+enum event_type { BUTTONPRESS, SEND };
+typedef struct {
+ enum event_type type;
+ union {
+ struct {
+ uint32_t timestamp;
+ } buttonpress;
+ struct {
+ uint32_t timestamp;
+ u16_t seq;
+ u8_t send_count;
+ } send;
+ };
+} 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 = BUTTONPRESS;
+ e.buttonpress.timestamp = now;
+ queue_try_add_ignoring_errors(&queue, &e);
+ }
+}
+