How to config device tree to use UART00 or UART21 for TXD output to P2.08

RE: How to config device tree to use UART00 or UART21 for TXD output to P2.08

Menon — Thu, 29 Jan 2026 10:14:06 GMT

Hello,

No worries, I’ll close it from my side.Kind Regards,

Abhijith

RE: How to config device tree to use UART00 or UART21 for TXD output to P2.08

John So — Thu, 29 Jan 2026 09:38:11 GMT

Hi,

It's strange that I cannot find the 'close ticket' button on this page. Can you close it for me?

Best Regards

John

RE: How to config device tree to use UART00 or UART21 for TXD output to P2.08

Menon — Wed, 28 Jan 2026 09:09:10 GMT

Hello,

Please don’t hesitate to create a new ticket if you come across any new issues. Also, feel free to close this ticket at your convenience.

Kind regards,
Abhijith

RE: How to config device tree to use UART00 or UART21 for TXD output to P2.08

John So — Wed, 28 Jan 2026 05:31:55 GMT

Noted, thanks!!

RE: How to config device tree to use UART00 or UART21 for TXD output to P2.08

Menon — Mon, 26 Jan 2026 11:00:27 GMT

Hello,

This is because P2 is in the MCU power domain, while UARTE20/21 are peripherals in the PERI domain. Using P2 pins with UARTE2x is only supported as a cross power domain connection, and you also need to enable constant latency mode.

Please refer to the Power Domains and GPIO section in the documentation. You can also check this older DevZone ticket, which explains the same issue.

Kind Regards,

Abhijith

RE: How to config device tree to use UART00 or UART21 for TXD output to P2.08

John So — Mon, 26 Jan 2026 07:43:54 GMT

Hi Abhijith,

The build issue is fixed. The root cause is: I have not set status = "okay" for the UART module (UART00 or 21).

However, it finds that for P2.07/P2.08, I can only use UART00 but not UART21. If I use UART21 on P2.08, it can build the firmware but the firmware cannot run.

On the product spec, it states that either UART00 or UART21 can be used on those pins.

Would you help to find out why UART21 cannot be used on P2.07/P2.08?

Is there any setting in the nRF54L15DK board restrict the use of UART21 on P2.08?

Best Regards

John

RE: How to config device tree to use UART00 or UART21 for TXD output to P2.08

Menon — Fri, 23 Jan 2026 13:52:41 GMT

hello,

Could you please share the build log showing the exact error message you’re getting, and also check the generated device tree (build/app/zephyr/zephyr.dts) after the build? It would be helpful to see whether the UART you’re trying to use (uart00 or uart21) is actually present and enabled there, along with its pinctrl configuration, as this should clarify whether the issue is coming from the board configuration or the DTS setup.

Kind Regards,

Abhijith