UARTE21 and SPIM20 on P2 issues

[Evluma]

Hello and thank you for your time,

We have created a board using the nRF54l15 and have used P2.07 & P2.08 for UARTE21 and P2.00 to P2.05 for SPIM20.

UARTE21 and SPIM20 do not work on P2 thus far.

I have used UARTE00 and SPIM00, separately due to resource sharing issues, and both work with their separate devices, notably altering the current-speed to 1/8 normal.

The pin selection on P2 is dedicated and this is accounted for and shown to be correct on our board due to the UARTE00 and SPIM00 working with the devices.

The data sheets for the nRF54l15 "SEEM" to indicate that UART20/21 and SPIM20/21 can be used on P2, cross power domain, but I have not been able to get this to work properly and have found no examples showing this working.

So the questions are:

- do UART20/21 and SPIM20/21 work on P2 as indicated in the data sheet?

- are the rates normal for UART20/21 and SPIM20/21 on P2 or are they also multiplied by 8?

- if they do work, is their a working example for the nRF54l15DK?

- alternately, is there resource sharing such that UARTE00 and SPIM00 can be switched between each other at runtime?

During my search for answers I found one promising reference for this:

- Case ID: 342324

[Jørgen Holmefjord]

Hi,

I have used UARTE00 and SPIM00, separately due to resource sharing issues, and both work with their separate devices, notably altering the current-speed to 1/8 normal.

There is a pull request to fix this (at least for UARTE00): https://github.com/zephyrproject-rtos/zephyr/pull/82112/

- do UART20/21 and SPIM20/21 work on P2 as indicated in the data sheet?

Yes, but you can only use the dedicated pins specified in pin assignment table (e.g. P2.07 for UARTE21 RX, P2.08 for UARTE21 TX). Also note that you need to enable Constant Latency mode when using pins on P2. This can be done as mentioned in the ticket you linked, or to force it on at all times, you can set CONFIG_SOC_NRF_FORCE_CONSTLAT=y in your prj.conf file.

- are the rates normal for UART20/21 and SPIM20/21 on P2 or are they also multiplied by 8?

The rates are normal. The clock source is related to the instance itself and not which pins you have connected the peripheral to.

- if they do work, is their a working example for the nRF54l15DK?

Attaching a modified version of the hello_world sample where UARTE21 is configured to use P2.08/P2.07:

hello_world_nrf54l15_uart21_p2_ncs290.zip

- alternately, is there resource sharing such that UARTE00 and SPIM00 can be switched between each other at runtime?

Not a specific example for nRF54L15, but you can reference this sample that shows how to switch during runtime. Note that this is using NRFX and not the Zephyr drivers.

Best regards,
Jørgen