Updating Bootloader to Bootloader Which Preserves App Data

Question

I've recently tried add App Data (pstorage) to my Application. Thus I want to preserve this data over DFU Updates. To do this I updated my Bootloader to reserve App Data during the process via 
 dfu_types.h
#define DFU_APP_DATA_RESERVED 0x0400 
 However when I update from the old Bootloader to the new Bootloader our board completely bricks. Are there any other steps I need to take to instruct the SoC to handle memory? If I merge and program the new Bootloader and App, everything works fine and I can switch into the Bootloader without issue. Its only when I update from the old Bootloader to New Bootloader. Thanks in advance for the help on this. 
 Regards, 
 DC 
 p.s. using SDK 6.2 S110 7.1

Vidar Berg · Accepted Answer

Hi, changing the app data reserved value causes the bank_1 address to change, but unfortunately the bootloader doesn't foresee this change (see dfu_types.h for calculation of bank areas). What happens then is that the new bootloader will tell the MBR to copy the bootloader image once again, but this time using the new bank_1 address even though it still located at the old bank_1 address specified by the old bootloader. The result is that you get a bootloader that lacks the first page of code. 
 I think the easiest solution to this is to modify the dfu_bl_image_validate() function in your new bootloader to check on both the new and the old DFU_BANK_1_REGION_START address. 
 Note, if you're updating to a new softdevice(major release - e.g., 8.x.x) you will have to update BL + SD in the same step due to API differences.

Updating Bootloader to Bootloader Which Preserves App Data

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