nRF5340 NET Core PCD Update Fails in NCS v2.6.3+ (SoftDevice Lib Change)

RE: nRF5340 NET Core PCD Update Fails in NCS v2.6.3+ (SoftDevice Lib Change)

Gabriele — Tue, 27 Jan 2026 07:19:33 GMT

Hi Einar,

By continuing debugging, we understood the probable cause of the error was an incorrect buffer flushing procedure that prevented a complete flush of buffered writes.
The flush was only performed when the stream buffer, which we configured to 512 B, was full.
So, in reality, the problem was occurring even before, except that the FW generated with the old SDKs had a size closer to a multiple of 512:
- with SDK v2.6.2, the size is 177,704 B, or 347 * 512 + 40
- with SDK v2.6.3, the size is 177,944 B, or 347 * 512 + 280
So, with the old SDK, 40 B remained in RAM that wasn't written to the flash, but these were probably padding and/or alignment bytes, since everything worked correctly. With the new SDK, however, 280 B remain in RAM, and this truncation is significant.
Therefore this case can be considered solved. Thank you.

RE: nRF5340 NET Core PCD Update Fails in NCS v2.6.3+ (SoftDevice Lib Change)

Einar Thorsrud — Tue, 20 Jan 2026 09:02:55 GMT

Hi,

I see. Can you debug a bit in the network core bootloader (netboot/B0n) to see more of what causes the error? I would start looking at where pcd_fw_copy_invalidate() is called in nrf/samples/nrf5340/netboot/src/main.c, and backtracking from there it should be possible to see more precisely what failed.

RE: nRF5340 NET Core PCD Update Fails in NCS v2.6.3+ (SoftDevice Lib Change)

Gabriele — Mon, 19 Jan 2026 14:32:12 GMT

Hi Einar,

The error is specifically within the network_core_pcd_cmdset() function (defined in nrf/subsys/pcd/src/pcd.c).

On the first iteration within the do-while loop (the only one in that function), when the assignment is executed

command_status = pcd_fw_copy_status_get();

PCD_STATUS_FAILED is immediately returned, and execution terminates after printing the error message mentioned above ("Network core update failed").

Regarding the size of pcd_sram, it has remained at 8KB, as it was previously.

Our netcore FW update is 177944 B in size with the new SKD (with SDK v2.6.2 it was 177704 B), but we have 256 KB for the CPUNET flash_primary, so it doesn't appear to be a memory saturation issue.

RE: nRF5340 NET Core PCD Update Fails in NCS v2.6.3+ (SoftDevice Lib Change)

Einar Thorsrud — Mon, 19 Jan 2026 13:39:20 GMT

Hi,

I have not been able to find any known issues that match this description, nor any similar reports. Can you share you rmemory paritioning? What is the size of pcd_sram in particular? Have you learned anything more from debugging (particularily if you have debugged in nrf/subsys/pcd/src/pcd.c and see some error return codes)?