Secure Bootloader Downloads app but stays in Bootloader on Custom board

[Kevin s]

My DFU is staying in the bootloader, even after successful download of the application package.

I have modified the secure bootloader for my custom PCB (removed the GPIO for the button check), so that is not an issue.

I can make the DFU "work" if I just initially install the bootloader and softdevice only. The app will start nicely with my app only package.

However, if I generate the combined bootloader, SD and app hex file by manually creating the bootloader settings and adding it to the combined hex file according with the method in Hung Bui's blog ("Getting started with Nordic's Secure DFU bootloader, a step by step guide"), the OTA app will not start and the device stays in the bootloader mode.

When I generate the app package, I have increased the version by "1" over the value I put in the manually generated settings file (from 3 to 4) so it should be setting the app valid flag. I can't debug the bootloader, because I'm using the IAR platform and there seems to be a bug with debugging the bootloader.

Any suggestions to help figure out why the bootloader is not accepting the app would be appreciated.

[bjorn-spockeli]

Hi Kevin, could you post the nrfutil commands you're using to generate the settings hex and the firmware image?

[Kevin s]

Sure, I was in the middle of changing my application version numbers, so now it is 1 and 4.

Also, if I DFU the exact same package twice it works, 3 times no, 4 times yes. Interesting. For the initial programming

nrfutil settings generate --family NRF52 --application app.hex --application-version 1 --bootloader-version 2 --bl-settings-version 1 app_valid.hex

For the update DFU package

nrfutil pkg generate --hw-version 52 --sd-req 0x8C --application-version 4 --application app.hex --key-file ....\OTA_files\private.pem Stick_dfu_r1.3.1.zip

Also for reference, SDK 12.1, SD 3.0.0, IAR 7.70 (workbench 7.5), not sure about MDK

[Kevin s]

More information; I have made another app package; this one with app version 2. It does not matter which package I DFU; it will only go to the app on even number of transfers, no matter which DFU package I download.

[Kevin s]

OK, I put some RGB LED drives in my bootloader and some delays so I could see the LED Color produced for debugging and user purposes and now the DFU is working consistently. Because I'm using a custom board, I took out all the development board led on/off commands. Maybe there was some race condition when I did this....

[bjorn-spockeli]

Ok, so you added some PWM code to your bootloader and that resulted in the bootloader functioning properly?