Issue of UART20 can't work when setting P2.02 as TXD and P2.00 as RXD both on the custom board and DK

[Tom.Fu]

Hi Support Team

UART20 of nRF54L15 can't work when setting P2.02 as TXD and P2.00 as RXD when I test the central_uart sample of NCS V2.9.1. I find that the SPI00 has used the P2.02, but UART20 still can't work after I disable the SPI00 in the overlay file. Any other configration is need for the UART20 work with P2.02 and P2.00? Many thanks.

[Kenneth]

Hello,

For the DK you should check the following information:
https://docs.nordicsemi.com/bundle/ug_nrf54l15_dk/page/UG/nRF54L15_DK/hw_desription/solder_bridge.html 

However there is a few things you should be aware of when using P2 pins for UARTE20/21, this is missing from the current datasheet (v0.8), but will be fixed in future releases (v0.9 and later):

Peripherals must use pins in their own domain. However, some P2 pins can be used for select serial interfaces in the peripheral (/)domain if Constant Latency sub power mode is enabled.

UARTE20/21 Can use any pin on P1. Can connect across power domains to dedicated pins on P2 if in Constant Latency mode.

Selected pins of P2 can be used for some serial interfaces in the peripheral domain — SPIM, SPIS, and UARTE, if Constant Latency sub power mode is enabled.

See section 5.1.1 "Sub-power modes" in the datasheet on how to enabled constant latency.

Kenneth

[Tom.Fu]

Hello Kenneth

Ok, we try as your suggestion like the screenshot below to enable the Constant Latency sub power mode, but it still can't work. The attachment is my code. Could you help check where I made mistake? Many thanks.

uart_int_p2.7z

[Kenneth]

Did you also follow:

For the DK you should check the following information:
https://docs.nordicsemi.com/bundle/ug_nrf54l15_dk/page/UG/nRF54L15_DK/hw_desription/solder_bridge.html

SB13	Closed	Cut to disconnect the SPI external memory from P2.02
SB16	Closed	Cut to disconnect the SPI external memory from P2.00
SB17	Open	Short to enable P2.00 as a normal GPIO
SB19	Open	Short to enable P2.02 as a normal GPIO

Kenneth