nRF5340 UART connection

[RAlexeev]

nRF52840DK devicetree describes both uart0 and uart1 explicitly in nrf52840dk_nrf52840.dts file: https://github.com/nrfconnect/sdk-zephyr/blob/v2.3.0-rc1-ncs1/boards/arm/nrf52840dk_nrf52840/nrf52840dk_nrf52840.dts#L142-L157.

Fullscreen nrf52840dk_nrf52840_dts.txt Download

&uart0 {
    compatible = "nordic,nrf-uart";
    status = "okay";
    current-speed = <115200>;
    tx-pin = <6>;
    rx-pin = <8>;
    rts-pin = <5>;
    cts-pin = <7>;
};

arduino_serial: &uart1 {
    status = "okay";
    current-speed = <115200>;
    rx-pin = <33>;
    tx-pin = <34>;
};

Firstly, I want you to locate pins for uart1: <33> and <34>. Where are they on nRF52840DK?

And nRF5340PDK devicetree describes only uart0 in nrf5340pdk_nrf5340_cpuapp_common.dts file: https://github.com/nrfconnect/sdk-zephyr/blob/v2.3.0-rc1-ncs1/boards/arm/nrf5340pdk_nrf5340/nrf5340pdk_nrf5340_cpuapp_common.dts#L96-L103.

Fullscreen nrf5340pdk_nrf5340_cpuapp_common_dts.txt Download

&uart0 {
    status = "okay";
    current-speed = <115200>;
    tx-pin = <20>;
    rx-pin = <22>;
    rts-pin = <19>;
    cts-pin = <21>;
};

As I understand, uart0 is routed to the interface MCU. Thus, how can I use another serial uart on nRF5340DK? Does it exist there at least? Should I edit a devicetree specification (nrf5340pdk_nrf5340_cpuapp_common.dts, nrf5340pdk_nrf5340_cpuapp.dts, nrf5340pdk_nrf5340_cpuappns.dts, nrf5340pdk_nrf5340_cpunet.dts) myself to define uart1, for example? And how can I define uart1 there? Can I just add something like this to the devicetree file:

Fullscreen nrf5340pdf_add_uart1_dts.txt Download

&uart1 {
    status = "okay";
    current-speed = <115200>;
    rx-pin = <ANY_PIN>;
    tx-pin = <ANY_PIN>;
};

When I built and run such an example on nRF52840DK, then uart1 initialized properly, but in the case nRF5340PDK uart1 binding failed. It's expectable since uart1 isn't defined in devicetree file. Tell me, please, should I define it there myself, as I described above, or should I do something else to use other Serial UARTs?

Fullscreen main.c Download

#include <zephyr.h>
#include <device.h>
#include <devicetree.h>
#include <sys/printk.h>
#include <drivers/uart.h>

void main(void) {
    struct device *uart = device_get_binding(DT_LABEL(DT_NODELABEL(uart1))); // uart = device_get_binding("UART_1");
    if (!uart) {
        printk("UART binding failed\n");
    } else {
        printk("UART initialized\n");
    }
}

Fullscreen prj_conf.txt Download

# Enable the UART driver
CONFIG_UART_INTERRUPT_DRIVEN=y
CONFIG_SERIAL=y
CONFIG_CONSOLE=y
CONFIG_UART_CONSOLE=y
CONFIG_UART_0_NRF_FLOW_CONTROL=y

[Susheel Nuguru]

sorry for the late response Roman,

Due to summer holidays we are a bit low staffed. I will come back to you regarding your queries tomorrow. It is a bit confusing with arduino pin number given here in nRF52 dk dts file. need to check with someone.

[Susheel Nuguru]

Hi Roman,

    rx-pin = <33>;
    tx-pin = <34>;

This most likely is the P1.01 and P1.02 (P1 has 32 pins offset from P0). This numbering scheme seems to also match the register settings 

https://infocenter.nordicsemi.com/topic/ps_nrf52840/uarte.html?cp=4_0_0_5_33_8_23#register.PSEL.TXD

 

As I understand, uart0 is routed to the interface MCU. Thus, how can I use another serial uart on nRF5340DK?

The GPIO pins (19,20,21 and 22) on nRF5340 are ALSO routed into the Segger debugger chip. You can use any GPIO pins for another instance, but you wont be able to have the segger uart CDC features of these on those pins. Apart from that you can use any other pins for the other instance of uart.

[RAlexeev]

Thanks, Susheel, for your response! And I apologise for my delay. According to your explanation, everything has properly worked for me! I tried to connect pin P1.02 as TX (34) on nRF52840 DK. And in the case of nRF5340 PDK, I assigned the same pin P1.02 (34) as TX in devicetree and it's also worked great.