nRF52840 readout protection problem

RE: nRF52840 readout protection problem

Vidar Berg — Fri, 05 Aug 2022 11:13:06 GMT

Please check if the UICR.APPROTECT register remains set to HwDisabled/0x5A after you have programmed the Bluetooth FW.

[quote user="nevi"]The error is not consistent. Sometimes the memrd run successfully after programming. Sometimes nrfjpog say this:[/quote]

Have you noticed if the error starts occurring after a pin reset or power on reset? A regular soft reset will not be enough to re-activate the readback protection after a '--recover'.

Note: Register APPROTECT.DISABLE is reset after pin reset, power or brownout reset, watchdog reset, or wake from System OFF as mentioned above. (Access port protection)

RE: nRF52840 readout protection problem

nevi — Thu, 04 Aug 2022 14:23:37 GMT

It's very strange. The error is not consistent. Sometimes the memrd run successfully after programming. Sometimes nrfjpog say this:

ERROR: The operation attempted is unavailable due to readback protection in
ERROR: your device. Please use --recover to unlock the device.
NOTE: For additional output, try running again with logging enabled (--log).
NOTE: Any generated log error messages will be displayed.

Usually if I try to reprogram with --sectorerase it is ok (and then the memrd is also ok), but after I try with --chiperase I get the above error.

The protection problem usually appears when a program that uses the BT stack (SD) is started.
If the program does not start because only the SD has been written, then the error occurs less frequently.

RE: nRF52840 readout protection problem

Vidar Berg — Thu, 04 Aug 2022 13:16:55 GMT

You should not have to update the MDK when using SDK 17.1.0.

[quote user=""]If I program the SD and the app at the same time and then reset, it works. But then I can't debug.[/quote]

What happens when you try to debug, do you get an error message? Also, does nrfjprog claim that readback protection is enabled if you try to access the memory (e.g nrfjprog --memrd 0x0)?

RE: nRF52840 readout protection problem

nevi — Thu, 04 Aug 2022 13:03:38 GMT

I have this:

nrfjprog version: 10.17.0 external
JLinkARM.dll version: 7.66a

I don't really understand this MDK stuff in IN141 Informational Notice v1.1,. Shoud I replace mdk in the nRF5 SDK? Or there is a newer version of the SDK (with this new MDK) . I use the nRF5_SDK_17.1.0_ddde560 and can't find newer.

RE: nRF52840 readout protection problem

Vidar Berg — Thu, 04 Aug 2022 12:57:50 GMT

OK, this should have worked. Please make sure you use an up to date version of nrfjprog as the older versions this not include support for this improved approtect mechanism.

nrfjprog downloads:

https://www.nordicsemi.com/Products/Development-tools/nRF-Command-Line-Tools/Download?lang=en#infotabs

RE: nRF52840 readout protection problem

nevi — Thu, 04 Aug 2022 12:55:18 GMT

I use this:

nrfjprog -f NRF52 --recover
nrfjprog -f NRF52 --program "s140_nrf52_7.2.0_softdevice.hex" --chiperase --verify
nrfjprog -f NRF52 --program "nrf52840_xxaa.hex" --verify --reset

What does this set the APPROTECT register to, hwDisabled or disabled?

RE: nRF52840 readout protection problem

Vidar Berg — Thu, 04 Aug 2022 12:43:17 GMT

Hi,

This is the expected behavior. Please refer to this notice for more details: IN141 Informational Notice v1.1. Basically you need to update the startup files in your existing FW if you want to keep approtect disabled across resets.

Best regards,

Vidar

Edit: Or maybe the HwDisabled value in APPROTECT is being cleared when you program your FW?