sound getInstance and release mutex correctly

src/sound.cpp

@@ -32,9 +32,15 @@ using namespace std;
 
 SemaphoreHandle_t xPlayingSemaphore = NULL;
 static TaskHandle_t xTaskToNotify = NULL;
+Sound* Sound::instance = NULL;
 
 Sound::Sound() {
     xPlayingSemaphore = xSemaphoreCreateMutex();
+    Sound::instance = this;
+}
+
+Sound* Sound::getInstance() {
+    return Sound::instance;
 }
 
 void Sound::init() {
@@ -117,8 +123,9 @@ void Sound::play_task(void *pvParameter) {
 
   File file = SDCard::open(path); // ToDo: accessing static member function loads 1500 words onto stack!
   if (!file) {
-    xTaskToNotify = NULL;
     Serial.print("Failed to open file: "); Serial.println(path);
+    xTaskToNotify = NULL;
+    xSemaphoreGive( xPlayingSemaphore );
     vTaskDelete( NULL );
     return;
   }

src/sound.h

@@ -18,8 +18,10 @@ class Sound {
 //    void stop();
     static const i2s_port_t i2s_num = (i2s_port_t)I2S_NUM;
     static void play_task(void *pvParameter);
+    static Sound* getInstance();
   private:
     TaskHandle_t xTaskSound = NULL;
+    static Sound* instance;
 };
 
 #endif /* _SOUND_H */