nRF52 DK bricked after enabling code protection in firmware

[Chaswb]

This is a project using nRF52832.

On nRF connect SDK, we want to ensure that firmware does not get shipped without read-back protection enabled. During development I have CONFIG_NRF_APPROTECT_LOCK=n in prj.conf, as otherwise debugging isn't possible. This is a risk, as we have to ensure it's rebuilt with prj.conf changed. I added the following to my code which gets called if 

NRF_UICR->APPROTECT isn't 0xff:

 

    volatile uint32_t *reg;

    reg = &NRF_NVMC->CONFIG;

    *reg = 0x1;

    reg = &NRF_UICR->APPROTECT;

    *reg = 0xffffff00;

    reg = &NRF_NVMC->CONFIG;

    *reg = 0;

Originally I didn't write to NRF_NVMC->CONFIG, but then the write to NRF_UICR->APPROTECT had no effect.

Since doing this, it's not possible to unprotect the code, either using nrfjprog --recover in VSCode, or nRF Connect for desktop Erase all.

I'm using Windows 10 Pro version 22H2

The toolchain is v2.4.1

nRF connect desktop is v4.3.0

[Sigurd Hellesvik]

Hi,

Give me a
nrfjprog --version

Regards,
Sigurd Hellesvik

[Chaswb]

nrfjprog version: 10.24.1 external
JLinkARM.dll version: 7.94e

[Sigurd Hellesvik]

Hm, those seem new enough for this not to be an issue to me.

The nRF52832 should always be recoverable with nrfjprog --recover.

Can you try to in the VS Code Extension open a new "nRF Connect" terminal for the hello world project and run "west flash --erase --recover"?

[Chaswb]

Thanks. That worked and the board is now unbricked.

The west command doesn't work from my project, but does from the hello_world project. I got "--build-dir was not given".
One thing to note is that the terminal has to be a nRF Connect terminal, and not a powershell one

[Sigurd Hellesvik]

Chaswb said:

Thanks. That worked and the board is now unbricked.

Nice!

The west command does stuff in a particular order, so I often use it as a fallback to fix things.