Minor corrections for the XMEGA USB controller. Add compile time warning if the USB clock frequency is provably incorrect.

LUFA/Drivers/USB/Core/XMEGA/Endpoint_XMEGA.h

@@ -291,6 +291,10 @@
 			{
 				uint8_t EPConfigMask = (USB_EP_INTDSBL_bm | Banks | Endpoint_BytesToEPSizeMask(Size));
 				
+				// TODO - Fix once limitations are lifted
+				if ((Banks != ENDPOINT_BANK_SINGLE) || (Size > 64))
+				  return false;
+
 				switch (Type)
 				{
 					case EP_TYPE_CONTROL:
@@ -489,8 +493,8 @@
 			static inline void Endpoint_ClearSETUP(void) ATTR_ALWAYS_INLINE;
 			static inline void Endpoint_ClearSETUP(void)
 			{
+				Endpoint_SelectEndpoint(USB_Endpoint_SelectedEndpoint & ~ENDPOINT_DIR_IN);
 				USB_Endpoint_SelectedHandle->STATUS &= ~(USB_EP_SETUP_bm | USB_EP_TRNCOMPL0_bm | USB_EP_BUSNACK0_bm | USB_EP_OVF_bm);
-
 				USB_Endpoint_SelectedHandle->STATUS |= USB_EP_TOGGLE_bm;
 				USB_Endpoint_SelectedFIFO->Position  = 0;
 
@@ -543,7 +547,7 @@
 				if ((USB_Endpoint_SelectedHandle->CTRL & USB_EP_TYPE_gm) == USB_EP_TYPE_CONTROL_gc)
 				{
 					Endpoint_SelectEndpoint(USB_Endpoint_SelectedEndpoint |  ENDPOINT_DIR_IN);
-					USB_Endpoint_SelectedHandle->STATUS |= USB_EP_STALL_bm;
+					USB_Endpoint_SelectedHandle->CTRL |= USB_EP_STALL_bm;
 					Endpoint_SelectEndpoint(USB_Endpoint_SelectedEndpoint & ~ENDPOINT_DIR_IN);
 				}
 			}
@@ -567,7 +571,7 @@
 			static inline bool Endpoint_IsStalled(void) ATTR_WARN_UNUSED_RESULT ATTR_ALWAYS_INLINE;
 			static inline bool Endpoint_IsStalled(void)
 			{
-				return ((USB_Endpoint_SelectedHandle->STATUS & USB_EP_STALLF_bm) ? true : false);
+				return ((USB_Endpoint_SelectedHandle->CTRL & USB_EP_STALL_bm) ? true : false);
 			}
 
 			/** Resets the data toggle of the currently selected endpoint. */

LUFA/Drivers/USB/Core/XMEGA/USBController_XMEGA.h

@@ -95,6 +95,10 @@
 			#error F_USB is not defined. You must define F_USB to the frequency of the unprescaled USB controller clock in your project makefile.
 		#endif
 		
+		#if (F_USB % 6000000)
+			#error Invalid F_USB specified. F_USB must be a multiple of 6MHz for USB Low Speed operation, and a multiple of 48MHz for Full Speed operation.
+		#endif
+
 	/* Public Interface - May be used in end-application: */
 		/* Macros: */
 			/** \name USB Controller Option Masks */