DFU over BLE using slots on external flash

[Sankton]

Hello Hi Greetings 
This Ticket is regarding documentation and configuration on DFU over BLE using slots on external flash.


We are using 52833soc based custom board that has SPI flash .
We thought that suppose the new firmware upgrade won't have enough memory in soc flash to store , so we thought we can use external flash to store new firmware image and then do the swapping .


I am here to seek direction . 
Please can you tell me a flowchart like how I should approach this task .
like first I think I should study boot loaders and see what's MCUboot and what's nrf's secure boot .

I feel a flowchart / numbered points from a specialist will help more , that raising tickets all the time . So please help me with this , like what should be done first like partitioning or setting up MCUboot .

After that please provide me the link of sample example (if its there ) that does this operation .

Thanks 

S

[Amanda Hsieh]

Hi, 

like first I think I should study boot loaders and see what's MCUboot and what's nrf's secure boot .

 See the Quick start guide and this Bootloaders and DFU/FOTA course. 

Please can you tell me a flowchart like how I should approach this task .

To update via BLE DFU with SPI external flash on nRF52833, you should make sure the SPI external flash works as expected at first. Here is a sample. You can take a look at the settings: nrf52840dk_nrf52840_spi.conf and nrf52840dk_nrf52840_spi.overlay and adopt them for your nRF52833 custom board. 

Then, To use the SPI external flash as the second slot, it needs:

• Enable mcuboot, you can use sysbuild_fota.conf to include sysbuild configs. 
• These external SPI settings are for the app configuration. 
• The board overlay file looks like this for the app. 
• These external SPI setting (under sysbuild/mcuboot) are for the mcuboot.
• The board overlay file looks like this for the mcuboot.  

Before you start the work, I highly recommend you take a look at the Bootloaders and DFU/FOTA course to know how the mcuboot and DFU work in the NCS, and use nRF52840DK to familiarize yourself with the flow and setting, then move to your custom board.  

Regards,
Amanda H.

[Sankton]

oh lord thanks for such beautiful explanation and direction .
thank you .

I will work exactly as you said and let you know how it fared , super soon 

[Sankton]

Hi Amanda Hsieh 

My question now is when we create separate partition for secondary slot in external flash , do I have to explicitly write new image on secondary slot using write_spi api's or MCUboot bootloader does that for me ?

[Amanda Hsieh]

The mcuboot would do that. 

[Sankton]

also sysbuild_fota.conf & other overlay(https://github.com/nrfconnect/sdk-nrf/blob/v2.7.0/applications/nrf5340_audio/sysbuild/mcuboot/prj_fota.conf#L48-L56) you mentioned this file I have to Create separately in child_image/mcuboot/boards right ?

I don't see any sysbuild folder in my example code of "spi flash"
also im done with setting up spi flash and it worked well , thank you