DFU Post Validate Fails at CRC16

[Dave_couling]

Hi guys,

I've almost got DFU working on SDK10. However I am having issues at post validation of the image, specifically in the function dfu_init_postvalidate() in file dfu_init_template.c. In this function the CRC passed from the init file is compared to the locally calculated CRC via a crc16_compute() call. However this function does not seem to return a matching value. I know the init file has the correct the CRC of my image and it is correctly passed to the bootloader. However every time, the locally calculated CRC does not match (incorrect). I could easily bypass this step, but I'd rather keep it for an image integrity check.

If directly DFU the .hex file without .zip generation via NrfStudio I see that nrfStudio sends the same CRC calculation as my .zip file. So the only possible source of error is in the local crc16_compute() . How is crc16_compute() different from the way nrf.exe calculates the CRC? Has anyone faced this issue?

Thanks guys,

DC

[tesc]

Hi,

• crc16_compute() is found in <sdk folder>\components\libraries\crc16\crc16.c
• The function used for nrfutils.exe and nRFgo Studio is calc_crc16(), which is published on GitHub

The functions are equivalent.

Regards, Terje

[tesc]

• Do you get this crc mismatch using an SDK example, or is it a custom project?
• Are you able to reproduce using an SDK example?

[Dave_couling]

This is bizarre because they are definitely returning different results on the same image. I tested calculations but at Bank 1 and Bank 0 in case something occured during the swap. It occurs when the image is encrypted. The nrf.exe calculates the same CRC as nrfStudio on the encrypted image. But the crc16_compute() does not seem to calculate the correct CRC. This suggests that the functions you mentioned are difference in how they calculate.

[tesc]

I can have a deeper look into this if you provide me with the project and the related files and information for how to reproduce. If you need confidentiality you can create a case on My page, where you attach the project. (Register a user for My page here if you do not already have one.)

[Dave_couling]

I was simply using the SDK 10 bootloader example project. I generated the zip and init file via nrf.exe (which matched the nrfStudio auto-init CRC generation). Via debugging on the dfu_init_postvalidate() function I saw that the received and correct CRC does not match the one calculated via crc16_compute(). I'm not sure I'm allow to share our encrypted image however. I'll see