前言

Nordic 官方 SDK 中位于 \examples\peripheral\uart\ 目录下的串口例程仅支持单串口收发，实际使用中可能需要同时使用双串口收发，通过以下方法即可实现，该方法的使用带有 EasyDMA 的 UARTE。

详细步骤

修改位于 \components\libraries\uart\ 目录下的以下3个文件（修改请先备份原文件）
（1）app_uart.h

/**
 * Copyright (c) 2013 - 2020, Nordic Semiconductor ASA
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this
 *    list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form, except as embedded into a Nordic
 *    Semiconductor ASA integrated circuit in a product or a software update for
 *    such product, must reproduce the above copyright notice, this list of
 *    conditions and the following disclaimer in the documentation and/or other
 *    materials provided with the distribution.
 *
 * 3. Neither the name of Nordic Semiconductor ASA nor the names of its
 *    contributors may be used to endorse or promote products derived from this
 *    software without specific prior written permission.
 *
 * 4. This software, with or without modification, must only be used with a
 *    Nordic Semiconductor ASA integrated circuit.
 *
 * 5. Any software provided in binary form under this license must not be reverse
 *    engineered, decompiled, modified and/or disassembled.
 *
 * THIS SOFTWARE IS PROVIDED BY NORDIC SEMICONDUCTOR ASA "AS IS" AND ANY EXPRESS
 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY, NONINFRINGEMENT, AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL NORDIC SEMICONDUCTOR ASA OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
 * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */
/**@file
 *
 * @defgroup app_uart UART module
 * @{
 * @ingroup app_common
 *
 * @brief UART module interface.
 */

#ifndef APP_UART_H__
#define APP_UART_H__

#include <stdint.h>
#include <stdbool.h>
#include "app_util_platform.h"
#include "nrf_drv_uart.h"
#include "app_fifo.h"


#ifdef __cplusplus
extern "C" {
#endif

#define  UART_PIN_DISCONNECTED 0xFFFFFFFF /**< Value indicating that no pin is connected to this UART register. */

/**@brief UART Flow Control modes for the peripheral.
 */
typedef enum
{
    APP_UART_FLOW_CONTROL_DISABLED, /**< UART Hw Flow Control is disabled. */
    APP_UART_FLOW_CONTROL_ENABLED,  /**< Standard UART Hw Flow Control is enabled. */
} app_uart_flow_control_t;

/**@brief UART communication structure holding configuration settings for the peripheral.
 */
typedef struct
{
    uint32_t                rx_pin_no;    /**< RX pin number. */
    uint32_t                tx_pin_no;    /**< TX pin number. */
    uint32_t                rts_pin_no;   /**< RTS pin number, only used if flow control is enabled. */
    uint32_t                cts_pin_no;   /**< CTS pin number, only used if flow control is enabled. */
    app_uart_flow_control_t flow_control; /**< Flow control setting, if flow control is used, the system will use low power UART mode, based on CTS signal. */
    bool                    use_parity;   /**< Even parity if TRUE, no parity if FALSE. */
    uint32_t                baud_rate;    /**< Baud rate configuration. */
} app_uart_comm_params_t;

/**@brief UART buffer for transmitting/receiving data.
 */
typedef struct
{
    uint8_t * rx_buf;      /**< Pointer to the RX buffer. */
    uint32_t  rx_buf_size; /**< Size of the RX buffer. */
    uint8_t * tx_buf;      /**< Pointer to the TX buffer. */
    uint32_t  tx_buf_size; /**< Size of the TX buffer. */
} app_uart_buffers_t;

/**@brief Enumeration which defines events used by the UART module upon data reception or error.
 *
 * @details The event type is used to indicate the type of additional information in the event
 * @ref app_uart_evt_t.
 */
typedef enum
{
    APP_UART_DATA_READY,          /**< An event indicating that UART data has been received. The data is available in the FIFO and can be fetched using @ref app_uart_get. */
    APP_UART_FIFO_ERROR,          /**< An error in the FIFO module used by the app_uart module has occured. The FIFO error code is stored in app_uart_evt_t.data.error_code field. */
    APP_UART_COMMUNICATION_ERROR, /**< An communication error has occured during reception. The error is stored in app_uart_evt_t.data.error_communication field. */
    APP_UART_TX_EMPTY,            /**< An event indicating that UART has completed transmission of all available data in the TX FIFO. */
    APP_UART_DATA,                /**< An event indicating that UART data has been received, and data is present in data field. This event is only used when no FIFO is configured. */
} app_uart_evt_type_t;

