Do nRF54L15 Matter applications require external flash for OTA updates?

[xiongwei.wang]

Hello, Nordic Team!

I'm evaluating the nRF54L15 for a Matter-based product and need clarity on OTA update requirements. After reviewing the documentation and forum posts, I understand that nRF52840 definitely requires external flash for Matter OTA functionality, but I'm uncertain about the nRF54L15.

My question:

Since the nRF54L15 has larger internal memory than nRF52840, and your documentation also mentions that the nRF54L15 can compress images, I'm unsure about the firmware size threshold that necessitates using external flash for OTA updates in Matter applications.

Could you provide guidance on whether external flash is always required for nRF54L15 Matter applications, or if there's a specific firmware size threshold where it becomes necessary?

hw_requirements.html#external_flash

Regards,

wang.

[Sigurd Hellesvik]

Hi,

Could you provide guidance on whether external flash is always required for nRF54L15 Matter applications, or if there's a specific firmware size threshold where it becomes necessary?

The best generic statement I can do is what is already written in Matter hardware and memory requirements -> External flash.

So for the nRF54L15, if your application is small enough, you can use the Compressed DFU feature and then fit the application in internal flash.
Let us look at a theoretical example. From the "RAM and flash memory requirements" table:

Sample	MCUboot ROM	Application ROM	Factory data	Settings	Total ROM	Total RAM (incl. static HEAP)
Template (Release)	52	642	4	40	738	177

For DFU, we need Application ROM times 2, because it is Dual Slot DFU.

With Compressed DFU, we save ca 30%, so we get AppROM + AppROM*0.7 = 642 + 642*0.7 = 1091 ~= 1100

Then we add the rest of the rows fort Total ROM = 1100 + 52 + 4 + 40 = 1196.

The nRF54L15 has 1.5MB ROM available, so this would theoretically leave you with 300 KB of memory for your application. Of course, the above sample is for the smallest Matter sample we got, so if you want more Matter features, the calculations will change.

Also, keep in mind Known Issue: "NCSDK-20567: Partitioning limitation with MCUboot swap move", which will give you a little bit less space as well.

Does this answer what you need?

Regards,
Sigurd Hellesvik

[xiongwei.wang]

Thank you very much, Sigurd Hellesvik. Your answer was clear, detailed, and esay to understand! Thanks again!