DFU Bootloader uploading smaller App

[MM-MUC]

Hi,

we have a NRF52832 based project / product. We are using a DFU bootloader for application and SD update. The update is done from a master microcontroller using UART.

Our update packages are created using the Nordic Tools and uploaded to the master microcontroller via ftp. All that is working just fine. 

We just have one problem: If we update the application with a smaller file than the one that is installed, the update fails. The bootloader reports "nrf_dfu_validation: Hash verification failed."

It looks like the hash is generated over a larger area of flash than the size of the application itself. When the application that has been installed before is smaller there seems to be a rest of the old application in the flash memory and the hash generation fails.

What can be done to avoid this problem?

[MM-MUC]

Hi Vidar,

I agree, as the flash is written in 4096 Byte pages it's really strange that this happens. 

Usually that won't even be a problem as the size of an application normally increases. I only came across the problem after removing some debug RTT_printfs.

I will try reading the flash later today and let you know what I can see.

Marcus

[MM-MUC]

Hi Vidar,

very strange, I just tested it again. Now after the initial flash was done with the short version of the file, everything is fine I can flash short and long files back and forth without any problems.

No idea what was happening before, when I initially installed (via nrfjprog) the file with the long application.

Marcus

[Vidar Berg]

Hi Marcus,

Thank you for the update. I'm afraid I can't think of any explanation for this either. Please update the ticket if you manage to reproduce this again and collect more debug more information.

Vidar

[MM-MUC]

Hi Vidar,

I tried to reproduce that behaviour today. However, in the meantime to much changed on the side of our master microcontroller and that code is no longer compatible with the bootloader. Rolling back all that would be to time consuming. Therefore I hope the problem was just an isolated incident.

Marcus