/**@brief Struct containing events from the UART module.
 *
 * @details The app_uart_evt_t is used to notify the application of asynchronous events when data
 * are received on the UART peripheral or in case an error occured during data reception.
 */
typedef struct
{
    app_uart_evt_type_t evt_type; /**< Type of event. */
    union
    {
        uint32_t error_communication; /**< Field used if evt_type is: APP_UART_COMMUNICATION_ERROR. This field contains the value in the ERRORSRC register for the UART peripheral. The UART_ERRORSRC_x defines from nrf5x_bitfields.h can be used to parse the error code. See also the \nRFXX Series Reference Manual for specification. */
        uint32_t error_code;          /**< Field used if evt_type is: NRF_ERROR_x. Additional status/error code if the error event type is APP_UART_FIFO_ERROR. This error code refer to errors defined in nrf_error.h. */
        uint8_t  value;               /**< Field used if evt_type is: NRF_ERROR_x. Additional status/error code if the error event type is APP_UART_FIFO_ERROR. This error code refer to errors defined in nrf_error.h. */
    } data;
} app_uart_evt_t;

/**@brief Function for handling app_uart event callback.
 *
 * @details Upon an event in the app_uart module this callback function will be called to notify
 *          the application about the event.
 *
 * @param[in]   p_app_uart_event Pointer to UART event.
 */
typedef void (* app_uart_event_handler_t) (app_uart_evt_t * p_app_uart_event);

struct nrf_uart_obj{
	nrf_drv_uart_t		instance;
	bool rx_done;
	bool rx_ovf;
	app_uart_event_handler_t   event_handler;
	uint8_t tx_buffer[1];
	uint8_t rx_buffer[1];
	app_fifo_t rx_fifo;    /**< RX FIFO buffer for storing data received on the UART until the application fetches them using app_uart_get(). */
	app_fifo_t tx_fifo;/**< TX FIFO buffer for storing data to be transmitted on the UART when TXD is ready. Data is put to the buffer on using app_uart_put(). */
	app_uart_comm_params_t const* comm_params;
};
typedef struct nrf_uart_obj nrf_uart_obj_t;

#define APP_UART_DEF(_name, _instance, _buf_size, _event_handler)	\
	static uint8_t	   _name##_rx_buf[_buf_size]; \
	static uint8_t	   _name##_tx_buf[_buf_size]; \
	static app_uart_buffers_t _name##_buffers = { \
		.rx_buf      = _name##_rx_buf,                     \
        .rx_buf_size = sizeof (_name##_rx_buf),            \
        .tx_buf      = _name##_tx_buf,                     \
        .tx_buf_size = sizeof (_name##_tx_buf),  \
	};  \
	nrf_uart_obj_t _name = {\
		.instance = NRF_DRV_UART_INSTANCE(_instance),\
		.rx_done = false,\
		.rx_ovf = false,\
		.event_handler = _event_handler,\
	}

/**@brief Macro for safe initialization of the UART module in a single user instance when using
 *        a FIFO together with UART.
 *
 * @param[in]   P_COMM_PARAMS   Pointer to a UART communication structure: app_uart_comm_params_t
 * @param[in]   RS485_RX_BUF_SIZE     Size of desired RX buffer, must be a power of 2 or ZERO (No FIFO).
 * @param[in]   RS485_TX_BUF_SIZE     Size of desired TX buffer, must be a power of 2 or ZERO (No FIFO).
 * @param[in]   EVT_HANDLER   Event handler function to be called when an event occurs in the
 *                              UART module.
 * @param[in]   IRQ_PRIO        IRQ priority, app_irq_priority_t, for the UART module irq handler.
 * @param[out]  ERR_CODE        The return value of the UART initialization function will be
 *                              written to this parameter.
 *
 * @note Since this macro allocates a buffer and registers the module as a GPIOTE user when flow
 *       control is enabled, it must only be called once.
 */
#define APP_UART_FIFO_INIT(P_COMM_PARAMS, RS485_RX_BUF_SIZE, RS485_TX_BUF_SIZE, EVT_HANDLER, IRQ_PRIO, ERR_CODE) \
    do                                                                                             \
    {                                                                                              \
        app_uart_buffers_t buffers;                                                                \
        static uint8_t     rx_buf[RS485_RX_BUF_SIZE];                                                    \
        static uint8_t     tx_buf[RS485_TX_BUF_SIZE];                                                    \
                                                                                                   \
        buffers.rx_buf      = rx_buf;                                                              \
        buffers.rx_buf_size = sizeof (rx_buf);                                                     \
        buffers.tx_buf      = tx_buf;                                                              \
        buffers.tx_buf_size = sizeof (tx_buf);                                                     \
        ERR_CODE = app_uart_init(P_COMM_PARAMS, &buffers, EVT_HANDLER, IRQ_PRIO);                  \
    } while (0)

