diff --git a/openrtx/include/interfaces/keyboard.h b/openrtx/include/interfaces/keyboard.h
index fade32c1..4534eb4d 100644
--- a/openrtx/include/interfaces/keyboard.h
+++ b/openrtx/include/interfaces/keyboard.h
@@ -59,8 +59,7 @@ enum keys
     KEY_F9    = (1 << 27),  /* Function button (device specific) */
     KEY_F10   = (1 << 28),  /* Function button (device specific) */
     KEY_F11   = (1 << 29),  /* Function button (device specific) */
-    KEY_F12   = (1 << 30),  /* Function button (device specific) */
-    KEY_F13   = (1 << 31)   /* Function button (device specific) */
+    KEY_F12   = (1 << 30)  /* Function button (device specific) */
 };
 
 /**
diff --git a/platform/mcu/STM32F4xx/drivers/usb/usb_core.c b/platform/mcu/STM32F4xx/drivers/usb/usb_core.c
index 12a207d8..2521449e 100644
--- a/platform/mcu/STM32F4xx/drivers/usb/usb_core.c
+++ b/platform/mcu/STM32F4xx/drivers/usb/usb_core.c
@@ -29,6 +29,15 @@
 #include "usb_core.h"
 #include "usb_bsp.h"
 
+/* Workaround to suppress -Wattributes warning */
+struct __attribute__((packed, aligned(1))) T_UINT32_WRITE { uint32_t v; };
+#define __UNALIGNED_UINT32_WRITE(addr, val) \
+        (void)((((struct T_UINT32_WRITE *)(void *)(addr))->v) = (val))
+
+struct __attribute__((packed, aligned(1))) T_UINT32_READ { uint32_t v; };
+#define __UNALIGNED_UINT32_READ(addr) \
+        (((const struct T_UINT32_READ *)(const void *)(addr))->v)
+
 
 /** @addtogroup USB_OTG_DRIVER
 * @{
@@ -180,7 +189,7 @@ USB_OTG_STS USB_OTG_WritePacket(USB_OTG_CORE_HANDLE *pdev,
     fifo = pdev->regs.DFIFO[ch_ep_num];
     for (i = 0; i < count32b; i++, src+=4)
     {
-      USB_OTG_WRITE_REG32( fifo, *((__packed uint32_t *)src) );
+      USB_OTG_WRITE_REG32( fifo, __UNALIGNED_UINT32_READ(src) );
     }
   }
   return status;
@@ -205,7 +214,7 @@ void *USB_OTG_ReadPacket(USB_OTG_CORE_HANDLE *pdev,
   
   for ( i = 0; i < count32b; i++, dest += 4 )
   {
-    *(__packed uint32_t *)dest = USB_OTG_READ_REG32(fifo);
+    __UNALIGNED_UINT32_WRITE(dest, USB_OTG_READ_REG32(fifo));
     
   }
   return ((void *)dest);
diff --git a/platform/mcu/STM32F4xx/drivers/usb/usb_dcd_int.h b/platform/mcu/STM32F4xx/drivers/usb/usb_dcd_int.h
index 69e525a2..c50b7eee 100644
--- a/platform/mcu/STM32F4xx/drivers/usb/usb_dcd_int.h
+++ b/platform/mcu/STM32F4xx/drivers/usb/usb_dcd_int.h
@@ -59,10 +59,10 @@ typedef struct _USBD_DCD_INT
   uint8_t (* Resume) (USB_OTG_CORE_HANDLE *pdev);
   uint8_t (* IsoINIncomplete) (USB_OTG_CORE_HANDLE *pdev);
   uint8_t (* IsoOUTIncomplete) (USB_OTG_CORE_HANDLE *pdev);  
-  
+#ifdef VBUS_SENSING_ENABLED
   uint8_t (* DevConnected) (USB_OTG_CORE_HANDLE *pdev);
   uint8_t (* DevDisconnected) (USB_OTG_CORE_HANDLE *pdev);   
-  
+#endif
 }USBD_DCD_INT_cb_TypeDef;
 
 extern USBD_DCD_INT_cb_TypeDef *USBD_DCD_INT_fops;
diff --git a/platform/mcu/STM32F4xx/drivers/usb/usbd_req.c b/platform/mcu/STM32F4xx/drivers/usb/usbd_req.c
index 39c6570a..0174a6cb 100644
--- a/platform/mcu/STM32F4xx/drivers/usb/usbd_req.c
+++ b/platform/mcu/STM32F4xx/drivers/usb/usbd_req.c
@@ -826,7 +826,7 @@ void USBD_GetString(uint8_t *desc, uint8_t *unicode, uint16_t *len)
     unicode[idx++] = *len;
     unicode[idx++] =  USB_DESC_TYPE_STRING;
     
-    while (*desc != NULL) 
+    while (*desc != 0)
     {
       unicode[idx++] = *desc++;
       unicode[idx++] =  0x00;
@@ -844,7 +844,7 @@ static uint8_t USBD_GetLen(uint8_t *buf)
 {
     uint8_t  len = 0;
 
-    while (*buf != NULL) 
+    while (*buf != 0)
     {
         len++;
         buf++;