Preserving application data with growing bootloader

Question

Application data is stored just before the bootloader. If I do a DFU upgrade with a larger bootloader than the one currently flashed, is this taken care of? That is, is the application data copied to the area just before the new bootloader? 
 I've read infocenter.nordicsemi.com/index.jsp but this little (but very important) detail isn't mentioned. 
 Using SDK v13.0.0 and nRF52. 
 Thanks, Jacob

Hung Bui · Accepted Answer

Hi Jacob, 
 Enlarging the size of the bootloader is not really supported with our bootloader, at least not out of the box. 
 The reason for that is the address of the bootloader is written in UICR. It's possible to erase the UICR and write new address to it but this is not handled by the current bootloader. (on nRF51 it was not possible to erase UICR). 
 Therefore reserving the data when enlarging the bootloader is also not handled with our current bootloader. 
 My suggestion is to reserve enough space for the bootloader so that you don't have to move the bootloader address down in flash when you enlarging it in the future.

Preserving application data with growing bootloader

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