The compass app now updates it's azimuth and temperature by itself with a timer and doesn't rely on the main loop to do so. It also, through a callback, put the magnetometer in active or standby mode to save power when leaving the app

src/W800_SDK_v1.00.10/app/gfx/compass_screen.c

@@ -20,7 +20,6 @@ static const char *cardinals[] =
 static void gesture_event_cb(lv_event_t * e)
 {
     CompassScreen_t *compassScreen = e->user_data;
-    (void)compassScreen;
 
     lv_dir_t gesture;
     switch(gesture = lv_indev_get_gesture_dir(lv_indev_get_act()))
@@ -30,6 +29,8 @@ static void gesture_event_cb(lv_event_t * e)
         break;
     case LV_DIR_RIGHT:
         LV_LOG_USER("GESTURE : RIGHT");
+        // We delete the refresh timer
+        lv_timer_del(compassScreen->refreshTimer);
         // We create the menu screen and switch to it
         extern MenuScreen_t menuScreen;
         menu_screen_create(&menuScreen);
@@ -53,6 +54,23 @@ static void cleanup_event_cb(lv_event_t * e)
     LV_LOG_USER("cleanup");
 }
 
+static void _compass_screen_refresh_timer_cb(lv_timer_t *timer)
+{
+    CompassScreen_t *compassScreen = timer->user_data;
+
+    if(compassScreen->compassScreenAzimuthAndTemperatureCb)
+    {
+        uint16_t azimuth = 0;
+        float temperature = 0.0f;
+        bool refreshAzimuth = true, refreshTemperature = true;
+
+        compassScreen->compassScreenAzimuthAndTemperatureCb(&azimuth, &refreshAzimuth, &temperature, &refreshTemperature);
+
+        if(refreshAzimuth)compass_screen_set_azimuth(compassScreen, azimuth);
+        if(refreshTemperature)compass_screen_set_temperature(compassScreen, temperature);
+    }
+}
+
 static void create_cardinal(CompassCardinal_t *cardidanl, const char *cardinalText, lv_color_t textColor, lv_coord_t x, lv_coord_t y, lv_obj_t *parent)
 {
     cardidanl->label = lv_label_create(parent);
@@ -93,6 +111,29 @@ void compass_screen_init(CompassScreen_t * const compassScreen)
 
     memset(compassScreen, 0, sizeof(CompassScreen_t));
     strcpy(compassScreen->compassAzimuth.text, "0° N");
+    strcpy(compassScreen->compassTemperature.text, "0.00°C");
+}
+
+void compass_screen_register_on_state_change_cb(CompassScreen_t * const compassScreen, CompassScreenOnStateChangeCb_t compassScreenOnStateChangeCb)
+{
+    if(!compassScreen)
+    {
+        LV_LOG_ERROR("NULL pointer given !");
+        return;
+    }
+
+    compassScreen->compassScreenOnStateChangeCb = compassScreenOnStateChangeCb;
+}
+
+void compass_screen_register_azimuth_and_temperature_cb(CompassScreen_t * const compassScreen, CompassScreenAzimuthAndTemperatureCb_t compassScreenAzimuthAndTemperatureCb)
+{
+    if(!compassScreen)
+    {
+        LV_LOG_ERROR("NULL pointer given !");
+        return;
+    }
+
+    compassScreen->compassScreenAzimuthAndTemperatureCb = compassScreenAzimuthAndTemperatureCb;
 }
 
 void compass_screen_set_azimuth(CompassScreen_t * const compassScreen, uint16_t azimuth)
@@ -317,6 +358,18 @@ void compass_screen_create(CompassScreen_t * const compassScreen)
     lv_obj_add_event_cb(compassScreen->display, &(gesture_event_cb), LV_EVENT_GESTURE, compassScreen);
     //We register the event callback to handle the cleanup
     lv_obj_add_event_cb(compassScreen->display, &(cleanup_event_cb), LV_EVENT_DELETE, compassScreen);
+
+    //We create the refresh timer
+    if(compassScreen->refreshTimer)
+    {
+        LV_LOG_ERROR("refreshTimer should be NULL here !");
+        lv_timer_del(compassScreen->refreshTimer);
+        compassScreen->refreshTimer = NULL;
+    }
+
+    if(compassScreen->compassScreenOnStateChangeCb) compassScreen->compassScreenOnStateChangeCb(COMPASS_SCREEN_STATE_OPENED);
+
+    compassScreen->refreshTimer = lv_timer_create(&(_compass_screen_refresh_timer_cb), 20, compassScreen);
 }
 
 void compass_screen_destroy(CompassScreen_t * const compassScreen)
@@ -337,4 +390,7 @@ void compass_screen_destroy(CompassScreen_t * const compassScreen)
     compassScreen->northMarker              = NULL;
     //compassScreen->compassGraduation.meter  = NULL;
     //compassScreen->compassGraduation.scale  = NULL;
+    compassScreen->refreshTimer             = NULL;
+
+    if(compassScreen->compassScreenOnStateChangeCb) compassScreen->compassScreenOnStateChangeCb(COMPASS_SCREEN_STATE_CLOSED);
 }

src/W800_SDK_v1.00.10/app/gfx/compass_screen.h

@@ -22,6 +22,15 @@ typedef struct CompassCardinal
     lv_meter_scale_t *scale;
 } CompassGraduation_t;*/
 
