move yield() to main.cpp

cores/arduino/TinyUSB/Adafruit_TinyUSB_Core.cpp

@@ -100,19 +100,6 @@ uint8_t Adafruit_USBD_Device::getSerialDescriptor(uint16_t* serial_str)
   return sizeof(raw_id)*2;
 }
 
-
-extern  "C"
-{
-
-// running tinyusb background task if yield()
-void yield(void)
-{
-  tud_task();
-  tud_cdc_write_flush();
-}
-
-}
-
 //--------------------------------------------------------------------+
 // Helpers
 //--------------------------------------------------------------------+

cores/arduino/main.cpp

@@ -59,3 +59,14 @@ int main( void )
 
   return 0;
 }
+
+#if defined(USE_TINYUSB)
+
+// run TinyUSB background task when yield()
+extern  "C" void yield(void)
+{
+  tud_task();
+  tud_cdc_write_flush();
+}
+
+#endif