What will happen if the bootloader DFU failed?

[oplinux]

Dear friends,

We want to update the bootloader in our project. I have read the tutorial about the DFU process from here "Dual-bank and single-bank updates ". I have some questions about this DFU process, as below,

a) "After validation, the new SoftDevice and the new bootloader are copied to replace the existing firmware. " 

    When we copied the new bootloader to replace the  old one, the copy process breaked by power-off,  will the DFU process recover when reset ?

b) Who is responsible for the process of copying the bootloader and SoftDevice to replace the old one?

Thank you in advance.

[Einar Thorsrud]

Hi,

Who is responsible for the process of copying the bootloader and SoftDevice to replace the old one?

Bootloader and SoftDevice updates are always dual bank, and the copying itself is handled by the MBR, which itself is never updated.

When we copied the new bootloader to replace the  old one, the copy process breaked by power-off,  will the DFU process recover when reset ?

If a reset happens during copying, the MBR will see that the bootloader update was not completed and it will continue to copy it in place. This mechanism is safe in the sense that there is never a time where a reset will brick the device.

[oplinux]

Thank you so much Einar.

The mechanism is so clever.

Could you tell me which tutotial has detailed introduce about this process "Bootloader and SoftDevice updates are always dual bank, and the copying itself is handled by the MBR"?

[Einar Thorsrud]

Hi,

The closest you get in the documentation is Master boot record and SoftDevice reset procedure within the MBR doc, which states: "If an in-system bootloader update procedure is in progress: The in-system update procedure continues its execution."

Other than that, this is not documented anywhere in detail, unfortunately. You can the other information about the MBR in the Softdevice specification, including the API doc. Specifically the bootloader copying is done using the SD_MBR_COMMAND_COPY_BL command. The way this works is that the MBR writes the command and state to the MBR params page, which is the second to last page, between the end of the bootloader and the bootloader settings page. This is persistent and allows the MBR to keep track of the state between resets and possible power cycles etc.

[oplinux]

Thank you so much, I will read the documentation you mentioned above,thanks agin.