Secure UART DFU: Can't jump to Application

[tejaChintalapati]

Hi,

I am trying to get Secure UART Bootloader to work and followed the steps mentioned here.

1. I generated the Keys and updated the dfu_public_key.c file in the project at secure_bootloader_uart_mbr_pca10056
2. Erased the chip by going into Target -> Erase All in SES
3. Created the Zip using this command:
   

   nrfutil pkg generate --hw-version 52 --application-version 1 --application myFile.hex --key-file C:\xxxx\xx\xx\xx\priv.pem secureDFUUART.zip --sd-req 0x00

4. Run the DFU using: dfu serial -pkg secureDFUUART.zip -p COM3

What's happening:

1. After the process, nRFUtil says "Device Programmed" and the LED1 and LED3 are turning off.
2. But I can't see the application running on the nRF52840DK

How am I validating that?

• In application, I disabled the Read Access but I can still read back the firmware using J-Flash
• In my app, LED1 toggles and that didn't happen.

Other Information:

1. I can successully do a secure DFU for blinky_pca10056_mbr.hex file following the same steps.
2. This lead me to believe I am missing something in the process of creating the hex file for my custom application.

Can you please help me out to understand what's the problem here?

[Vidar Berg]

Hello,

Please make sure you are using the same linker settings as the blinky_pca10056_mbr project. The application must start at address 0x1000 in flash and not use RAM below 0x20000008 in order to work with the MBR which occupies the first flash page.

[tejaChintalapati]

Thanks Vidar! That makes complete sense.

I followed instructions from this link and updated the Flash start and Ram start per your suggestion and everything's working the way it should.

Appreciate the help.