+typedef enum CompassScreenState
+{
+    COMPASS_SCREEN_STATE_OPENED = 0,
+    COMPASS_SCREEN_STATE_CLOSED
+} CompassScreenState_e;
+
+typedef void (*CompassScreenOnStateChangeCb_t)(CompassScreenState_e compassScreenState);
+typedef void (*CompassScreenAzimuthAndTemperatureCb_t)(uint16_t *azimuth, bool *refreshAzimuth, float *temperature, bool *refreshTemperature);
+
 /* Compass screen context object */
 typedef struct CompassScreen
 {
@@ -37,6 +46,11 @@ typedef struct CompassScreen
 
     CompassLabel_t compassAzimuth;
     CompassLabel_t compassTemperature;
+
+    CompassScreenOnStateChangeCb_t compassScreenOnStateChangeCb;
+    CompassScreenAzimuthAndTemperatureCb_t compassScreenAzimuthAndTemperatureCb;
+
+    lv_timer_t *refreshTimer;
 } CompassScreen_t;
 
 /**
@@ -47,6 +61,26 @@ typedef struct CompassScreen
  */
 void compass_screen_init(CompassScreen_t * const compassScreen);
 
+/**
+ * @brief Registers a callback function which will be called every time the state of the application changes ie : is opened or closed.
+ *        This callback should be used to initialize and deinitialize needed devices drivers like the magnetometer or the temperature sensor.
+ * @note The state of the application is passed as a parameter or the callback function. 
+ * 
+ * @param compassScreen a pointer to the compass screen object structure.
+ * @param compassScreenOnStateChangeCb the callback of type @ref CompassScreenOnStateChangeCb_t to register.
+ */
+void compass_screen_register_on_state_change_cb(CompassScreen_t * const compassScreen, CompassScreenOnStateChangeCb_t compassScreenOnStateChangeCb);
+
+/**
+ * @brief Registers a callback function which will be executed every time the compass refreshes.
+ *        This callback should retrieve the azimuth and temperature and pass it through the provided pointers.
+ * @note If no new magnetometer or temperature data is available upon the function call, set the associated refresh parameter to false;
+ * 
+ * @param compassScreen a pointer to the compass screen object structure.
+ * @param compassScreenOnStateChangeCb the callback of type CompassScreenAzimuthAndTemperatureCb_t to register.
+ */
+void compass_screen_register_azimuth_and_temperature_cb(CompassScreen_t * const compassScreen, CompassScreenAzimuthAndTemperatureCb_t compassScreenAzimuthAndTemperatureCb);
+
 /**
  * @brief Sets the azimuth in degrees (relative to the north) to show on the compass UI.
  * 

src/lvgl_win_sim/lv_port_win_codeblocks/compass_screen.c

@@ -28,6 +28,8 @@ static void gesture_event_cb(lv_event_t * e)
         break;
     case LV_DIR_RIGHT:
         LV_LOG_USER("GESTURE : RIGHT");
+        // We delete the refresh timer
+        lv_timer_del(compassScreen->refreshTimer);
         // We create the menu screen and switch to it
         extern MenuScreen_t menuScreen;
         menu_screen_create(&menuScreen);
@@ -44,8 +46,6 @@ static void gesture_event_cb(lv_event_t * e)
     }
 }
 
-static lv_timer_t *timer;
-
 static void cleanup_event_cb(lv_event_t * e)
 {
     CompassScreen_t *compassScreen = e->user_data;
@@ -53,18 +53,20 @@ static void cleanup_event_cb(lv_event_t * e)
     LV_LOG_USER("cleanup");
 }
 
-//To delete
+static void _compass_screen_refresh_timer_cb(lv_timer_t *timer)
-static void timer_anim_cb(lv_timer_t *timer)
 {
     CompassScreen_t *compassScreen = timer->user_data;
-    static uint16_t azimuth = 0;
-    static float temp = -20;
-    compass_screen_set_azimuth(compassScreen, azimuth++);
-    compass_screen_set_temperature(compassScreen, temp+=0.09);
 
