Rtthread学习笔记（五）串口设备使用示例--DMA 接收及轮询发送

一、DMA 接收及轮询发送

当串口接收到一批数据后会调用接收回调函数，接收回调函数会把此时缓冲区的数据大小通过消息队列发送给等待的数据处理线程。线程获取到消息后被**，并读取数据。一般情况下 DMA 接收模式会结合 DMA 接收完成中断和串口空闲中断完成数据接收。

运行序列图如下图所示：

二、步骤

1.注册uart2 board.h

2.开启DMA stm32f1xx_hal_conf.h

3.开启uart2

app_uart2.c

/*
 * Copyright (c) 2006-2020, RT-Thread Development Team
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * Change Logs:
 * Date           Author       Notes
 * 2020-04-14     David       the first version
 */

#include "app_uart2.h"

#define SAMPLE_UART_NAME       "uart2"

/* 串口接收消息结构*/
struct rx_msg
{
    rt_device_t dev;
    rt_size_t size;
};
/* 串口设备句柄 */
static rt_device_t serial;
/* 消息队列控制块 */
static struct rt_messagequeue rx_mq;

/* 接收数据回调函数 */
static rt_err_t uart_input(rt_device_t dev, rt_size_t size)
{
    struct rx_msg msg;
    rt_err_t result;
    msg.dev = dev;
    msg.size = size;

    result = rt_mq_send(&rx_mq, &msg, sizeof(msg));
    if ( result == -RT_EFULL)
    {
        /* 消息队列满 */
        rt_kprintf("message queue full！\n");
    }
    return result;
}


static void serial_thread_entry(void *parameter)
{
    struct rx_msg msg;
        rt_err_t result;
        rt_uint32_t rx_length;
        static char rx_buffer[RT_SERIAL_RB_BUFSZ + 1];

        while (1)
        {
            rt_memset(&msg, 0, sizeof(msg));
            /* 从消息队列中读取消息*/
            result = rt_mq_recv(&rx_mq, &msg, sizeof(msg), RT_WAITING_FOREVER);
            if (result == RT_EOK)
            {
                /* 从串口读取数据*/
                rx_length = rt_device_read(msg.dev, 0, rx_buffer, msg.size);
                rx_buffer[rx_length] = '\0';
                /* 通过串口设备 serial 输出读取到的消息 */
                rt_device_write(serial, 0, rx_buffer, rx_length);
                /* 打印数据 */
                rt_kprintf("%s\n",rx_buffer);
            }
        }
}

void CreatUart2TestEntry(void)
{
    static char msg_pool[256];
    char str[] = "hello RT-Thread!666\r\n";
    /* 查找串口设备 */
       serial = rt_device_find(SAMPLE_UART_NAME);
       if (!serial)
       {
           rt_kprintf("find %s failed!\n", SAMPLE_UART_NAME);
       }

       /* 初始化消息队列 */
       rt_mq_init(&rx_mq, "rx_mq",
                  msg_pool,                 /* 存放消息的缓冲区 */
                  sizeof(struct rx_msg),    /* 一条消息的最大长度 */
                  sizeof(msg_pool),         /* 存放消息的缓冲区大小 */
                  RT_IPC_FLAG_FIFO);        /* 如果有多个线程等待，按照先来先得到的方法分配消息 */

       /* 以 DMA 接收及轮询发送方式打开串口设备 */
       rt_device_open(serial, RT_DEVICE_FLAG_DMA_RX);
       /* 设置接收回调函数 */
       rt_device_set_rx_indicate(serial, uart_input);
       /* 发送字符串 */
       rt_device_write(serial, 0, str, (sizeof(str) - 1));

       /* 创建 serial 线程 */
       rt_thread_t thread = rt_thread_create("serial", serial_thread_entry, RT_NULL, 1024, 25, 10);
       /* 创建成功则启动线程 */
       if (thread != RT_NULL)
       {
           rt_thread_startup(thread);
       }
       else
       {
           rt_kprintf("Create %s Entry failed!\n", SAMPLE_UART_NAME);
       }

}

app_uart2.h

/*
 * Copyright (c) 2006-2020, RT-Thread Development Team
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * Change Logs:
 * Date           Author       Notes
 * 2020-04-14     CRJ       the first version
 */
#ifndef APPLICATIONS_APP_UART2_H_
#define APPLICATIONS_APP_UART2_H_

#include <rtthread.h>

extern void CreatUart2TestEntry(void);//放在mian中


#endif /* APPLICATIONS_APP_UART2_H_ */

三、验证