/**@brief Macro for safe initialization of the UART module in a single user instance.
 *
 * @param[in]   P_COMM_PARAMS   Pointer to a UART communication structure: app_uart_comm_params_t
 * @param[in]   EVT_HANDLER   Event handler function to be called when an event occurs in the
 *                              UART module.
 * @param[in]   IRQ_PRIO        IRQ priority, app_irq_priority_t, for the UART module irq handler.
 * @param[out]  ERR_CODE        The return value of the UART initialization function will be
 *                              written to this parameter.
 *
 * @note Since this macro allocates registers the module as a GPIOTE user when flow control is
 *       enabled, it must only be called once.
 */
#define APP_UART_INIT(P_COMM_PARAMS, EVT_HANDLER, IRQ_PRIO, ERR_CODE)                              \
    do                                                                                             \
    {                                                                                              \
        ERR_CODE = app_uart_init(P_COMM_PARAMS, NULL, EVT_HANDLER, IRQ_PRIO);                      \
    } while (0)

/**@brief Function for initializing the UART module. Use this initialization when several instances of the UART
 *        module are needed.
 *
 *
 * @note Normally single initialization should be done using the APP_UART_INIT() or
 *       APP_UART_INIT_FIFO() macro depending on whether the FIFO should be used by the UART, as
 *       that will allocate the buffers needed by the UART module (including aligning the buffer
 *       correctly).

 * @param[in]     p_comm_params     Pin and communication parameters.
 * @param[in]     p_buffers         RX and TX buffers, NULL is FIFO is not used.
 * @param[in]     error_handler     Function to be called in case of an error.
 * @param[in]     irq_priority      Interrupt priority level.
 *
 * @retval      NRF_SUCCESS               If successful initialization.
 * @retval      NRF_ERROR_INVALID_LENGTH  If a provided buffer is not a power of two.
 * @retval      NRF_ERROR_NULL            If one of the provided buffers is a NULL pointer.
 *
 * The below errors are propagated by the UART module to the caller upon registration when Hardware
 * Flow Control is enabled. When Hardware Flow Control is not used, these errors cannot occur.
 * @retval      NRF_ERROR_INVALID_STATE   The GPIOTE module is not in a valid state when registering
 *                                        the UART module as a user.
 * @retval      NRF_ERROR_INVALID_PARAM   The UART module provides an invalid callback function when
 *                                        registering the UART module as a user.
 *                                        Or the value pointed to by *p_uart_uid is not a valid
 *                                        GPIOTE number.
 * @retval      NRF_ERROR_NO_MEM          GPIOTE module has reached the maximum number of users.
 */
uint32_t app_uart_init(nrf_uart_obj_t * uart_obj,
                             app_uart_buffers_t *     p_buffers,
                             app_irq_priority_t       irq_priority);

/**@brief Function for getting a byte from the UART.
 *
 * @details This function will get the next byte from the RX buffer. If the RX buffer is empty
 *          an error code will be returned and the app_uart module will generate an event upon
 *          reception of the first byte which is added to the RX buffer.
 *
 * @param[out] p_byte    Pointer to an address where next byte received on the UART will be copied.
 *
 * @retval NRF_SUCCESS          If a byte has been received and pushed to the pointer provided.
 * @retval NRF_ERROR_NOT_FOUND  If no byte is available in the RX buffer of the app_uart module.
 */
uint32_t app_uart_get(nrf_uart_obj_t * uart_obj, uint8_t * p_byte);

/**@brief Function for putting a byte on the UART.
 *
 * @details This call is non-blocking.
 *
 * @param[in] byte   Byte to be transmitted on the UART.
 *
 * @retval NRF_SUCCESS        If the byte was successfully put on the TX buffer for transmission.
 * @retval NRF_ERROR_NO_MEM   If no more space is available in the TX buffer.
 *                            NRF_ERROR_NO_MEM may occur if flow control is enabled and CTS signal
 *                            is high for a long period and the buffer fills up.
 * @retval NRF_ERROR_INTERNAL If UART driver reported error.
 */
uint32_t app_uart_put(nrf_uart_obj_t * uart_obj, uint8_t byte);

