串口收发不定长数据存在乱码和丢包

发布于 2021-06-09 15:33:08 浏览：1384 订阅该版

官方的串口demo3，串口收发不定长数据。源码不修改，只是更改了串口端号。串口1收发数据，串口2进行log观察。发现存在丢包、乱码现象。
```
/*
 * Copyright (c) 2006-2021, RT-Thread Development Team
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * Change Logs:
 * Date           Author       Notes
 * 2021-06-02     MF       the first version
 */
#include <rtthread.h>
#include <board.h>

#define DBG_TAG "main"
#define DBG_LVL DBG_LOG
#include <rtdbg.h>

#define SAMPLE_UART_NAME                 "uart1"
#define DATA_CMD_END                     '\r'       /* 结束位设置为 \r，即回车符 */
#define ONE_DATA_MAXLEN                  20         /* 不定长数据的最大长度 */

/* 用于接收消息的信号量 */
static struct rt_semaphore rx_sem;
static rt_device_t serial;

/* 接收数据回调函数 */
static rt_err_t uart_rx_ind(rt_device_t dev, rt_size_t size)
{
    /* 串口接收到数据后产生中断，调用此回调函数，然后发送接收信号量 */
    if (size > 0)
    {
        rt_sem_release(&rx_sem);
    }
    return RT_EOK;
}

static char uart_sample_get_char(void)
{
    char ch;

while (rt_device_read(serial, 0, &ch, 1) == 0)
    {
        rt_sem_control(&rx_sem, RT_IPC_CMD_RESET, RT_NULL);
        rt_sem_take(&rx_sem, RT_WAITING_FOREVER);
    }
    return ch;
}

/* 数据解析线程 */
static void data_parsing(void)
{
    char ch;
    char data[ONE_DATA_MAXLEN];
    static char i = 0;

while (1)
    {
        ch = uart_sample_get_char();
        rt_device_write(serial, 0, &ch, 1);
        if(ch == DATA_CMD_END)
        {
            data[i++] = '\0';
            rt_kprintf("data=%s\r\n",data);
            i = 0;
            continue;
        }
        i = (i >= ONE_DATA_MAXLEN-1) ? ONE_DATA_MAXLEN-1 : i;
        data[i++] = ch;
    }
}

static int u(int argc, char *argv[])
{
    rt_err_t ret = RT_EOK;
    char uart_name[RT_NAME_MAX];
    char str[] = "hello RT-Thread!\r\n";

if (argc == 2)
    {
        rt_strncpy(uart_name, argv[1], RT_NAME_MAX);
    }
    else
    {
        rt_strncpy(uart_name, SAMPLE_UART_NAME, RT_NAME_MAX);
    }

/* 查找系统中的串口设备 */
    serial = rt_device_find(uart_name);
    if (!serial)
    {
        rt_kprintf("find %s failed!\n", uart_name);
        return RT_ERROR;
    }

/* 初始化信号量 */
    rt_sem_init(&rx_sem, "rx_sem", 0, RT_IPC_FLAG_FIFO);
    /* 以中断接收及轮询发送模式打开串口设备 */
    rt_device_open(serial, RT_DEVICE_FLAG_INT_RX);
    /* 设置接收回调函数 */
    rt_device_set_rx_indicate(serial, uart_rx_ind);
    /* 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", (void (*)(void *parameter))data_parsing, RT_NULL, 1024, 25, 10);
    /* 创建成功则启动线程 */
    if (thread != RT_NULL)
    {
        rt_thread_startup(thread);
    }
    else
    {
        ret = RT_ERROR;
    }

return ret;
}

/* 导出到 msh 命令列表中 */
MSH_CMD_EXPORT(u, uart device sample);

```

![4fd122da71ebfa8b21fe990bf5ea6d84.png.webp](https://oss-club.rt-thread.org/uploads/20210609/4fd122da71ebfa8b21fe990bf5ea6d84.png.webp)