pbio/sys/core: Monitor disconnection change.

This is a basic test to unset the connection status to clear the Bluetooth light.

This is expected to be generalized when we complete USB support with a proper status indicator. For now, this suffices to avoid introducing a regression after the recent Bluetooth overhaul.

Fixes: pybricks/support#2355

Author: laurensvalk

lib/pbio/sys/core.c

@@ -3,6 +3,7 @@
 
 #include <stdint.h>
 
+#include <pbdrv/bluetooth.h>
 #include <pbdrv/watchdog.h>
 
 #include <pbio/busy_count.h>
@@ -37,6 +38,11 @@ PROCESS_THREAD(pbsys_system_process, ev, data) {
             pbsys_program_stop_poll();
             pbsys_status_light_poll();
 
+            // Revisit: Use pbio/sys/host callback to indicate connection changes.
+            if (!pbdrv_bluetooth_is_connected(PBDRV_BLUETOOTH_CONNECTION_LE)) {
+                pbsys_status_clear(PBIO_PYBRICKS_STATUS_BLE_HOST_CONNECTED);
+            }
+
             // keep the hub from resetting itself
             pbdrv_watchdog_update();
         }