/**@brief Function for flushing the RX and TX buffers (Only valid if FIFO is used).
 *        This function does nothing if FIFO is not used.
 *
 * @retval  NRF_SUCCESS  Flushing completed (Current implementation will always succeed).
 */
uint32_t app_uart_flush(nrf_uart_obj_t * uart_obj);

/**@brief Function for closing the UART module.
 *
 * @retval  NRF_SUCCESS             If successfully closed.
 * @retval  NRF_ERROR_INVALID_PARAM If an invalid user id is provided or the user id differs from
 *                                  the current active user.
 */
uint32_t app_uart_close(nrf_uart_obj_t * uart_obj);


#ifdef __cplusplus
}
#endif

#endif //APP_UART_H__

/** @} */

（2）app_uart_fifo.c

/**
 * Copyright (c) 2015 - 2020, Nordic Semiconductor ASA
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this
 *    list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form, except as embedded into a Nordic
 *    Semiconductor ASA integrated circuit in a product or a software update for
 *    such product, must reproduce the above copyright notice, this list of
 *    conditions and the following disclaimer in the documentation and/or other
 *    materials provided with the distribution.
 *
 * 3. Neither the name of Nordic Semiconductor ASA nor the names of its
 *    contributors may be used to endorse or promote products derived from this
 *    software without specific prior written permission.
 *
 * 4. This software, with or without modification, must only be used with a
 *    Nordic Semiconductor ASA integrated circuit.
 *
 * 5. Any software provided in binary form under this license must not be reverse
 *    engineered, decompiled, modified and/or disassembled.
 *
 * THIS SOFTWARE IS PROVIDED BY NORDIC SEMICONDUCTOR ASA "AS IS" AND ANY EXPRESS
 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY, NONINFRINGEMENT, AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL NORDIC SEMICONDUCTOR ASA OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
 * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */
#include "sdk_common.h"
#if NRF_MODULE_ENABLED(APP_UART)
#include "app_uart.h"

#include "nrf_drv_uart.h"
#include "nrf_assert.h"

//static nrf_drv_uart_t app_uart_inst = NRF_DRV_UART_INSTANCE(APP_UART_DRIVER_INSTANCE);

static __INLINE uint32_t fifo_length(app_fifo_t * const fifo)
{
  uint32_t tmp = fifo->read_pos;
  return fifo->write_pos - tmp;
}

#define FIFO_LENGTH(F) fifo_length(&F)              /**< Macro to calculate length of a FIFO. */


//static app_uart_event_handler_t   m_event_handler;            /**< Event handler function. */
//static uint8_t tx_buffer[1];
//static uint8_t rx_buffer[1];
//static bool m_rx_ovf;

//static app_fifo_t                  m_rx_fifo;                               /**< RX FIFO buffer for storing data received on the UART until the application fetches them using app_uart_get(). */
//static app_fifo_t                  m_tx_fifo;                               /**< TX FIFO buffer for storing data to be transmitted on the UART when TXD is ready. Data is put to the buffer on using app_uart_put(). */

static void uart_event_handler(nrf_drv_uart_event_t * p_event, void* p_context)
{
    app_uart_evt_t app_uart_event;
    uint32_t err_code;

    nrf_uart_obj_t * uart_obj = (nrf_uart_obj_t *)p_context;

    switch (p_event->type)
    {
        case NRF_DRV_UART_EVT_RX_DONE:
            // If 0, then this is a RXTO event with no new bytes.
            if(p_event->data.rxtx.bytes == 0)
            {
               // A new start RX is needed to continue to receive data
               (void)nrf_drv_uart_rx(&uart_obj->instance, uart_obj->rx_buffer, 1);
               break;
            }

            // Write received byte to FIFO.
            err_code = app_fifo_put(&uart_obj->rx_fifo, p_event->data.rxtx.p_data[0]);
            if (err_code != NRF_SUCCESS)
            {
                app_uart_event.evt_type          = APP_UART_FIFO_ERROR;
                app_uart_event.data.error_code   = err_code;
				
				if (uart_obj->event_handler) {
					uart_obj->event_handler(&app_uart_event);
				}
            }
            // Notify that there are data available.
            else if (FIFO_LENGTH(uart_obj->rx_fifo) != 0)
            {
                app_uart_event.evt_type = APP_UART_DATA_READY;
				
				if (uart_obj->event_handler) {
					uart_obj->event_handler(&app_uart_event);
				}
            }

