串口发送

5 为什么用串口发送一帧数据，会断开？

发布于 2022-08-05 19:50:18 浏览：244 订阅该版

代码如下：发送400左右个字节
```c
rt_device_write(dev, 0, USART3_TX_BUF, n);
```
然后串口调试助手显示如下：

![screenshot_图片.png](https://oss-club.rt-thread.org/uploads/20220805/b9f5ca4ed639f14a85ecdb70bc3503be.png.webp)

问题1：为什么一帧数据之间有几十ms的间隔呢？这样导致我的从机不会认为它是一帧了。我需要在发送的时候关闭调度器吗？
问题2：我在接收的时候也是这样，把一帧数据打断。同事用的3.1.2版本，他的device_read可以一次读一帧数据，几百个字节，我读到的都是断开的。

补充信息**补充信息 8.7.9：43**
04 10 01 00 00 C9 01 92 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
32个字节
时间是40.612——40.657，一个字节1.40625ms，1位是0.17578125，1s发5688.88，相当于波特率是这个
9600波特率，一个字节，起始，8位字长，1停止，10个bit位，1s中9600个比特位，960个字节，一个字节1.0416666ms

百度了一下，超过2个字节的时间，就认为产生空闲中断了。9600是2ms左右，我这也没超过啊，偶尔也有这种情况，这种应该超过了42ms 6个字节

![screenshot_图片.png](https://oss-club.rt-thread.org/uploads/20220807/21b2bfaea7787603cfc8e92b77227ff4.png)

怎么在线程切换的时候打印一个信息呢？比如进入这个线程，或者离开这个线程的时候，我看看是因为线程切换，还是因为啥。

线程时间片拉长到150ms了，不好使啊。添加了dma发送模式 试试，
**8.8 9：26添加**
可以看到，接收的时候，第一帧是串口助手发的，第二帧是从机响应的。主机接收的时候，把他俩当成一帧了，下面open time tick是主机每次调用device read成功时开启定时器的时间，他把这些分成了3份  共388个字节，时间是394-155 = 249ms，一个字节	0.6417,为什么这么快呢

![screenshot_图片.png](https://oss-club.rt-thread.org/uploads/20220808/9176ae47b99148ae81528e4470c191d2.png.webp)

![screenshot_图片.png](https://oss-club.rt-thread.org/uploads/20220808/540bf94e04a139cdebe1e503a7626c05.png.webp)