-    if(temp > 120) temp = -20;
+    if(compassScreen->compassScreenAzimuthAndTemperatureCb)
+    {
+        uint16_t azimuth = 0;
+        float temperature = 0.0f;
 
-    //lv_meter_set_scale_range(compassScreen->compassGraduation.meter, compassScreen->compassGraduation.scale, 0, 330, 330, -azimuth-90);
+        compassScreen->compassScreenAzimuthAndTemperatureCb(&azimuth, &temperature);
+
+        compass_screen_set_azimuth(compassScreen, azimuth);
+        compass_screen_set_temperature(compassScreen, temperature);
+    }
 }
 
 static void create_cardinal(CompassCardinal_t *cardidanl, const char *cardinalText, lv_color_t textColor, lv_coord_t x, lv_coord_t y, lv_obj_t *parent)
@@ -106,6 +108,28 @@ void compass_screen_init(CompassScreen_t * const compassScreen)
     strcpy(compassScreen->compassTemperature.text, "0.00°C");
 }
 
+void compass_screen_register_on_state_change_cb(CompassScreen_t * const compassScreen, CompassScreenOnStateChangeCb_t compassScreenOnStateChangeCb)
+{
+    if(!compassScreen)
+    {
+        LV_LOG_ERROR("NULL pointer given !");
+        return;
+    }
+
+    compassScreen->compassScreenOnStateChangeCb = compassScreenOnStateChangeCb;
+}
+
+void compass_screen_register_azimuth_and_temperature_cb(CompassScreen_t * const compassScreen, CompassScreenAzimuthAndTemperatureCb_t compassScreenAzimuthAndTemperatureCb)
+{
+    if(!compassScreen)
+    {
+        LV_LOG_ERROR("NULL pointer given !");
+        return;
+    }
+
+    compassScreen->compassScreenAzimuthAndTemperatureCb = compassScreenAzimuthAndTemperatureCb;
+}
+
 void compass_screen_set_azimuth(CompassScreen_t * const compassScreen, uint16_t azimuth)
 {
     if(!compassScreen)
@@ -165,7 +189,17 @@ void compass_screen_set_temperature(CompassScreen_t * const compassScreen, float
     //Update the temperature label
     sprintf(compassScreen->compassTemperature.text, "%.2f°C", temperature);
     lv_label_set_text_static(compassScreen->compassTemperature.label, compassScreen->compassTemperature.text);
+}
 
+bool compass_screen_is_in_use(CompassScreen_t *const compassScreen)
+{
+    if(!compassScreen)
+    {
+        LV_LOG_ERROR("NULL pointer given !");
+        return false;
+    }
+
+    return compassScreen->display != NULL;
 }
 
 void compass_screen_create(CompassScreen_t * const compassScreen)
@@ -191,7 +225,7 @@ void compass_screen_create(CompassScreen_t * const compassScreen)
     compassScreen->display = lv_obj_create(NULL);
     lv_obj_set_style_bg_color(compassScreen->display, lv_color_white(), LV_PART_MAIN);
 
-    //Let's try to add some arcs
+    //Let's add some arcs
     lv_obj_t *arc = lv_arc_create(compassScreen->display);
     lv_arc_set_angles(arc, 0, 360);
     lv_obj_set_style_arc_width(arc, 2, LV_PART_INDICATOR);
@@ -308,8 +342,17 @@ void compass_screen_create(CompassScreen_t * const compassScreen)
     //We register the event callback to handle the cleanup
     lv_obj_add_event_cb(compassScreen->display, &(cleanup_event_cb), LV_EVENT_DELETE, compassScreen);
 
-    //To delete
+    //We create the refresh timer
-    timer = lv_timer_create(&(timer_anim_cb), 2, compassScreen);
+    if(compassScreen->refreshTimer)
+    {
+        LV_LOG_ERROR("refreshTimer should be NULL here !");
+        lv_timer_del(compassScreen->refreshTimer);
+        compassScreen->refreshTimer = NULL;
+    }
+
+    if(compassScreen->compassScreenOnStateChangeCb) compassScreen->compassScreenOnStateChangeCb(COMPASS_SCREEN_OPENED);
+
+    compassScreen->refreshTimer = lv_timer_create(&(_compass_screen_refresh_timer_cb), 20, compassScreen);
 }
 
 void compass_screen_destroy(CompassScreen_t * const compassScreen)
@@ -330,6 +373,7 @@ void compass_screen_destroy(CompassScreen_t * const compassScreen)
     compassScreen->northMarker              = NULL;
     compassScreen->compassGraduation.meter  = NULL;
     compassScreen->compassGraduation.scale  = NULL;
+    compassScreen->refreshTimer             = NULL;
 
