nRF52 APPPROTECT

[Eric Stutzenberger]

Hi,

Is there a way on the nRF52 to clear the APPPROTECT bits once they have been set?

On the nRF51, it was still possible to erase the chip to clear the readback protection. However, on the nRF52, the APPPROTECT bits seem to fully disable the debugger.

Thanks,

Eric

[David García Polo]

The public documentation of the unprotection mechanism is missing, but you can either do:

1. Use nrfjprog.exe -f NRF52 --recover
2. Use nrfjprog.dll function recover() or use the pynrfjprog recover()
3. Manually, a) write 1 to register 0x4 of debug access port 1, b) read register 0x8 of debug access port until its value is 0, c) write 0 to register 0x4 of debug access port 1, d) write 1 to register 0x0 of debug access port 1, e) write 0 to register 0 of debug access port 1.

I understand that option 3 is the only option available if you do not use nrfjprog. What do you use?

[Eric Stutzenberger]

I was able to use option 1. It is not that option 3 is the only one available to me but that I was unaware of the trick with nrfjprog.exe. When using nRF Go Studio and trying to recover a board with app protect bits set, the Recover button is disabled.

Is there a plan to improve this erasure method? I ask because we program firmware in our factory to our modules that we want protected. However, we also want customers to be able to easily erase the part. I was unable to access the part with nRF Go Studio. Perhaps this is a change that has not yet been made to it?