diff --git a/sam3s_example/Makefile b/sam3s_example/Makefile
index 042c871..ba686cd 100644
--- a/sam3s_example/Makefile
+++ b/sam3s_example/Makefile
@@ -97,21 +97,24 @@
 INCLUDES += $(INCLUDES_USB)
 #INCLUDES += -I$(LIBRARIES)
 
-CFLAGS += -Wall -Wchar-subscripts -Wcomment -Wimplicit-int #-Wformat=2 
+CFLAGS += -Wall -Wchar-subscripts -Wcomment -Wimplicit-int -Wformat=2 
 CFLAGS += -Werror-implicit-function-declaration -Wmain -Wparentheses
 CFLAGS += -Wsequence-point -Wreturn-type -Wswitch -Wtrigraphs #-Wunused
 CFLAGS += -Wuninitialized -Wunknown-pragmas -Wfloat-equal -Wundef
 CFLAGS += -Wshadow -Wpointer-arith -Wbad-function-cast -Wwrite-strings
 CFLAGS += -Wsign-compare -Waggregate-return
-#CFLAGS += -Wformat 
+CFLAGS += -Wformat 
 CFLAGS += -Wmissing-format-attribute -Wno-deprecated-declarations
-#CFLAGS += -Wpacked 
+CFLAGS += #-Wpacked 
 CFLAGS += -Wredundant-decls -Wnested-externs -Winline #-Wlong-long
 CFLAGS += -Wunreachable-code
 CFLAGS += -Wcast-align
 CFLAGS += -std=c11
-#CFLAGS += -Wmissing-noreturn
+CFLAGS += -Wmissing-noreturn
 #CFLAGS += -Wconversion
+# Disable unused variable warnings
+CFLAGS += -Wno-unused-but-set-variable -Wno-unused-variable
+CFLAGS += -Wno-suggest-attribute=noreturn
 
 # To reduce application size use only integer printf function.
 #CFLAGS += -Dprintf=iprintf
@@ -166,7 +169,7 @@
 
 $$(C_OBJECTS_$(1)): $(OBJ)/$(1)_%.o: %.c Makefile $(OBJ) $(BIN)
 	@echo [COMPILING $$@]
-	@$(CC) $(CFLAGS) -D$(1) -Wa,-ahlms=$(BIN)/$$*.lst -c -o $$@ $$<  
+	$(CC) $(CFLAGS) -D$(1) -Wa,-ahlms=$(BIN)/$$*.lst -c -o $$@ $$<  
 
 $$(ASM_OBJECTS_$(1)): $(OBJ)/$(1)_%.o: %.S Makefile $(OBJ) $(BIN)
 	@echo [ASSEMBLING $$@]
diff --git a/sam3s_example/atmel_softpack_libraries/libboard_sam3s-ek/source/iso7816_4.c b/sam3s_example/atmel_softpack_libraries/libboard_sam3s-ek/source/iso7816_4.c
index bbb831c..5ee78c2 100644
--- a/sam3s_example/atmel_softpack_libraries/libboard_sam3s-ek/source/iso7816_4.c
+++ b/sam3s_example/atmel_softpack_libraries/libboard_sam3s-ek/source/iso7816_4.c
@@ -108,9 +108,9 @@
                                       (1<<10)));
 
     if (status != 0 ) {
-        TRACE_DEBUG("R:0x%X\n\r", status); 
-        TRACE_DEBUG("R:0x%X\n\r", BOARD_ISO7816_BASE_USART->US_CSR);
-        TRACE_DEBUG("Nb:0x%X\n\r", BOARD_ISO7816_BASE_USART->US_NER );
+        TRACE_DEBUG("R:0x%" PRIX32 "\n\r", status); 
+        TRACE_DEBUG("R:0x%" PRIX32 "\n\r", BOARD_ISO7816_BASE_USART->US_CSR);
+        TRACE_DEBUG("Nb:0x%" PRIX32 "\n\r", BOARD_ISO7816_BASE_USART->US_NER );
         BOARD_ISO7816_BASE_USART->US_CR = US_CR_RSTSTA;
     }
 
@@ -147,12 +147,12 @@
                                       (1<<10)));
 
     if (status != 0 ) {
-        TRACE_DEBUG("******* status: 0x%X (Overrun: %d, NACK: %d, Timeout: %d, underrun: %d)\n\r", 
+        TRACE_DEBUG("******* status: 0x%" PRIX32 " (Overrun: %" PRIX32 ", NACK: %" PRIX32 ", Timeout: %" PRIX32 ", underrun: %" PRIX32 ")\n\r", 
                     status, ((status & US_CSR_OVRE)>> 5), ((status & US_CSR_NACK) >> 13), 
                     ((status & US_CSR_TIMEOUT) >> 8), ((status & (1 << 10)) >> 10));
         
