diff --git a/sam3s_example/simtrace/usb.c b/sam3s_example/simtrace/usb.c
index 8edaf557..1e200620 100644
--- a/sam3s_example/simtrace/usb.c
+++ b/sam3s_example/simtrace/usb.c
@@ -428,6 +428,21 @@ const USBDDriverDescriptors driverDescriptors = {
     STRING_DESC_CNT /* cnt string descriptors in list */
 };
 
+
+/*----------------------------------------------------------------------------
+ *       Callbacks
+ *----------------------------------------------------------------------------*/
+extern uint8_t conf_changed;
+extern uint8_t simtrace_config;
+
+void USBDDriverCallbacks_ConfigurationChanged(uint8_t cfgnum)
+{
+    TRACE_INFO_WP("cfgChanged%d ", cfgnum);
+    conf_changed =1;
+    simtrace_config = cfgnum;
+}
+
+
 /*----------------------------------------------------------------------------
  *        Functions 
  *----------------------------------------------------------------------------*/