drv/bluetooth_btstack: Avoid broadcast in tight loop.

Fixes pybricks/support#1151

CHANGELOG.md

@@ -23,10 +23,13 @@
 - Fixed `surface=False` not working in `ColorSensor` ([support#1232]).
 - Fixed `PUPDevice.write` not selecting correct mode ([support#1213]).
 - Fixed City Hub turning back on after shutdown ([support#1195]).
+- Fixed SPIKE hubs not broadcasting at all when attempting to broadcast in a
+  tight loop ([support#1151]).
 
 [pybricks-micropython#104]: https://github.com/pybricks/pybricks-micropython/pull/104
 [support#1054]: https://github.com/pybricks/support/issues/1054
 [support#1140]: https://github.com/pybricks/support/issues/1140
+[support#1151]: https://github.com/pybricks/support/issues/1151
 [support#1189]: https://github.com/pybricks/support/issues/1189
 [support#1195]: https://github.com/pybricks/support/issues/1195
 [support#1213]:  https://github.com/pybricks/support/issues/1213

lib/pbio/drv/bluetooth/bluetooth_btstack.c

@@ -739,6 +739,8 @@ void pbdrv_bluetooth_disconnect_remote(void) {
 static PT_THREAD(start_broadcasting_task(struct pt *pt, pbio_task_t *task)) {
     pbdrv_bluetooth_value_t *value = task->context;
 
+    static struct timer broadcast_delay;
+
     PT_BEGIN(pt);
 
     if (value->size > LE_ADVERTISING_DATA_SIZE) {
@@ -760,6 +762,13 @@ static PT_THREAD(start_broadcasting_task(struct pt *pt, pbio_task_t *task)) {
         is_broadcasting = true;
     }
 
+    // Delay to allow for advertising to start. FIXME: This is technically only
+    // needed if a previous broadcast was started sooner than this. It would be
+    // better to conditionally await just before the broadcast so we can avoid
+    // unnecessary delays.
+    timer_set(&broadcast_delay, 10);
+    PT_WAIT_UNTIL(pt, timer_expired(&broadcast_delay));
+
     // REVISIT: use callback to actually wait for start?
     task->status = PBIO_SUCCESS;