make sound work

lib/FatFs_SPI/include/rtc.h

@@ -0,0 +1,24 @@
+/* rtc.h
+Copyright 2021 Carl John Kugler III
+
+Licensed under the Apache License, Version 2.0 (the License); you may not use 
+this file except in compliance with the License. You may obtain a copy of the 
+License at
+
+   http://www.apache.org/licenses/LICENSE-2.0 
+Unless required by applicable law or agreed to in writing, software distributed 
+under the License is distributed on an AS IS BASIS, WITHOUT WARRANTIES OR 
+CONDITIONS OF ANY KIND, either express or implied. See the License for the 
+specific language governing permissions and limitations under the License.
+*/
+#pragma once
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+void time_init();
+
+#ifdef __cplusplus
+}
+#endif