            // Start new RX if size in buffer.
            if (FIFO_LENGTH(uart_obj->rx_fifo) <= uart_obj->rx_fifo.buf_size_mask)
            {
                (void)nrf_drv_uart_rx(&uart_obj->instance, uart_obj->rx_buffer, 1);
            }
            else
            {
                // Overflow in RX FIFO.
                uart_obj->rx_ovf = true;
            }

            break;

        case NRF_DRV_UART_EVT_ERROR:
            app_uart_event.evt_type                 = APP_UART_COMMUNICATION_ERROR;
            app_uart_event.data.error_communication = p_event->data.error.error_mask;
            (void)nrf_drv_uart_rx(&uart_obj->instance, uart_obj->rx_buffer, 1);
		
			if (uart_obj->event_handler) {
				uart_obj->event_handler(&app_uart_event);
			}
			
            break;

        case NRF_DRV_UART_EVT_TX_DONE:
            // Get next byte from FIFO.
            if (app_fifo_get(&uart_obj->tx_fifo, uart_obj->tx_buffer) == NRF_SUCCESS)
            {
                (void)nrf_drv_uart_tx(&uart_obj->instance, uart_obj->tx_buffer, 1);
            }
            else
            {
                // Last byte from FIFO transmitted, notify the application.
                app_uart_event.evt_type = APP_UART_TX_EMPTY;
				
				if (uart_obj->event_handler) {
					uart_obj->event_handler(&app_uart_event);
				}
            }
            break;

        default:
            break;
    }
}


uint32_t app_uart_init(nrf_uart_obj_t * uart_obj,
                             app_uart_buffers_t *     p_buffers,
                             app_irq_priority_t       irq_priority)
{
    uint32_t err_code;

//    m_event_handler = event_handler;

    if (p_buffers == NULL)
    {
        return NRF_ERROR_INVALID_PARAM;
    }

    // Configure buffer RX buffer.
    err_code = app_fifo_init(&uart_obj->rx_fifo, p_buffers->rx_buf, p_buffers->rx_buf_size);
    VERIFY_SUCCESS(err_code);

    // Configure buffer TX buffer.
    err_code = app_fifo_init(&uart_obj->tx_fifo, p_buffers->tx_buf, p_buffers->tx_buf_size);
    VERIFY_SUCCESS(err_code);

	nrf_drv_uart_config_t config = NRF_DRV_UART_DEFAULT_CONFIG;
    config.baudrate = (nrf_uart_baudrate_t)uart_obj->comm_params->baud_rate;
    config.hwfc = (uart_obj->comm_params->flow_control == APP_UART_FLOW_CONTROL_DISABLED) ?
            NRF_UART_HWFC_DISABLED : NRF_UART_HWFC_ENABLED;
    config.interrupt_priority = irq_priority;
    config.parity = uart_obj->comm_params->use_parity ? NRF_UART_PARITY_INCLUDED : NRF_UART_PARITY_EXCLUDED;
    config.pselcts = uart_obj->comm_params->cts_pin_no;
    config.pselrts = uart_obj->comm_params->rts_pin_no;
    config.pselrxd = uart_obj->comm_params->rx_pin_no;
    config.pseltxd = uart_obj->comm_params->tx_pin_no;
    config.p_context = uart_obj;

    err_code = nrf_drv_uart_init(&uart_obj->instance, &config, uart_event_handler);
    VERIFY_SUCCESS(err_code);
    uart_obj->rx_ovf = false; 

    // Turn on receiver if RX pin is connected
    if (uart_obj->comm_params->rx_pin_no != UART_PIN_DISCONNECTED)
    {
        return nrf_drv_uart_rx(&uart_obj->instance, uart_obj->rx_buffer,1);
    }
    else
    {
        return NRF_SUCCESS;
    }
}


uint32_t app_uart_flush(nrf_uart_obj_t * uart_obj)
{
    uint32_t err_code;

    err_code = app_fifo_flush(&uart_obj->rx_fifo);
    VERIFY_SUCCESS(err_code);

    err_code = app_fifo_flush(&uart_obj->tx_fifo);
    VERIFY_SUCCESS(err_code);

    return NRF_SUCCESS;
}


uint32_t app_uart_get(nrf_uart_obj_t * uart_obj, uint8_t * p_byte)
{
    ASSERT(p_byte);
    bool rx_ovf = uart_obj->rx_ovf;

    ret_code_t err_code =  app_fifo_get(&uart_obj->rx_fifo, p_byte);

