kind of works for writing flash. IMPORTANT ISSUE - the memory usage output given by the linker for program size used DOES NOT equal the actual flash space used when programming. INVESTIGATE: did I set a memory space that doesn't lie on a page boundary? or do I just need to increase the flash space allocated to the bootloader

bootloader/src/main.c

@@ -9,22 +9,75 @@
 #include "usb.h"
 #include "bootloader.h"
 
-void main(void) {
-    //UserInit();
+/* Private prototypes */
+void main(void);
+void BootMain(void);
+
+const unsigned int FlashSignatureWord __at(APP_SIGNATURE_ADDRESS) = APP_SIGNATURE_VALUE;
+
+void main(void)
+{
+    //BootMain();
+    /**
+     * TODO: implement hardware IO-based method for forcing entry into bootloader
+     */
     
+    // normal operation: verify the firmware signature is valid. if it isn't enter
+    // bootloader (fw update) mode so valid firmware can be flashed
+//DoFlashSignatureCheck:
+    //Check if the application region flash signature is valid
+    if(*(const unsigned int*)APP_SIGNATURE_ADDRESS == APP_SIGNATURE_VALUE)
+    {
+        //The flash signature was valid, implying the previous
+        //erase/program/verify operation was a success.
+
+        //Also make sure the first WORD of program memory in the app space
+        //is not blank, meaning there is an application image programmed into the device.
+        if(*(const unsigned int*)REMAPPED_APPLICATION_RESET_VECTOR != 0xFFFF)
+        {
+            //Go ahead and jump out of bootloader mode into the application run mode
+            #asm
+                goto REMAPPED_APPLICATION_RESET_VECTOR
+            #endasm
+        }
+    }
+    //else the application image is missing or corrupt.  In this case, we
+    //need to stay in the bootloader mode, so the user has the ability to
+    //try (again) to re-program a valid application image into the device.
+    
+    BootMain();
+}
+
+void BootMain(void) __at(0x30)
+{
+    //Make sure interrupts are disabled for this code (could still be on,
+    //if the application firmware jumped into the bootloader via software methods)
+    INTCON = 0x00;
+
+    //Clear the stack pointer, in case the user application jumped into 
+    //bootloader mode with excessive junk on the call stack
+    STKPTR = 0x00;  
+
+    // End of the important parts of the C initializer.  This bootloader firmware does not use
+    // any C initialized user variables (idata memory sections).  Therefore, the above is all
+    // the initialization that is required.
+
     // initialize the USB framework
     USBDeviceInit();
     USBDeviceAttach();
     
+    // initialize the bootloader
+    UserInit();
+    
+    //Execute main loop
     while(1)
     {
+        //Need to call USBDeviceTasks() periodically.  This function takes care of
+        //processing non-USB application related USB packets (ex: "Chapter 9" 
+        //packets associated with USB enumeration)
         USBDeviceTasks();
         
-        // do nothing if: not connected to USB host, or the host put us in suspend state
-        if((USBGetDeviceState() < CONFIGURED_STATE) | USBIsDeviceSuspended())
-            continue;
-
-        // run application specific tasks
-        ProcessIO();
-    }
-}
+        ProcessIO();        //This is where all the actual bootloader related data transfer/self programming takes
+                            //place see ProcessIO() function in the BootPIC[xxxx].c file.
+    }//end while    
+}