NRF52 DK RBP gets enabled without --rbp <...> while flashing with nrfjprog

[Akshay N Kulkarni]

Hi,

I am trying to flash nrf52840 dk board with open thread binaries.

I see that, sporadically the device gets readback protection enabled.

I use the following command to flash hex files:

nrfjprog -f nrf52 -s <serialid> --verify --chiperase --program ot-cli-ftd.hex --reset

Can someone please tell me if I am missing something here?

Why does rbp get enabled without parameter specified for the flashing tool nrfjprog ?

Sometimes, it does not get enabled.

Also, I remember reading about rbp somewhere, UICR registers have limited number of writes and would this be harmful to recover the device every time after RBP is enabled?

Please I am exploring this board and new to it. Kindly help me with this. 

Thank you.

[Håkon Alseth]

Hi,

 

You are most likely using revision 3 devices, which include approtect hardening as per this informational notice #142:

https://infocenter.nordicsemi.com/pdf/in_142_v1.1.pdf?cp=4_2_2_3

 

The fix for this is to use newer startup files (MDK files), which are downloadable from here:

https://www.nordicsemi.com/Products/Development-tools/nRF-MDK

Also, I remember reading about rbp somewhere, UICR registers have limited number of writes and would this be harmful to recover the device every time after RBP is enabled?

As per "Endurance" specification, the chip itself is specified to work with > 10k write/erase cycles:

https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.nrf52832.ps.v1.1/abs_max_ratings.html?cp=4_2_0_4#abs_max_ratings

 

Kind regards,

Håkon