Questions about upgrade Bootloader OTA

[Liu Tengfei]

Hi support team,

I'm using a PDK(PCA10056) with nrf52840 and SDK 15.0. Recently I was developing a BLE bootloader for DFU OTA. 

Since the ble bootloader was depended on softdevice, if I want to update softdevice to another major version which will probably be incompatible with the current bootloader on my chip, I have to update the bootloader & softdevice at the same time, right? Otherwise, if only one of them was updated, bootloader could not be able to work.

I have three questions:

1. Is the MBR a part of softdevice in SDK 15.0?

If MBR was a part of softdevice, so I don't need to program MBR separately if I have programmed softdevice? If not, who will be responsible to forward interrupt to softdevice and enable it at startup?

2. Will my device get bricked when power off happened during swapping flash data in upgrading bootloader itself?

3. The process flow of updating bootloader with softdevice,

My understanding is, bootloader is responsible to handle and receive the dfu package data(include bootloader and softdevice) OTA, and then bootloader will finally write new softdevice to the flash and overwrite the old one. After that, MBR will be responsible to write new bootloader to flash, right?

[Susheel Nuguru]

Hi,

Apologies for the late reply, something this thread missed our sight.

1) MBR is part of softdevice release, yes. You do not need to update MBR if you update the softdevice.

2) The device is not bricked. MBR/bootloader are able to detect and abrupt power loss during DFU and are able to recover from that situation. Look into the thread here

3) The statemachine and process is explained here

Your understanding is correct about MBR/Bootloader responsibilities.