to_send);
+
+ press_pile_t *pp = create_press_pile();
+ u16_t seq = 0;
+ while (1) {
+ service_sleeps(alarm, pp);
+
+ event_t e;
+ queue_remove_blocking(&queue, &e);
+ switch (e.type) {
+ case NEW_BUTTON_PRESS: {
+ add_press(pp, &(press_t){e.buttonpress.timestamp, seq++, 0});
+ } break;
+ case RESEND_TIME: {
+ /* OK, we're awake. Cool. Thanks! (We actually do the sends in the
+ * service_sleeps() call at the top of the loop.) */
+ } break;
+ default:
+ signal_error_by_blinking();
+ }
+ }
+}