nRF Connect SDK: SPI communication is not working on nRF52840 dev kit

[Kalyan Agepati]

Hi nRF support team,

By using the nRF Connect SDK, I am trying to implement an SPI communication with the display module from my nRF52840 dev kit and nRF52840 as a master.
I have tried below test code. But I m not receiving invalid data on MOSI pin and also not receiving a proper clock signal.

Can you please share the working sample code of SPI as a master of nRFconnect SDK?

This is my .overlay configuration:
&spi3 {
    status = "okay";
    cs-gpios = <&gpio0 12 0>;

    stxxxx@0 {
        compatible = "sitronix,stxxxx";
        label = "STxxxx";
        spi-max-frequency = <2000000>;
        reg = <0>;
        };
};

nRFsdk Pin configuration:
CS  <-> P0.12
CLK <-> P1.15
MISO <-> P1.14
MOSI <-> P1.13

Test Code:
struct device *spi_dev;
struct spi_cs_control spi_cs;
        
const struct spi_config spi_cfg = {
    .operation = SPI_OP_MODE_MASTER | SPI_WORD_SET(8) | SPI_TRANSFER_MSB |
             SPI_MODE_CPOL | SPI_MODE_CPHA,
    .frequency = 2000000,
    //.slave = 0,
};

static void spi_init(void)
{

    spi_cs.gpio_dev = device_get_binding("STxxxx");
           spi_cs.gpio_pin = DT_INST_SPI_DEV_CS_GPIOS_PIN(0);
    spi_cs.delay = 0;
        spi_cs.gpio_dt_flags = GPIO_ACTIVE_LOW;
       
    //spi_cfg.cs = &spi_cs;

        printk("SPI Initiating...");
    spi_dev = device_get_binding("STxxxx");
    if (spi_dev == NULL) {
        printk("\n******* Display device not found.  Aborting test. *******\n");
        return;
    }
}

void spi_send(struct device *spi_dev)
{
    int err;
    static uint8_t tx_buffer[1];
    static uint8_t rx_buffer[1];

    const struct spi_buf tx_buf = {
        .buf = tx_buffer,
        .len = sizeof(tx_buffer)
    };
    const struct spi_buf_set tx = {
        .buffers = &tx_buf,
        .count = 1
    };

    struct spi_buf rx_buf = {
        .buf = rx_buffer,
        .len = sizeof(rx_buffer),
    };
    const struct spi_buf_set rx = {
        .buffers = &rx_buf,
        .count = 1
    };
    err = spi_transceive(spi_dev, &spi_cfg, &tx, &rx);
    if (err) {
        printk("SPI write error: %d\n", err);
    } else {
        /* Connect MISO to MOSI for loopback */
        printk("MISO TX sent: %x\n", tx_buffer[0]);
        printk("MOSI RX recv: %x\n", rx_buffer[0]);
    }    
            
}

void main(void)
{  
        printk("\n**** main() start... ****\n");
        //Initlize the SPI module
        spi_init();
    
        while (1)
    {
              spi_send(spi_dev);
              k_sleep(K_SECONDS(2));
    }
}

Thanks in advance.
Regards,
Kalyan