RE: UART configuration and pin-definition on nRF54L15-DK

Kenneth — Mon, 08 Sep 2025 18:14:14 GMT

For those pins on the DK you also need to check the DK user guide:
https://docs.nordicsemi.com/bundle/ug_nrf54l15_dk/page/UG/nRF54L15_DK/hw_desription/connector_if.html
https://docs.nordicsemi.com/bundle/nrf-connect-board-configurator/page/index.html

Sorry I forgot that.

Kenneth

RE: UART configuration and pin-definition on nRF54L15-DK

WeBBK — Fri, 05 Sep 2025 03:37:24 GMT

Hi,

Thank you for your reply. I have followed your suggestion and added the nrfx_power_constlat_mode_request() function. For testing purposes, I have not released it yet. Unfortunately, the UART is still not working. Could you please advise if there might be any other configuration conflicts or errors that I should check?

nrf54l15dk_nrf54l15_cpuapp.overlay

&uart20 {
    status = "okay";
    current-speed = <115200>;

    /delete-property/ pinctrl-1;
    /delete-property/ pinctrl-names;

    pinctrl-0 = <&uart20_p2>;
    pinctrl-names = "default";
};

&pinctrl {
    uart20_p2: uart20_p2 {
        group1 {
            psels = <NRF_PSEL(UART_TX, 2, 2)>,
                    <NRF_PSEL(UART_RX, 2, 0)>;
        };
    };

    /delete-node/ uart20_sleep_p2;
};

prj.conf

CONFIG_SERIAL=y
CONFIG_UART_NRFX=y
CONFIG_UART_ASYNC_API=y
CONFIG_GPIO=y
CONFIG_UART_NRFX=y
CONFIG_NRFX_POWER=y

CONFIG_MAIN_STACK_SIZE=2048

CONFIG_LOG=n
CONFIG_USE_SEGGER_RTT=n
CONFIG_UART_CONSOLE=y
CONFIG_SHELL=n

main.c

#include <zephyr/kernel.h>
#include <zephyr/drivers/uart.h>
#include <zephyr/device.h>
#include <string.h>
#include <stdio.h>
#include <nrfx_power.h> //added

#define RX_TIMEOUT_US 20000
#define LINE_MAX      128

static const struct device *uart;
static char line[LINE_MAX];
static size_t linelen;

static uint8_t rxbuf1[64];
static uint8_t rxbuf2[64];
static bool buf2_in_use;

static void on_evt(const struct device *dev, struct uart_event *evt, void *ud)
{
    ARG_UNUSED(dev); ARG_UNUSED(ud);

    switch (evt->type) {
    case UART_RX_RDY: {
        const struct uart_event_rx *rx = &evt->data.rx;
        for (size_t i = rx->offset; i < rx->offset + rx->len; ++i) {
            char c = rx->buf[i];
            if (c == '\r' || c == '\n') {
                if (linelen > 0) {
                    line[linelen] = 0;
                    printk("Received: %s\n", line);
                    linelen = 0;
                }
            } else if (linelen + 1 < sizeof(line)) {
                line[linelen++] = c;
            } else {
                linelen = 0;  // overflow reset
            }
        }
        break;
    }
    case UART_RX_BUF_REQUEST:
        if (!buf2_in_use) {
            uart_rx_buf_rsp(uart, rxbuf2, sizeof(rxbuf2));
            buf2_in_use = true;
        }
        break;
    case UART_RX_BUF_RELEASED:
        if (evt->data.rx_buf.buf == rxbuf2) buf2_in_use = false;
        break;
    case UART_RX_DISABLED:
        /* continuous */
        uart_rx_enable(uart, rxbuf1, sizeof(rxbuf1), RX_TIMEOUT_US);
        break;
    default:
        break;
    }
}

int main(void)
{
    //uart = DEVICE_DT_GET(DT_CHOSEN(zephyr_console));
    uart = DEVICE_DT_GET(DT_NODELABEL(uart20));
    if (!device_is_ready(uart)) {
        return 0;
    }
    nrfx_power_constlat_mode_request(); //added

    printk("Hello World! uart20 on P2.02/P2.00 (CONSTLAT ON)\n");

    /* Async */
    uart_callback_set(uart, on_evt, NULL);
    uart_rx_enable(uart, rxbuf1, sizeof(rxbuf1), RX_TIMEOUT_US);

    while (1) {
        k_sleep(K_SECONDS(1));
    }
}

Best regards,
Webb

RE: UART configuration and pin-definition on nRF54L15-DK

Kenneth — Thu, 04 Sep 2025 14:59:38 GMT

Hi,

I think I understand the problem, and it's related to what you can find here:
https://docs.nordicsemi.com/bundle/ps_nrf54L15/page/uarte.html#d1754e919
https://docs.nordicsemi.com/bundle/ps_nrf54L15/page/chapters/pin.html#ariaid-title2
https://docs.nordicsemi.com/bundle/ps_nrf54L15/page/chapters/pin.html#d379e188
https://docs.nordicsemi.com/bundle/ps_nrf54L15/page/chapters/pin.html#ariaid-title3

Make sure to carefully read all 4 of those chapters. So I believe you need to explicit request and release constlat when using Port 2, e.g.

(#include <nrfx_power.h>) nrfx_power_constlat_mode_request(); // right before you transmit/receive something, release afterwards to reduce current when not using UART.

Edit: If you are using the DK, also see my next reply.

Kenneth