    // If FIFO was full new request to receive one byte was not scheduled. Must be done here.
    if (rx_ovf)
    {
        uart_obj->rx_ovf = false;
        uint32_t uart_err_code = nrf_drv_uart_rx(&uart_obj->instance, uart_obj->rx_buffer, 1);

        // RX resume should never fail.
        APP_ERROR_CHECK(uart_err_code);
    }

    return err_code;
}


uint32_t app_uart_put(nrf_uart_obj_t * uart_obj, uint8_t byte)
{
    uint32_t err_code;
    err_code = app_fifo_put(&uart_obj->tx_fifo, byte);
    if (err_code == NRF_SUCCESS)
    {
        // The new byte has been added to FIFO. It will be picked up from there
        // (in 'uart_event_handler') when all preceding bytes are transmitted.
        // But if UART is not transmitting anything at the moment, we must start
        // a new transmission here.
        if (!nrf_drv_uart_tx_in_progress(&uart_obj->instance))
        {
            // This operation should be almost always successful, since we've
            // just added a byte to FIFO, but if some bigger delay occurred
            // (some heavy interrupt handler routine has been executed) since
            // that time, FIFO might be empty already.
            if (app_fifo_get(&uart_obj->tx_fifo, uart_obj->tx_buffer) == NRF_SUCCESS)
            {
                err_code = nrf_drv_uart_tx(&uart_obj->instance, uart_obj->tx_buffer, 1);
            }
        }
    }
    return err_code;
}


uint32_t app_uart_close(nrf_uart_obj_t * uart_obj)
{
    nrf_drv_uart_uninit(&uart_obj->instance);
    return NRF_SUCCESS;
}

#endif //NRF_MODULE_ENABLED(APP_UART)

（3）retarget.c

/**
 * Copyright (c) 2014 - 2020, Nordic Semiconductor ASA
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this
 *    list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form, except as embedded into a Nordic
 *    Semiconductor ASA integrated circuit in a product or a software update for
 *    such product, must reproduce the above copyright notice, this list of
 *    conditions and the following disclaimer in the documentation and/or other
 *    materials provided with the distribution.
 *
 * 3. Neither the name of Nordic Semiconductor ASA nor the names of its
 *    contributors may be used to endorse or promote products derived from this
 *    software without specific prior written permission.
 *
 * 4. This software, with or without modification, must only be used with a
 *    Nordic Semiconductor ASA integrated circuit.
 *
 * 5. Any software provided in binary form under this license must not be reverse
 *    engineered, decompiled, modified and/or disassembled.
 *
 * THIS SOFTWARE IS PROVIDED BY NORDIC SEMICONDUCTOR ASA "AS IS" AND ANY EXPRESS
 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY, NONINFRINGEMENT, AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL NORDIC SEMICONDUCTOR ASA OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
 * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */
#include "sdk_common.h"
/** @file
 *
 * @defgroup retarget Retarget layer for stdio functions
 * @{
 * @ingroup app_common
 * @} */
#if NRF_MODULE_ENABLED(RETARGET)
#if !defined(NRF_LOG_USES_RTT) || NRF_LOG_USES_RTT != 1
#if !defined(HAS_SIMPLE_UART_RETARGET)


#include <stdio.h>
#include <stdint.h>

#include "app_uart.h"
#include "nrf_error.h"


#if defined(__CC_ARM)

// This part is taken from MDK-ARM template file and is required here to prevent
// linker from selecting libraries functions that use semihosting and failing
// because of multiple definitions of fgetc() and fputc().
// Refer to: http://www.keil.com/support/man/docs/gsac/gsac_retargetcortex.htm
// -- BEGIN --
struct __FILE { int handle; /* Add whatever you need here */ };
FILE __stdout;
FILE __stdin;
// --- END ---

extern uint32_t _app_uart_get(uint8_t * p_byte);
extern uint32_t _app_uart_put(uint8_t byte);

int fgetc(FILE * p_file)
{
    uint8_t input;
    while (_app_uart_get(&input) == NRF_ERROR_NOT_FOUND)
    {
        // No implementation needed.
    }
    return input;
}

int fputc(int ch, FILE * p_file)
{
    UNUSED_PARAMETER(p_file);