-    lv_timer_del(timer);
+    if(compassScreen->compassScreenOnStateChangeCb) compassScreen->compassScreenOnStateChangeCb(COMPASS_SCREEN_CLOSED);
 }

src/lvgl_win_sim/lv_port_win_codeblocks/compass_screen.h

@@ -22,6 +22,16 @@ typedef struct CompassGraduation
     lv_meter_scale_t *scale;
 } CompassGraduation_t;
 
+typedef enum CompassScreenState
+{
+    COMPASS_SCREEN_OPENED = 0,
+    COMPASS_SCREEN_CLOSED
+} CompassScreenState_e;
+
+typedef void (*CompassScreenOnStateChangeCb_t)(CompassScreenState_e compassScreenState);
+
+typedef void (*CompassScreenAzimuthAndTemperatureCb_t)(uint16_t *azimuth, float *temperature);
+
 /* Compass screen context object */
 typedef struct CompassScreen
 {
@@ -37,21 +47,77 @@ typedef struct CompassScreen
 
     CompassLabel_t compassAzimuth;
     CompassLabel_t compassTemperature;
+
+    CompassScreenOnStateChangeCb_t compassScreenOnStateChangeCb;
+    CompassScreenAzimuthAndTemperatureCb_t compassScreenAzimuthAndTemperatureCb;
+
+    lv_timer_t *refreshTimer;
 } CompassScreen_t;
 
-/* Initializes the compass screen context object */
+/**
+ * @brief Initializes the compass screen object structure.
+ * @note This function has to be called first before any others.
+ * 
+ * @param compassScreen a pointer to the compass screen object structure to initialize. 
+ */
 void compass_screen_init(CompassScreen_t * const compassScreen);
 
-/* Set the compassAzimuth in degrees to show */
+/**
+ * @brief Registers a callback function which will be called every time the state of the application changes ie : is opened or closed.
+ *        This callback should be used to initialize and deinitialize needed devices drivers like the magnetometer or the temperature sensor.
+ * @note The state of the application is passed as a parameter or the callback function. 
+ * 
+ * @param compassScreen a pointer to the compass screen object structure.
+ * @param compassScreenOnStateChangeCb the callback of type CompassScreenOnStateChangeCb_t to register.
+ */
+void compass_screen_register_on_state_change_cb(CompassScreen_t * const compassScreen, CompassScreenOnStateChangeCb_t compassScreenOnStateChangeCb);
+
+/**
+ * @brief Registers a callback function which will be executed every time the compass refreshes.
+ *        This callback should retrieve the azimuth and temperature and pass it through the provided pointers.
+ * 
+ * @param compassScreen a pointer to the compass screen object structure.
+ * @param compassScreenOnStateChangeCb the callback of type CompassScreenAzimuthAndTemperatureCb_t to register.
+ */
+void compass_screen_register_azimuth_and_temperature_cb(CompassScreen_t * const compassScreen, CompassScreenAzimuthAndTemperatureCb_t compassScreenAzimuthAndTemperatureCb);
+
+/**
+ * @brief Sets the azimuth in degrees (relative to the north) to show on the compass UI.
+ * 
+ * @param compassScreen a pointer to the compass screen object structure. 
+ * @param azimuth the azimuth in degrees (0 to 359) relative to north to show. 
+ */
 void compass_screen_set_azimuth(CompassScreen_t * const compassScreen, uint16_t azimuth);
 
-/* Set the compassTemperature in degrees celsius to show */
+/**
+ * @brief Sets the temperature in degrees celsius to show on the compass UI.
+ * 
+ * @param compassScreen a pointer to the compass screen object structure. 
+ * @param temperature the temperature to display on the compass screen in degrees celsius.
+ */
 void compass_screen_set_temperature(CompassScreen_t * const compassScreen, float temperature);
 
-/* Builds the compass screen graphically  */
+/**
+ * @brief Returns true if the compass screen is currently being used and displayed.
+ * 
+ * @param compassScreen a pointer to the compass screen object structure. 
+ * @return true if the compass screen is being used .
+ * @return false if the compass screen is not being used/currently displayed.
+ */
+bool compass_screen_is_in_use(CompassScreen_t * const compassScreen);
+
+/**
+ * @brief Builds the compass screen graphically.
+ * 
+ * @param compassScreen a pointer to the compass screen object structure.
+ */
 void compass_screen_create(CompassScreen_t * const compassScreen);
 
-/* Frees all resources used by the CompassScreen object */
+/**
+ * @brief Frees all resources used by the CompassScreen object, to be called when discarding the compass screen.
+ * 
+ * @param compassScreen a pointer to the compass screen object structure.
+ */
 void compass_screen_destroy(CompassScreen_t * const compassScreen);
 
 #endif // COMPASS_SCREEN_H