WIP: Introduce USB DFU code from my at91lib DFU port

firmware/src_board/board_cstartup_gnu.c

@@ -125,6 +125,19 @@ IntFunc exception_table[] = {
     IrqHandlerNotUsed   /* 35 not used */
 };
 
+#if defined (BOARD_USB_DFU) && !defined(dfu)
+static void BootIntoApp(void)
+{
+	unsigned int *pSrc;
+	void (*appReset)(void);
+
+	pSrc = (unsigned int *) ((unsigned char *)IFLASH_ADDR + BOARD_DFU_BOOT_SIZE);
+	SCB->VTOR = ((unsigned int)(pSrc)) | (0x0 << 7);
+	appReset = pSrc[1];
+	appReset();
+}
+#endif
+
 /**
  * \brief This is the code that gets called on processor reset.
  * To initialize the device, and call the main() routine.
@@ -136,6 +149,11 @@ void ResetException( void )
     /* Low level Initialize */
     LowLevelInit() ;
 
+#if defined (BOARD_USB_DFU) && !defined(dfu)
+    if (*(unsigned long *)IRAM_ADDR != 0xDFDFDFDF)
+        BootIntoApp();
+#endif
+
     /* Initialize the relocate segment */
     pSrc = &_etext ;
     pDest = &_srelocate ;
@@ -169,6 +187,9 @@ void ResetException( void )
     /* Branch to main function */
     main() ;
 
+    /* App should have disabled interrupts during the transition */
+    __enable_irq();
+
     /* Infinite loop */
     while ( 1 ) ;
 }