Connect cross power-domain to UART00 on P2 of nRF54L15 DK

[Archiet]

Hi there!

May I know how to have UART00 on P2 like what is shown below as I wanted to have higher speed.

Is it the same as other UART assignments on P0 and P1?

Thanks!

[Edvin]

Hello,

Please see the cross power-domain section of the pin assignment documentation for the nRF54L15.

What pins specifically are you trying to use? Have you used a logic analyzer to see if any of the pins are doing anything? 

Best regards,

Edvin

[Archiet]

Hi there!

I have read the link you shared before. I know it mentions dedicated pins in pin assignment table but I still want to know if I can use any P2 pins for UARTE00. For example, is it possible to use P2.06 to P2.09 for UART with flow control? I understand UART is not mentioned under description and dedicated function of P2.06 but I wanted to know if I can use it by configuration of certain registers.

[Edvin]

Thank you for the update. Yes. It will be part of the 3.0.0 release, and therefore also part of the preview/release candidates.

BR,
Edvin

[papatel]

I'm on 3.1.1 and I can't get uart00 working with P2.07 and P2.08 for TX/RX. Everything compiles just fine but TX line doesn't toggle when I write out to UART and nothing can be received either.  Did something break in the latest SDK for P2 + uart?

[Edvin]

Make sure P2.07 is RX and P2.08 is TX. 

Source: https://docs.nordicsemi.com/bundle/ps_nrf54L15/page/chapters/pin.html#ariaid-title4

BR,

Edvin

[papatel]

Yes, this was our mistake and every LLM we tried also made the same mistake in assuming that UART pin assignments (TX vs RX) were not restricted, only the peripheral itself within P2.  This was an unexpected limitation and a HUGE step backward in terms of ease of integration.

This severe limitation is documented but Nordic should probably make that more clear as anyone familiar with the NRF52 series would never make the assumption that pin assignments for UART are completely restricted for any port.

Nordic engineers also missed this in our private schematic review.

Lastly the build environment doesn't complain at all when we selected incompatible TX/RX pins on port 2 or assigned the wrong peripheral.  Compiles just fine and fails completely silently during testing no matter what logs/traces/debugging you turn on.  That should be fixed in parallel with more clarity on the documentation.

[Edvin]

I am sorry that this wasn't picked up earlier.

Yes, there are some more limitations on the pin selection, compared to the nRF52 and nRF53 series. Also, it is unfortunate that the build system doesn't pick up these kinds of mistakes. We have reported this internally. 

Best regards,

Edvin