microbit: BUGFIX Corrected incorrect handling of MicroBitMessageBus::add return values.

inc/MicroBitMessageBus.h

@@ -256,7 +256,7 @@ class MicroBitMessageBus : public MicroBitComponent
 };
 
 /**
-  * A registrationt function to allow C++ member funcitons (methods) to be registered as an event
+  * A registration function to allow C++ member funcitons (methods) to be registered as an event
   * listener.
   *
   * @param id The source of messages to listen for. Events sent from any other IDs will be filtered. 
@@ -278,10 +278,11 @@ int MicroBitMessageBus::listen(uint16_t id, uint16_t value, T* object, void (T::
 
 	MicroBitListener *newListener = new MicroBitListener(id, value, object, handler, flags);
 
-    if(!add(newListener))
-        delete newListener;
+    if(add(newListener) == MICROBIT_OK)
+        return MICROBIT_OK;
 
-    return MICROBIT_OK;
+    delete newListener;
+    return MICROBIT_NO_RESOURCES;
 }
 
 /**

source/MicroBitMessageBus.cpp

@@ -288,10 +288,12 @@ int MicroBitMessageBus::listen(int id, int value, void (*handler)(MicroBitEvent)
 
 	MicroBitListener *newListener = new MicroBitListener(id, value, handler, flags);
 
-    if(add(newListener) != MICROBIT_OK)
-        delete newListener;
+    if(add(newListener) == MICROBIT_OK)
+        return MICROBIT_OK;
+
+    delete newListener;
+    return MICROBIT_NO_RESOURCES;
 
-    return MICROBIT_OK;
 }
 
 int MicroBitMessageBus::listen(int id, int value, void (*handler)(MicroBitEvent, void*), void* arg, uint16_t flags) 
@@ -301,10 +303,11 @@ int MicroBitMessageBus::listen(int id, int value, void (*handler)(MicroBitEvent,
 
 	MicroBitListener *newListener = new MicroBitListener(id, value, handler, arg, flags);
 
-    if(add(newListener) != MICROBIT_OK)
-        delete newListener;
-
+    if(add(newListener) == MICROBIT_OK)
     return MICROBIT_OK;
+
+    delete newListener;
+    return MICROBIT_NO_RESOURCES;
 }
 
 /**

source/ble-services/MicroBitMagnetometerService.cpp

@@ -48,8 +48,7 @@ MicroBitMagnetometerService::MicroBitMagnetometerService(BLEDevice &_ble) :
     ble.gattServer().write(magnetometerPeriodCharacteristicHandle, (const uint8_t *)&magnetometerPeriodCharacteristicBuffer, sizeof(magnetometerPeriodCharacteristicBuffer));
 
     ble.onDataWritten(this, &MicroBitMagnetometerService::onDataWritten);
-    uBit.MessageBus.listen(MICROBIT_ID_COMPASS, MICROBIT_COMPASS_EVT_DATA_UPDATE, this, &MicroBitMagnetometerService::magnetometerUpdate);
-
+    uBit.MessageBus.listen(MICROBIT_ID_COMPASS, MICROBIT_COMPASS_EVT_DATA_UPDATE, this, &MicroBitMagnetometerService::magnetometerUpdate, MESSAGE_BUS_LISTENER_IMMEDIATE);
     uBit.MessageBus.listen(MICROBIT_ID_COMPASS, MICROBIT_COMPASS_EVT_CONFIG_NEEDED, this, &MicroBitMagnetometerService::samplePeriodUpdateNeeded);
 }