serial DFU update with SD+BL+APP

[kevinlam]

Hello,

According to the description in below page, "The image can be an application image, SoftDevice image, bootloader image, or a combined image of bootloader and SoftDevice."

https://infocenter.nordicsemi.com/index.jsp?topic=%2Fcom.nordic.infocenter.sdk5.v14.2.0%2Fsdk_app_serial_dfu_bootloader.html&cp=4_0_0_4_4_2 

Does it mean if DFU (SD+BL+APP) altogether, I have to do DFU twice? Firstly DFU (SD+BL) and then DFU (APP)?

And also when DFU the soft device, is it possible to upgrade / downgrade if the major version is different? for example DFU from 15.2 to 16 / 16 back to 15.2? 

Thanks!

Kevin

[Einar Thorsrud]

Hi Kevin,

Does it mean if DFU (SD+BL+APP) altogether, I have to do DFU twice? Firstly DFU (SD+BL) and then DFU (APP)?

No, that is an inaccurate statement in the documentation. You can have a combination of SD+BL+APP in a single image. However, the update will be split in two, first the SD + BL, then the APP, but this will not be visible to the end-user.

And also when DFU the soft device, is it possible to upgrade / downgrade if the major version is different? for example DFU from 15.2 to 16 / 16 back to 15.2? 

As a general rule yes, you can upgrade from one SDK version to another, though there may be some issues with some combinations, particularly if the bootloader has changed in size since the bootloader start address is fixed. As long as you use the same bootloader start address moving between 15.2 and 16 is no problem. (Just remember that the DFU image must have a higher version than the existing for the bootloader to allow the update (unless you remove this limitation), but that is a version number you provide to nrfutil and not related to the SDK version or anything else.)

Einar