How program serialnumber on nRF54L15 in factory setup

RE: How program serialnumber on nRF54L15 in factory setup

Hung Bui — Thu, 30 Oct 2025 07:50:22 GMT

Hi Emil,
Thanks for your feedback. I agree that it is a bit confusing. But if you have a look at section 4.2.9 UICR you can find that it's mentioned that the OTP is an "emulated one-time programmable (OTP)". So it's not real OTP but emulated meaning it can be erased when doing an "erase all" operation.

RE: How program serialnumber on nRF54L15 in factory setup

Emil Lenngren — Tue, 28 Oct 2025 14:47:08 GMT

I have a request that you make it clear in the documentation that even though it's called OTP, it can actually be rewritten if you perform an erase all operation. The text "it is possible only once after an erase all operation" doesn't logically imply that an erase all would also reset OTP. Your AI bot believed that OTP actually was one-time-programmable and that erase all wouldn't reset it.

RE: How program serialnumber on nRF54L15 in factory setup

Hung Bui — Tue, 28 Oct 2025 14:34:31 GMT

Hi Tommy,
Thanks for your patience, regarding the OTP reserved for customer use, there is now a PR:
https://github.com/nrfconnect/sdk-nrf/pull/24686

You can find the draft documentation here: https://ncsdoc.z6.web.core.windows.net/PR-24686/nrf/app_dev/device_guides/nrf54l/otp_map_nrf54l.html

There are 32x4 bytes available at the bottom of the OTP area.

RE: How program serialnumber on nRF54L15 in factory setup

Hung Bui — Thu, 06 Mar 2025 11:51:03 GMT

Hi Tommy,
I has reported the request internally. The team is looking at it. But I am not sure if we will have a solution available in your time frame.

From my point of view, if you decide to use the OTP for the purpose, the biggest risk is when we start using it in the future for other modules in NCS and you need to do DFU update there can be a conflict.
When you do DFU update to the newer firmware and there will be a chance that the firmware will try to write to the OTP registers that you already written.

However the chance is quite small, from my point of view, as you only use 4 out of 320 registers. And there still a solution that you can modify the firwmare to avoid using the same area before you do DFU update.

I would suggest if we don't come up with a office solution, you can just use the OTP (if using the flash is proven to be too much work). My suggestion is to choose the registers at the bottom of the OTP area.
This is just my personal suggestion, as the proper way of doing this for now is still using flash. I can't guarantee it will not cause any problem in the future.

RE: How program serialnumber on nRF54L15 in factory setup

Tommy F Kristensen — Wed, 05 Mar 2025 11:03:46 GMT

Hi Hung Bui

Thanks for you answer.

We are planning to go into mass a month from now, so we would really appriciate that this could be prioritized.

We are using the serial numbers as unique identifiers of our products in the system, so it is quite important that we have a solution.

We only need 4 32 bit registers, to store the data in, so if you have some of the OTP registers that could be reserved to the costumer it would be great

Best Regards

Tommy F Kristensen

RE: How program serialnumber on nRF54L15 in factory setup

Hung Bui — Wed, 05 Mar 2025 09:13:34 GMT

Hi Tommy,
I'm aware of the OTP register in the UICR. But the reason that the name changed from CUSTOMER[] to OTP[] is that the OS/drivers will also use some of the registers to store data. We are working on defining where the safe location for custom user data is.

RE: How program serialnumber on nRF54L15 in factory setup

Tommy F Kristensen — Tue, 04 Mar 2025 14:28:30 GMT

Hi Hung Bui

Im loooking into if it is possbile to store the serial number and other factory specific data in the UICR ->OTP area.

It has 320 adresses reserved for OTP.

I will use the nrfutil to set the serial numner

nrfutil device x-write --address 0x00FFD504 --value 0x0100FF19

nrfjprog --program serial.hex // that flashes the hexfile containing the serial number etc for the device

Then read it back in the code like this

Best Regards

Tommy F Kristensen

RE: How program serialnumber on nRF54L15 in factory setup

Hung Bui — Tue, 04 Mar 2025 13:53:57 GMT

Hi Tommy,

This is something we are looking at to find a solution.

Until we find a better solution you will need to use the flash area to store the serial number. You can either store it using NVS or Settings, or other nonvolatile module to store the serial number.
It can be a challenge if you also use the module to store other data because NVS or settings will move the data around for garbage collection, wear leveling.
If you configure a partition only for storing the manufacturing data separated from any other flash activity in the application and don't do any other activity on the partition,I think it should be safe. And you should be able to use the programmer to write a hex file directly to the partition's address.