DFU .dat file checksum verification

[Pierre cgwi22]

Hello,

We are using nRF52840 with SDK 15.2.0, a bootloader and the SoftDevice. We are able to perform a DFU by downloading the .bin and .dat files of the new firmware in Flash memory, to fill the DFU settings structure with the correct values, and after a reboot the bootloader updates our firmware as expected.

All of this works if the files are correctly downloaded, but if a data corruption happens we currently don't verify the checksum before the reboot, so the new firmware is not able to start.

This is the reason why we want to check the .bin file received, using the informations contained in the .dat file. We have computed the checksum of the .bin data, but we can't find informations about the data structure of the .dat file to be able to compare the checksums. Where is located the expected .bin checksum in the .dat file?

Thanks for your help!

[Amanda Hsieh]

Hi Pierre, 

Bootloader needs to know the checksum value of the application image in order to validate it on boot, and will fall back to DFU mode if it is unable to verify it.  The checksum value along with other flags are stored in the bootloader settings page. You can take a look at BLE Secure DFU Bootloader on how to check CRC. 

-Amanda H.

[Pierre cgwi22]

Hi Amanda, thanks for your answer.

Finally we have found the solution. With the help of the command "nrfutil pkg display my_file.zip" we have been able to discover where the SHA-256 hash of the .bin data is located in the .dat data. So now we can compute the hash of the .bin file and compare it to the expected hash in the .dat file.

Our problem is solved.