nrf52832 mesh bricks after OTA update

Question

Hello, 
 for clarification I use the nrf5_SDK_for_Mesh_v2.1.1. 
 After an OTA update (with use of the nRF toolbox app) the nrf52832 seem to be in a state of constant reboots. After some digging I see that the error happens during the mesh initialization in the "flash_manager_add()" function located at "flash_manager.c". In my case the when updating through OTA the "flash_area_is_valid()" will turn false. In addition the following is written in the function " If the area build fails, it's because we can't fit all the metadata in the action queue. Consider increasing its size. " 
 What can I do to fix this issue? How can I increase this action queue size? Am I looking in the right direction or am I just fixing a symptom instead of the cause?

Edvin · Accepted Answer

I see that in SDK15.0.0, the variable is called DFU_APP_DATA_RESERVED, and is defined in nrf_dfu_types.h. 
 
 Yes, NRF_DFU_SINGLE_BANK_APP_UPDATES set to 1 may prevent the issue to some degree, but if the application is big enough, the bootloader would start writing over your DFU area instead of throwing an error saying that the app is too big, so I would recommend you set the DFU_APP_DATA_RESERVED correctly. 
 The reason NRF_DFU_SINGLE_BANK_APP_UPDATES 1 works is that the bootloader will not try to use dual bank, meaning it will delete the application and store the application in the direct placement at first. In this case, it meant that the bootloader didn't use the area of the FDS pages. When it tried to use dual bank, it stored the application in the flash after the original application, because it thought it had space, since the flash manager pages was not protected by DFU_APP_DATA_RESERVED. 
 
 Dual bank is better if possible, because then you have a rollback in case something goes wrong during DFU (power loss). If not, the fallback after that would be that the device will start advertising as DfuTarg instead of running the previous application. No crisis, but it is a nice-to-have feature. 
 
 So the conclusion is: Set DFU_APP_DATA_RESERVED to protect your flash manager pages. It is a good safety to have, preventing bricked devices, like the update you currently had lead to (if you didn't have a programmer). 
 
 Best regards, 
 Edvin

nrf52832 mesh bricks after OTA update

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