Is DFU expected to work after MCUboot image modification?

[dwalks]

We have devices programed with an 'old' firmware that uses the original larger mcuboot partition. We have always been able to DFU these devices with new firmware.

We have now minimised the mcuboot partition using a child image, and updated the pm_static.yml accordingly.

When flashed with the 'new' firmware the devices function as normal.

If we take devices programmed with the 'old' firmware and attempt a DFU with the 'new' firmware. We find the DFU process completes 'successfully' however the devices no longer boot. Even a debug build connect to RTT produces no output.

Is it expected that the devices continue to work in this scenario? Or should mcuboot partition not be modified between DFU? Our expectation is maybe it should work, since only the application image is updated during the DFU and the application has not increased in size.

Thanks

[Amanda Hsieh]

Hi, 

Do you use the same static partitioning for old/new firmware? See Static partition requirement for DFU

Regards,
Amanda H.

[dwalks]

Hi Amanda,

We are using pm_static.yml to define the partitions. Is that what you mean? In the new firmware the layout was changed  as mcuboot partition was reduced in size. Which is the focus of my question, if that is possible or not.

[Amanda Hsieh]

dwalks said:

We are using pm_static.yml to define the partitions. Is that what you mean?

Yes. 

dwalks said:

In the new firmware the layout was changed  as mcuboot partition was reduced in size. Which is the focus of my question, if that is possible or not.

In such cases, the newly generated application images may no longer use a partition map that is compatible with the partition map used by the bootloader. As a result, the newly built application image may not be bootable by the bootloader.

[dwalks]

Understood, thank you for this.

[Amanda Hsieh]

My pleasure.