-        TRACE_DEBUG("E (USART CSR reg):0x%X\n\r", BOARD_ISO7816_BASE_USART->US_CSR);
-        TRACE_DEBUG("Nb (Number of errors):0x%X\n\r", BOARD_ISO7816_BASE_USART->US_NER );
+        TRACE_DEBUG("E (USART CSR reg):0x%" PRIX32 "\n\r", BOARD_ISO7816_BASE_USART->US_CSR);
+        TRACE_DEBUG("Nb (Number of errors):0x%" PRIX32 "\n\r", BOARD_ISO7816_BASE_USART->US_NER );
         BOARD_ISO7816_BASE_USART->US_CR = US_CR_RSTSTA;
     }
 
diff --git a/sam3s_example/atmel_softpack_libraries/libchip_sam3s/source/USBD_HAL.c b/sam3s_example/atmel_softpack_libraries/libchip_sam3s/source/USBD_HAL.c
index 6930a5e..d5ec38e 100644
--- a/sam3s_example/atmel_softpack_libraries/libchip_sam3s/source/USBD_HAL.c
+++ b/sam3s_example/atmel_softpack_libraries/libchip_sam3s/source/USBD_HAL.c
@@ -508,7 +508,7 @@
     size = pEndpoint->size;
     if (size > pBi->remaining) size = pBi->remaining;
 
-    TRACE_DEBUG_WP("w%d.%d ", pTransfer->outCurr, size);
+    TRACE_DEBUG_WP("w%d.%" PRId32 " ", pTransfer->outCurr, size);
 
     /* Record last accessed buffer */
     pTransfer->outLast = pTransfer->outCurr;
@@ -659,7 +659,7 @@
     USBGenericRequest request;
 
     TRACE_DEBUG_WP("E%d ", bEndpoint);
-    TRACE_DEBUG_WP("st:0x%X ", status);
+    TRACE_DEBUG_WP("st:0x%" PRIX32 " ", status);
 
     // Handle interrupts
     // IN packet sent
@@ -908,7 +908,7 @@
 
         return USBD_STATUS_LOCKED;
     }
-    TRACE_DEBUG_WP("Write%d(%d) ", bEndpoint, dLength);
+    TRACE_DEBUG_WP("Write%d(%" PRIu32 ") ", bEndpoint, dLength);
 
 /*    int i;
     for (i = 0; i < dLength; i++) {
@@ -983,7 +983,7 @@
         }
     }
 
-    TRACE_DEBUG_WP("AddW%d(%d) ", bEndpoint, dLength);
+    TRACE_DEBUG_WP("AddW%d(%" PRIu32 ") ", bEndpoint, dLength);
 
     /* Add buffer to buffer list and update index */
     pTx = &(pMbl->pMbl[pMbl->inCurr]);
@@ -1047,7 +1047,7 @@
 
     /* Endpoint enters Receiving state */
     pEndpoint->state = UDP_ENDPOINT_RECEIVING;
-    TRACE_DEBUG_WP("Read%d(%d) ", bEndpoint, dLength);
+    TRACE_DEBUG_WP("Read%d(%" PRIu32 ") ", bEndpoint, dLength);
 
 /*    int i;
     for (i = 0; i < dLength; i++) {
@@ -1094,7 +1094,7 @@
     status = UDP->UDP_ISR;
     status &= UDP->UDP_IMR;
     
-    TRACE_DEBUG("status; 0x%x", status);
+    TRACE_DEBUG("status; 0x%" PRIx32 , status);
 
     if (USBD_GetState() < USBD_STATE_POWERED) {
 
diff --git a/sam3s_example/atmel_softpack_libraries/libchip_sam3s/source/pio_it.c b/sam3s_example/atmel_softpack_libraries/libchip_sam3s/source/pio_it.c
index c5351e8..48403c0 100644
--- a/sam3s_example/atmel_softpack_libraries/libchip_sam3s/source/pio_it.c
+++ b/sam3s_example/atmel_softpack_libraries/libchip_sam3s/source/pio_it.c
@@ -104,7 +104,7 @@
     /* Check pending events */
     if ( status != 0 )
     {
-        TRACE_DEBUG( "PIO interrupt on PIO controller #%d\n\r", id ) ;
+        TRACE_DEBUG( "PIO interrupt on PIO controller #%" PRIu32 "\n\r", id ) ;
 
