为什么我的串口读写不了数据，卡死在读数据那里了

发布于 2024-10-04 10:57:40 浏览：142 订阅该版

```c
#define SAMPLE_UART_NAME       "uart3"
static struct rt_semaphore rx_sem;
static rt_device_t serial;
rt_err_t ret = RT_EOK;
static rt_err_t uart_input(rt_device_t dev, rt_size_t size)
{
    rt_kprintf("Semaphore released.\n");
    rt_sem_release(&rx_sem);
    return RT_EOK;
}
```

![企业微信截图_17280105887618.png](https://oss-club.rt-thread.org/uploads/20241004/0f4d7c34a939fe68127a5ef9eee39438.png)

```c
static void serial_thread_entry(void *parameter)
{
    char ch;
    rt_kprintf("11111\n");
    while (1)
    {
        /* 从串口读取一个字节的数据，没有读取到则等待接收信号量 */
        while (rt_device_read(serial, 0, &ch, 1) != 1)
        {
            rt_kprintf("2222\n");
            /* 阻塞等待接收信号量，等到信号量后再次读取数据 */
            rt_sem_take(&rx_sem, RT_WAITING_FOREVER);
        }
        /* 读取到的数据通过串口错位输出 */
        rt_kprintf("33333\n");
        ch = ch + 1;
        rt_device_write(serial, 0, &ch, 1);
        rt_kprintf("Read: %c, Write: %c\n", ch - 1, ch);
    }

}

static int uart_sample()
{

char str[] = "sss!\n";

serial = rt_device_find(SAMPLE_UART_NAME);
   if (!serial)
   {
       rt_kprintf("find failed!\n");
       return RT_ERROR;
   }

/* 初始化信号量 */
   rt_sem_init(&rx_sem, "rx_sem", 1, RT_IPC_FLAG_PRIO);
   rt_device_open(serial, RT_DEVICE_FLAG_INT_RX);
   if (rt_device_open(serial, RT_DEVICE_FLAG_INT_RX)!=RT_EOK)
   {
       rt_kprintf("find failed!11111\n");
       return RT_ERROR;
   }
   rt_device_set_rx_indicate(serial, uart_input);
   rt_device_write(serial, 0, str, (sizeof(str) - 1));

rt_thread_t thread = rt_thread_create("serial", serial_thread_entry, RT_NULL, 1024, 25, 10);
   if (thread != RT_NULL)
   {
       rt_thread_startup(thread);
   }
   else
   {
       ret = RT_ERROR;
   }

}
int main()
{
    /* user app entry */

uart_sample();

//MSH_CMD_EXPORT(uart_sample, uart device sample);

while(1)
    {

rt_thread_mdelay(100);
    }

return 0;
}
```

1 个回答

YZRD 2024-10-06

这家伙很懒，什么也没写！

```
/*
 * 程序清单：这是一个 串口 设备使用例程
 * 例程导出了 uart_sample 命令到控制终端
 * 命令调用格式：uart_sample uart2
 * 命令解释：命令第二个参数是要使用的串口设备名称，为空则使用默认的串口设备
 * 程序功能：通过串口输出字符串"hello RT-Thread!"，然后错位输出输入的字符
*/

#include <rtthread.h>

#define SAMPLE_UART_NAME       "uart2"

/* 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_input(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 */
    rt_sem_release(&rx_sem);

return RT_EOK;
}

static void serial_thread_entry(void *parameter)
{
    char ch;

while (1)
    {
        /* 从串口读取一个字节的数据，没有读取到则等待接收信号量 */
        while (rt_device_read(serial, -1, &ch, 1) != 1)
        {
            /* 阻塞等待接收信号量，等到信号量后再次读取数据 */
            rt_sem_take(&rx_sem, RT_WAITING_FOREVER);
        }
        /* 读取到的数据通过串口错位输出 */
        ch = ch + 1;
        rt_device_write(serial, 0, &ch, 1);
    }
}

static int uart_sample(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_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
    {
        ret = RT_ERROR;
    }

return ret;
}
/* 导出到 msh 命令列表中 */
MSH_CMD_EXPORT(uart_sample, uart device sample);

```
官方例程：

![screenshot_image.png](https://oss-club.rt-thread.org/uploads/20241006/f3cc8077ddebc0a5da8f39bd358cbb43.png)