    UNUSED_VARIABLE(_app_uart_put((uint8_t)ch));
    return ch;
}

#elif defined(__GNUC__) && defined(__SES_ARM)

int __getchar(FILE * p_file)
{
    uint8_t input;
    while (app_uart_get(&input) == NRF_ERROR_NOT_FOUND)
    {
        // No implementation needed.
    }
    return input;
}

#if defined(__SES_VERSION) && (__SES_VERSION >= 34000)
int __putchar(int ch, __printf_tag_ptr tag_ptr)
{
    UNUSED_PARAMETER(tag_ptr);

    UNUSED_VARIABLE(app_uart_put((uint8_t)ch));
    return ch;
}
#else
int __putchar(int ch, FILE * p_file)
{
    UNUSED_PARAMETER(p_file);

    UNUSED_VARIABLE(app_uart_put((uint8_t)ch));
    return ch;
}
#endif

#elif defined(__GNUC__) && !defined(__SES_ARM)

int _write(int file, const char * p_char, int len)
{
    int i;

    UNUSED_PARAMETER(file);

    for (i = 0; i < len; i++)
    {
        UNUSED_VARIABLE(app_uart_put(*p_char++));
    }

    return len;
}

int _read(int file, char * p_char, int len)
{
    UNUSED_PARAMETER(file);
    while (app_uart_get((uint8_t *)p_char) == NRF_ERROR_NOT_FOUND)
    {
        // No implementation needed.
    }

    return 1;
}
#elif defined(__ICCARM__)

size_t __write(int handle, const unsigned char * buffer, size_t size)
{
    int i;
    UNUSED_PARAMETER(handle);
    for (i = 0; i < size; i++)
    {
        UNUSED_VARIABLE(app_uart_put(*buffer++));
    }
    return size;
}

size_t __read(int handle, unsigned char * buffer, size_t size)
{
    UNUSED_PARAMETER(handle);
    UNUSED_PARAMETER(size);
    while (app_uart_get((uint8_t *)buffer) == NRF_ERROR_NOT_FOUND)
    {
        // No implementation needed.
    }

    return 1;
}

long __lseek(int handle, long offset, int whence)
{
    return -1;
}
int __close(int handle)
{
    return 0;
}
int remove(const char * filename)
{
    return 0;
}

#endif

#endif // !defined(HAS_SIMPLE_UART_RETARGET)
#endif // NRF_LOG_USES_RTT != 1
#endif //NRF_MODULE_ENABLED(RETARGET)

在 sdk_config.h 配置文件中勾选启用以下配置
（1）nRF_Drivers 目录下的 NRFX_PRS_ENABLED、NRFX_UARTE_ENABLED、NRFX_UART_ENABLED 和 UART_ENABLED
（2）nRF_Libraries 目录下的 APP_FIFO_ENABLED、APP_UART_ENABLED、RETARGET_ENABLD 和 NRF_STRERROR_ENABLED
在工程中添加以下文件并设置好对应 .h 文件的路径
（1）\integration\nrfx\legacy\ 目录下的 nrf_drv_uart.c
（2）\modules\nrfx\drivers\src\prs 目录下的 nrfx_prs.c
（3）\modules\nrfx\drivers\src\ 目录下的 nrfx_uart.c、nrfx_uarte.c
（4）\components\libraries\uart\ 目录下的 app_uart_fifo.c
（5）\components\libraries\fifo\ 目录下的 app_fifo.c
（6）\components\libraries\uart\ 目录下的 retarget.c

完成以上步骤后即可开始设计你自己的初始化和收发函数，以下是我自己的设计，供大家参考
（1）platform_uart.c

#include "platform_uart.h"
#include <nrf_uart.h>
#include <nrf_log.h>

#define UART0_RECV_BUF_SIZE                 2048
#define UART1_RECV_BUF_SIZE                 2048
#define UART_SEND_FMT_BUF_SIZE              ck256

