Start of application takes ages after DFU process is complete

[ste2108]

Hello,

in my application (SDK 16.0.0, nRF52840) I perform a DFU and successfully update the application firmware. However I have noticed that from the moment when the DFU is complete (i.e. the moment when the on_dfu_complete callback, defined in nrf_dfu_req_handler.c, is executed) to the moment when my application is active there is a huge time gap, about 15 seconds. Do you have any idea about the cause of this gap and how to reduce it? My guess is that there is either a coherence check on the new application before it is started, or a specific parameter that causes the delay in the sdk_config.h, which I am not aware of. My application occupies little less than half the available flash on the 52840.

Thank you.

Kind regards,

Stefano

[ste2108]

Dear Vidar,

Thank you for your answer. I need the bootloader to signal a successful firmware update to the application, and I am presently doing it by setting a bit of the gpregret register in the  on_dfu_complete callback. The problem is that, in case an hard reset (e.g. shutdown) happens during the period when the firmware is moved from bank 1 to bank 0, the gpregret bit will be reset (whereas the shift from bank 1 to bank 0 will be finalised anyway, once the device is repowered). A simple solution would be to move the setting of the gpregret bit to the end of the fw validation, after the 13 seconds discussed above. Could you please tell me which is the best point to do that?

Thank you.

Kind regards,

Stefano

[Vidar Berg]

Maybe after app_active() returns with NRF_SUCCESS here: 

[ste2108]

After looking at the function you suggested I thought it could be better to add the gpregret write operation after it is called in nrf_bootloader_init (nrf_bootloader.c). Do you see anything wrong with it? I tested it and it seems ok, which means that now even if I switch the board off during the bank1 validation and shift to bank0, the gpregret bit is eventually set and my application can use it once it has started. 

Thanks.

Regards,

Stefano

[Vidar Berg]

Hi Stefano,

It depends if you want your flag to also be set after a Softdevice or bootloader update.

Regards,

Vidar

[ste2108]

no, just after a successful application update. Ok thanks, I'll close the ticket.