Debugging on nRF52833 with IAR when using DFU and APPPROTECT

[Federico]

Hi,

I'm developing on the current setup:

• nRF52833 DK, emulating an nRF52820. 
• Soft Device 113 version 7.2.0
• SDK 17.1.0
• IAR EW ARM 9.30

I'm trying to include the secure bootloader code into our project based on the example " \examples\dfu\secure_bootloader\pca10100e_s112_ble". 

I believe the APPPROTECT and IAR are putting me in some sort of deadlock. The Bootloader guide on the documentation (Nordic Semiconductor Infocenter) says that: "You cannot write to MBR_UICR_BOOTLOADER_ADDR when using the default J-Link target driver in IAR. Therefore, you must set up nrfjprog as an external tool". 

So I'm flashing the bootloader image (the output of the pca10100e_s112_ble project) via command line using jprog. However, when I try to debug from IAR, I get a message prompt saying that "CTRL-AP indicates that the device is secured. For debugger connection the device needs to be unsecured. Note: unsecuring will trigger a mass erase of the internal flash.". So obviously when I press "Yes" the bootloader image gets erased. 

Can I disable this device "secure" mode (which I believe is APPROPTECT) permanently? Is there any other way to work around this?

Thank you!

[Vidar Berg]

Hi,

The AP protection is supposed to be disabled on startup here: https://github.com/NordicSemiconductor/nrfx/blob/v1.9.0/mdk/system_nrf52_approtect.h#L53. However, due to an unfortunate bug in the MDK version (v8.40.3) bundled with nRF5 SDK 17.1.0, the nrf52_errata_249() function  ends up returning false even when it is run on  nrf52833 rev.2 with the hardened approtect mechanism ([249] DIF: Access port protection needs software interface configuration)

This issue was addressed in MDK version 8.44.2 (https://www.nordicsemi.com/Products/Development-tools/nRF-MDK ):

So, the fix for this is to download MDK version 8.44.2 or later (https://www.nordicsemi.com/-/media/Software-and-other-downloads/Desktop-software/nRF-MDK/sw/8-51-0/nRF_MDK_8_51_0_GCC_NordicLicense.zip) and replace the files in nRF5_SDK_17.1.0_ddde560/modules/nrfx/mdk with the ones you downloaded and rebuild the application/bootloader.

Before flashing the board for the first time, you should also run "nrfjprog --recover". This will write 0x5A  to the non-volatile UICR.APPROTECT register so the readback protection stays disabled across resets.

Best regards,

Vidar

[Federico]

Thanks! This worked great