RE: strange behaviour of nrf5340 dk and zephyr sdk.

Øivind — Wed, 16 Jun 2021 08:51:18 GMT

Hi,

nrfjprog will default to the application core unless you explicitly target the network core with the argument:

--coprocessor CP_NETWORK

You also need to add a sectorerase when you program the core, and I recommend that you follow-up the command with a pinreset:

nrfjprog --program $BUILD/zephyr/zephyr.hex --sectorerase --coprocessor CP_NETWORK
nrfjprog --pinreset

"west flash" handles all of this.

When you recover a core, its flash is erased and a small program is written to it to keep the debug port open. However, when you recover the network core the flash of both cores is erased, but only the network core gets the program written to it. This means that the cores will be locked after a pin reset or power cycle, unless you recover the application core afterwards:

nrfjprog --recover --coprocessor CP_NETWORK
nrfjprog --recover

Hope this helps you resolve your issues, and let me know if you run into any other problems.