APP_UART_DEF(uart0, 0, UART0_RECV_BUF_SIZE, NULL);
APP_UART_DEF(uart1, 1, UART1_RECV_BUF_SIZE, NULL);


uint32_t _app_uart_get(uint8_t * p_byte)
{
    return app_uart_get(&uart1, p_byte);
}
uint32_t _app_uart_put(uint8_t byte)
{
    return app_uart_put(&uart1, byte);
}


void uart_init(uint8_t index, uint32_t rx_pin, uint32_t tx_pin, uint32_t baud_rate, app_irq_priority_t irq_priority)
{
	uint32_t errCode;
	nrf_uart_obj_t *nrf_uart_obj;
	static app_uart_buffers_t *buffer;
	
	if (index == 0) {
		nrf_uart_obj = &uart0;
		buffer = &uart0_buffers;
	} else if (index == 1) {
		nrf_uart_obj = &uart1;
		buffer = &uart1_buffers;
	} else {
		return;
	}

	app_uart_comm_params_t commParams;
	
	commParams.rx_pin_no = rx_pin;
	commParams.tx_pin_no = tx_pin;
	commParams.rts_pin_no = NRF_UART_PSEL_DISCONNECTED;
	commParams.cts_pin_no = NRF_UART_PSEL_DISCONNECTED;                    
	commParams.flow_control = APP_UART_FLOW_CONTROL_DISABLED;
	commParams.use_parity = false;
	commParams.baud_rate = baud_rate;
	
    nrf_uart_obj->comm_params = &commParams;
    errCode = app_uart_init(nrf_uart_obj, buffer, irq_priority);
    APP_ERROR_CHECK(errCode);
}

void uart0_init(uint32_t rx_pin, uint32_t tx_pin, uint32_t baud_rate)
{
	uart_init(0, rx_pin, tx_pin, baud_rate, APP_IRQ_PRIORITY_HIGHEST);
}

void uart1_init(uint32_t rx_pin, uint32_t tx_pin, uint32_t baud_rate)
{
	uart_init(1, rx_pin, tx_pin, baud_rate, APP_IRQ_PRIORITY_HIGHEST);
}


static void uart_send(uint8_t index, const void *send_buf, const int send_count)
{
	uint8_t *_send_buf = (uint8_t*)send_buf;
	
	nrf_uart_obj_t *nrf_uart_obj;
	
	if (index == 0) {
		nrf_uart_obj = &uart0;
	} else if (index == 1) {
		nrf_uart_obj = &uart1;
	} else {
		return;
	}
	
	for (int i = 0; i < send_count; i++) {
		while (app_uart_put(nrf_uart_obj, _send_buf[i]) != NRF_SUCCESS);
	}
}


void uart0_send(const void *send_buf, const int send_count)
{
	uart_send(0, send_buf, send_count);
}

void uart1_send(const void *send_buf, const int send_count)
{
	uart_send(1, send_buf, send_count);
}


static int uart_receive(uint8_t index, void *receive_buf, const int receive_count) 
{	
	uint8_t *_receive_buf = (uint8_t*)receive_buf;
	
	nrf_uart_obj_t *nrf_uart_obj;
	
	if (index == 0) {
		nrf_uart_obj = &uart0;
	} else if (index == 1) {
		nrf_uart_obj = &uart1;
	} else {
		return -1;
	}
	
	int i, receive_count_real;

	for(i = 0, receive_count_real = 0; i < receive_count; i++) {
		if(app_uart_get(nrf_uart_obj, &_receive_buf[i]) != NRF_SUCCESS) {
			break;
		} else {
			receive_count_real++;
		}
	}
	
	return receive_count_real;
}

int uart0_receive(void *receive_buf, const int receive_count)
{
	return uart_receive(0, receive_buf, receive_count);
}

int uart1_receive(void *receive_buf, const int receive_count)
{
	return uart_receive(1, receive_buf, receive_count);
}

（2）platform_uart.h

#ifndef __PLATFORM_UART_H__
#define __PLATFORM_UART_H__
#include <app_uart.h>
#include <stdint.h>

void uart_init(uint8_t index, uint32_t rx_pin, uint32_t tx_pin, uint32_t baud_rate, app_irq_priority_t irq_priority);

void uart0_init(uint32_t rx_pin, uint32_t tx_pin, uint32_t baud_rate);
void uart1_init(uint32_t rx_pin, uint32_t tx_pin, uint32_t baud_rate);

void uart0_send(const void *send_buf, const int send_count);
void uart1_send(const void *send_buf, const int send_count);
	
int uart0_receive(void *receive_buf, const int receive_count);
int uart1_receive(void *receive_buf, const int receive_count);

#endif

参考：https://blog.csdn.net/qq_36347513/article/details/111319840

nRF5 SDK 如何同时使用双串口进行数据收发

前言

详细步骤