10 串口2 DMA收发 485 波特率115200时正常，到了230400就不正常了

发布于 2021-06-21 03:28:22 浏览：2160 订阅该版

开发环境：STM32CubeMX
RTT:4.03
芯片:STM32F407

```c
#include "uart2.h"

#include <rtthread.h>
#include <board.h>
#include <rtdevice.h>

#define    uart2_tempsum   120            //串口缓冲数据个数
uint8_t    uart2_rx[uart2_tempsum]={0};   //串口发送缓冲个数
uint8_t    uart2_tx[uart2_tempsum]={0};   //串口接收缓冲个数
uint8_t    uart2_temp[uart2_tempsum]={0}; //串口临时缓冲
u16        uart2_ReceiveLen=0;            //串口接收的数据个数
u16        uart2_SendLen=0;               //串口发送的数据个数
struct     serial_configure config2 = RT_SERIAL_CONFIG_DEFAULT;  /* 初始化配置参数 */

#define    UART2_NAME       "uart2"       // 串口设备名称
static     rt_device_t uart2_serial;      //串口设备句柄
static     struct rt_messagequeue rx_mq2;  //消息队列控制块

/* 串口接收消息结构*/
struct rx_msg
{
    rt_device_t dev;
    rt_size_t size;
};

/* 接收数据回调函数 */
static rt_err_t uart2_Receive(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_mq2, &msg, sizeof(msg));
    if ( result == -RT_EFULL)
    {
        /* 消息队列满 */
        rt_kprintf("message queue full！\n");
    }
    return result;
}
/* 接收数据回调函数 */
static rt_err_t uart2_Send(rt_device_t dev, rt_size_t size)
{
    EN2=0;
    return 0;
}

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];

rt_thread_mdelay(3000);

uart2_serial = rt_device_find(UART2_NAME);  //查找串口设备
    if (!uart2_serial)
    {
        rt_kprintf("find %s failed!\n", UART2_NAME);
        return RT_ERROR;
    }

/* 初始化消息队列 */
    rt_mq_init(&rx_mq2, "rx_mq2",
               uart2_temp,                 /* 存放消息的缓冲区 */
               sizeof(struct rx_msg),    /* 一条消息的最大长度 */
               uart2_tempsum,         /* 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 */

rt_device_control(uart2_serial, RT_DEVICE_CTRL_CONFIG, &config2);
    /* 以 DMA 接收及轮询发送方式打开串口设备 */
    rt_device_open(uart2_serial, RT_DEVICE_FLAG_DMA_RX|RT_DEVICE_FLAG_DMA_TX);
    /* 设置接收回调函数 */
    rt_device_set_rx_indicate(uart2_serial, uart2_Receive);
    /* 设置发送回调函数 */
    rt_device_set_tx_complete(uart2_serial, uart2_Send);
    /* 发送字符串 */
    //rt_device_write(uart2_serial, 0, str, (sizeof(str) - 1));
    while (1)
    {
        rt_memset(&msg, 0, sizeof(msg));
        /* 从消息队列中读取消息*/
        result = rt_mq_recv(&rx_mq2, &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 uart2_serial 输出读取到的消息 */
            EN2=1;
            rt_device_write(uart2_serial, 0, rx_buffer, rx_length);
            //EN2=0;
            /* 打印数据 */
            rt_kprintf("%d\n",rx_length);
        }
    }
}

//baud_rate : 修改波特率
//data_bits : 数据位
//stop_bits : 停止位
//parity    : 校验位
int uart2_dma_start(u16 baud_rate,u16 data_bits,u16 stop_bits,u16 parity)
{
    int res;

/* step2：修改串口配置参数 */
    config2.baud_rate = baud_rate;        //修改波特率为 9600
    config2.data_bits = data_bits;           //数据位 8
    config2.stop_bits = stop_bits;           //停止位 1
    config2.bufsz     = 128;                   //修改缓冲区 buff size 为 128
    config2.parity    = parity;           //无奇偶校验位

/* 创建 uart2_serial 线程 */
    rt_thread_t thread = rt_thread_create("uart2_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("uart2_dma_start failed\n");
        res = -1;
    }

return res;
}
```

![image.png](https://oss-club.rt-thread.org/uploads/20210621/fd2dcb6e50379e5f90474fa258a45f65.png.webp)

![image.png](https://oss-club.rt-thread.org/uploads/20210621/92e96c347ea1ac71842a2d6bc501ec14.png.webp)