         /* Find triggering source */
         i = 0;
@@ -119,7 +119,7 @@
                 /* Source has PIOs whose statuses have changed */
                 if ( (status & _aIntSources[i].pPin->mask) != 0 )
                 {
-                    TRACE_DEBUG( "Interrupt source #%d triggered\n\r", i ) ;
+                    TRACE_DEBUG( "Interrupt source #%" PRIu32 " triggered\n\r", i ) ;
 
                     _aIntSources[i].handler(_aIntSources[i].pPin);
                     status &= ~(_aIntSources[i].pPin->mask);
@@ -231,7 +231,7 @@
     assert( _dwNumSources < MAX_INTERRUPT_SOURCES ) ;
 
     /* Define new source */
-    TRACE_DEBUG( "PIO_ConfigureIt: Defining new source #%d.\n\r",  _dwNumSources ) ;
+    TRACE_DEBUG( "PIO_ConfigureIt: Defining new source #%" PRIu32 ".\n\r",  _dwNumSources ) ;
 
     pSource = &(_aIntSources[_dwNumSources]) ;
     pSource->pPin = pPin ;
diff --git a/sam3s_example/atmel_softpack_libraries/libchip_sam3s/source/pmc.c b/sam3s_example/atmel_softpack_libraries/libchip_sam3s/source/pmc.c
index b71d748..fa4dde0 100644
--- a/sam3s_example/atmel_softpack_libraries/libchip_sam3s/source/pmc.c
+++ b/sam3s_example/atmel_softpack_libraries/libchip_sam3s/source/pmc.c
@@ -63,7 +63,7 @@
     {
         if ( (PMC->PMC_PCSR0 & ((uint32_t)1 << dwId)) == ((uint32_t)1 << dwId) )
         {
-            TRACE_DEBUG( "PMC_EnablePeripheral: clock of peripheral"  " %u is already enabled\n\r", dwId ) ;
+            TRACE_DEBUG( "PMC_EnablePeripheral: clock of peripheral"  " %" PRIu32 " is already enabled\n\r", dwId ) ;
         }
         else
         {
@@ -75,7 +75,7 @@
         dwId -= 32;
         if ((PMC->PMC_PCSR1 & ((uint32_t)1 << dwId)) == ((uint32_t)1 << dwId))
         {
-            TRACE_DEBUG( "PMC_EnablePeripheral: clock of peripheral"  " %u is already enabled\n\r", dwId + 32 ) ;
+            TRACE_DEBUG( "PMC_EnablePeripheral: clock of peripheral"  " %" PRIu32 " is already enabled\n\r", dwId + 32 ) ;
         }
         else
         {
@@ -100,7 +100,7 @@
     {
         if ( (PMC->PMC_PCSR0 & ((uint32_t)1 << dwId)) != ((uint32_t)1 << dwId) )
         {
-            TRACE_DEBUG("PMC_DisablePeripheral: clock of peripheral" " %u is not enabled\n\r", dwId ) ;
+            TRACE_DEBUG("PMC_DisablePeripheral: clock of peripheral" " %" PRIu32 " is not enabled\n\r", dwId ) ;
         }
         else
         {
@@ -112,7 +112,7 @@
         dwId -= 32 ;
         if ( (PMC->PMC_PCSR1 & ((uint32_t)1 << dwId)) != ((uint32_t)1 << dwId) )
         {
-            TRACE_DEBUG( "PMC_DisablePeripheral: clock of peripheral" " %u is not enabled\n\r", dwId + 32 ) ;
+            TRACE_DEBUG( "PMC_DisablePeripheral: clock of peripheral" " %" PRIu32 " is not enabled\n\r", dwId + 32 ) ;
         }
         else
         {
diff --git a/sam3s_example/atmel_softpack_libraries/usb/device/core/USBD.c b/sam3s_example/atmel_softpack_libraries/usb/device/core/USBD.c
index 3613007..3630c05 100644
--- a/sam3s_example/atmel_softpack_libraries/usb/device/core/USBD.c
+++ b/sam3s_example/atmel_softpack_libraries/usb/device/core/USBD.c
@@ -108,8 +108,7 @@
         deviceState = previousDeviceState;
         if (deviceState >= USBD_STATE_DEFAULT) {
             /* Invoke the Resume callback */
-            if (USBDCallbacks_Resumed)
-                USBDCallbacks_Resumed();
+            USBDCallbacks_Resumed();
         }
     }
 }