pbio/drv/bluetooth_stm32_cc2640: Only restart observe when needed.

Everytime we restart observing, there is a small chance of locking up the Bluetooth chip. The restart was added as a workaround for the scan queue getting full so new scan events were not coming in. This usually doesn't happen for a long time, so we can avoid restarting observing until then.

Since there isn't a good way to know if the queue is full, we can request a restart if we are not receiving data when the user is expecting some data. In the worst case, this will still restart it every 10 seconds as it used to do. If all of the subscribed channels get incoming data, restarting is delayed, thus reducing the likelihood of a freeze.

Author: laurensvalk

CHANGELOG.md

@@ -12,7 +12,12 @@
 - Extensive overhaul of UART and port drivers on all hubs. This affects all
   official LEGO sensors on all hubs.
 
+### Fixed
+- Reduced hanging when broadcasting and observing at the same time with Technic
+  Hub ([support#2206]).
+
 [support#220]: https://github.com/pybricks/support/issues/220
+[support#2206]: https://github.com/pybricks/support/issues/2206
 [pybricks-micropython#208]: https://github.com/pybricks/pybricks-micropython/pull/208
 
 ## [3.6.1] - 2025-03-11

lib/pbio/drv/bluetooth/bluetooth_stm32_cc2640.c

@@ -160,8 +160,8 @@ static const pbdrv_bluetooth_stm32_cc2640_platform_data_t *pdata = &pbdrv_blueto
 #define SCAN_RESTART_INTERVAL 3000
 #define OBSERVE_RESTART_INTERVAL 10000
 static struct etimer scan_restart_timer;
-static struct etimer observe_restart_timer;
-static bool observe_restart_enabled;
+static bool observe_restart_requested;
+static uint32_t observe_restart_time;
 
 /**
  * Converts a ble error code to the most appropriate pbio error code.
@@ -500,7 +500,6 @@ static PT_THREAD(peripheral_scan_and_connect_task(struct pt *pt, pbio_task_t *ta
 
     // temporarily stop observing so we can active scan
     if (is_observing) {
-        observe_restart_enabled = false;
 
         PT_WAIT_WHILE(pt, write_xfer_size);
         GAP_DeviceDiscoveryCancel();
@@ -747,10 +746,8 @@ static PT_THREAD(peripheral_scan_and_connect_task(struct pt *pt, pbio_task_t *ta
 
         device_discovery_done = false;
 
-        PROCESS_CONTEXT_BEGIN(&pbdrv_bluetooth_spi_process);
-        etimer_set(&observe_restart_timer, OBSERVE_RESTART_INTERVAL);
-        PROCESS_CONTEXT_END(&pbdrv_bluetooth_spi_process);
-        observe_restart_enabled = true;
+        observe_restart_time = pbdrv_clock_get_ms();
+        observe_restart_requested = false;
     }
 
     PT_END(pt);
@@ -1162,10 +1159,8 @@ static PT_THREAD(observe_task(struct pt *pt, pbio_task_t *task)) {
         device_discovery_done = false;
         is_observing = true;
 
-        PROCESS_CONTEXT_BEGIN(&pbdrv_bluetooth_spi_process);
-        etimer_set(&observe_restart_timer, OBSERVE_RESTART_INTERVAL);
-        PROCESS_CONTEXT_END(&pbdrv_bluetooth_spi_process);
-        observe_restart_enabled = true;
+        observe_restart_time = pbdrv_clock_get_ms();
+        observe_restart_requested = false;
     }
 
     task->status = PBIO_SUCCESS;
@@ -1201,11 +1196,16 @@ static PT_THREAD(stop_observe_task(struct pt *pt, pbio_task_t *task)) {
 void pbdrv_bluetooth_stop_observing(pbio_task_t *task) {
     observe_callback = NULL;
     // avoid restarting observing even if this task get queued
-    observe_restart_enabled = false;
+    observe_restart_requested = false;
 
     start_task(task, stop_observe_task, NULL);
 }
 
+void pbdrv_bluetooth_restart_observing_request(void) {
+    observe_restart_requested = true;
+    process_poll(&pbdrv_bluetooth_spi_process);
+}
+
 // Driver interrupt callbacks
 
 void pbdrv_bluetooth_stm32_cc2640_srdy_irq(bool srdy) {
@@ -2250,7 +2250,7 @@ PROCESS_THREAD(pbdrv_bluetooth_spi_process, ev, data) {
         spi_set_mrdy(false);
         bluetooth_reset(RESET_STATE_OUT_LOW);
         bluetooth_ready = pybricks_notify_en = uart_tx_notify_en =
-            is_broadcasting = is_observing = observe_restart_enabled = false;
+            is_broadcasting = is_observing = observe_restart_requested = false;
         conn_handle = peripheral_singleton.con_handle = NO_CONNECTION;
 
         pbio_task_t *task;
@@ -2309,11 +2309,14 @@ PROCESS_THREAD(pbdrv_bluetooth_spi_process, ev, data) {
     for (;;) {
         PROCESS_WAIT_UNTIL({
             for (;;) {
-                if (observe_restart_enabled && etimer_expired(&observe_restart_timer)) {
+                if (observe_restart_requested && pbdrv_clock_get_ms() - observe_restart_time > OBSERVE_RESTART_INTERVAL) {
                     static pbio_task_t observe_restart_stop_task;
                     static pbio_task_t observe_restart_start_task;
                     pbdrv_bluetooth_start_observing_callback_t callback = observe_callback;
 
+                    // Avoid queueing this more than once.
+                    observe_restart_time = pbdrv_clock_get_ms();
+
                     pbdrv_bluetooth_stop_observing(&observe_restart_stop_task);
                     pbdrv_bluetooth_start_observing(&observe_restart_start_task, callback);
                 }

pybricks/common/pb_type_ble.c

@@ -440,6 +440,12 @@ static mp_obj_t pb_module_ble_observe(mp_obj_t self_in, mp_obj_t channel_in) {
 
     // Have not received data yet or timed out.
     if (ch_data.rssi == INT8_MIN) {
+
+        #if PBDRV_CONFIG_BLUETOOTH_STM32_CC2640
+        extern void pbdrv_bluetooth_restart_observing_request(void);
+        pbdrv_bluetooth_restart_observing_request();
+        #endif
+
         return mp_const_none;
     }