现在用超时判断一帧的时候，200ms才能保证接收不出错，150ms偶尔接收会失败。这太变态了，哪个串口同一帧数据，间隔了150ms

8 个回答

aozima 2022-08-05

调网络不抓包，调I2C等时序不上逻辑分析仪，就像电工不用万用表！

伊森亨特 2022-08-05

This guy hasn't written anything yet

aozima 2022-08-05

调网络不抓包，调I2C等时序不上逻辑分析仪，就像电工不用万用表！

伊森亨特 2022-08-05

This guy hasn't written anything yet

aozima 6 days ago

调网络不抓包，调I2C等时序不上逻辑分析仪，就像电工不用万用表！

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JonasWen 2022-08-05

这家伙不懒，但是什么也不想写！

伊森亨特 2022-08-05

This guy hasn't written anything yet

伊森亨特 2022-08-05

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JonasWen 6 days ago

这家伙不懒，但是什么也不想写！

伊森亨特 4 days ago

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lchnu 2022-08-05

Witness, Understand, Skill

伊森亨特 2022-08-05

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lchnu 2022-08-05

Witness, Understand, Skill

伊森亨特 6 days ago

This guy hasn't written anything yet

lchnu 6 days ago

Witness, Understand, Skill

伊森亨特 6 days ago

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出出啊 6 days ago

It is Not the Mountain We Conquer, but Ourselves

伊森亨特 6 days ago

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出出啊 5 days ago

It is Not the Mountain We Conquer, but Ourselves

伊森亨特 5 days ago

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aprilhome 5 days ago

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伊森亨特 4 days ago

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胡图图 4 days ago

This guy hasn't written anything yet

伊森亨特 4 days ago

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胡图图 4 days ago

This guy hasn't written anything yet

胡图图 4 days ago

This guy hasn't written anything yet

伊森亨特 4 days ago

This guy hasn't written anything yet

伊森亨特 4 days ago

This guy hasn't written anything yet

```c
while(1)
	{
//		rt_kprintf("read_uart thread\n");
		rt_thread_delay(50);
		 if (timeout == 1 && old_recv_cnt != 0 && recv_cnt == 0)
		//if (rt_sem_take(&recv_comp,0) == RT_EOK)
		{
			
			timeout = 0;
			old_recv_cnt = 0;
			
			tmp_ptr = recv_buff;
			rt_device_control(hw_dev, HWTIMER_CTRL_STOP, RT_NULL);
			dump_hex(recv_buff, cnt);//调试用
			rt_memcpy(USART3_RX_BUF,recv_buff,sizeof(USART3_RX_BUF));//数据给USART3_RX_BUF
			USART3_RX_LEN = cnt;//得到有效数据长度
			
			
			
			rt_sem_release(&recv_comp);
			rt_kprintf("receive one frame done! ：%d\n", rt_tick_get());
			recv_ok = 1;
			cnt = 0;
			cnt_test = 0;
		}
		
		if (rt_sem_take(&env_rx,500) != RT_EOK)
		{
			
			continue;
		}
		else
		{
			cnt_test++;
			//rt_kprintf("di %d ci release semaphore\n",cnt_test);
		}
		while (recv_cnt = rt_device_read(dev, -1, tmp_ptr, 4096)  )
        {
			if (DTU_flag == 1)
			{
				rt_device_control(hw_dev, HWTIMER_CTRL_STOP, RT_NULL);
				rt_uint32_t i = 0;
				for (rt_uint32_t i = 0;i<recv_cnt;i++)
				{
						rt_kprintf("%c", *(tmp_ptr+i));
				}
				
//				rt_sem_release(&recv_comp);
			}
			else
			{//从串口读到数据后，开启一个230ms的定时器，把收到的数据放到大的缓冲区里
				rt_device_write(hw_dev, 0, &timeout_s, sizeof(timeout_s)) ;
				rt_kprintf("open time tick = %d\n",rt_tick_get());
				cnt += recv_cnt;
				tmp_ptr += recv_cnt;
				old_recv_cnt = recv_cnt;
				rt_kprintf("recv_cnt = %d    cnt=%d \n",recv_cnt,cnt);
			}

}

}
我思路是这样的
从串口读到数据后，开启一个230ms的定时器，把收到的数据放到大的缓冲区里，每次收到一帧当中的一段，都开启定时器，把数据放到大的缓冲区里。当过了230ms，定时器溢出，全局变量timeout为0，说明没有从device read里得到数据，认为一帧数据接收完成。
这个230ms是实验测的，比这个小的话，会接受不完一帧，中间并没有进行其他处理。

伊森亨特 4 days ago

This guy hasn't written anything yet

[@胡图图](https://club.rt-thread.org/u/f540cea0473e3f80 '胡图图')

```c
while(1)
	{
//		rt_kprintf("read_uart thread\n");
		rt_thread_delay(50);
		 if (timeout == 1 && old_recv_cnt != 0 && recv_cnt == 0)
		//if (rt_sem_take(&recv_comp,0) == RT_EOK)
		{
			
			timeout = 0;
			old_recv_cnt = 0;
			
			tmp_ptr = recv_buff;
			rt_device_control(hw_dev, HWTIMER_CTRL_STOP, RT_NULL);
			dump_hex(recv_buff, cnt);//调试用
			rt_memcpy(USART3_RX_BUF,recv_buff,sizeof(USART3_RX_BUF));//数据给USART3_RX_BUF
			USART3_RX_LEN = cnt;//得到有效数据长度
			
			
			
			rt_sem_release(&recv_comp);
			rt_kprintf("receive one frame done! ：%d\n", rt_tick_get());
			recv_ok = 1;
			cnt = 0;
			cnt_test = 0;
		}
		
		if (rt_sem_take(&env_rx,500) != RT_EOK)
		{
			
			continue;
		}
		else
		{
			cnt_test++;
			//rt_kprintf("di %d ci release semaphore\n",cnt_test);
		}
		
		while (recv_cnt = rt_device_read(dev, -1, tmp_ptr, 4096)  )
        {
			if (DTU_flag == 1)
			{
				rt_device_control(hw_dev, HWTIMER_CTRL_STOP, RT_NULL);
				rt_uint32_t i = 0;
				for (rt_uint32_t i = 0;i<recv_cnt;i++)
				{
						rt_kprintf("%c", *(tmp_ptr+i));
				}
				
//				rt_sem_release(&recv_comp);
			}
			else
			{
				rt_device_write(hw_dev, 0, &timeout_s, sizeof(timeout_s)) ;
			
				rt_kprintf("open time tick = %d\n",rt_tick_get());
				cnt += recv_cnt;
				tmp_ptr += recv_cnt;
				old_recv_cnt = recv_cnt;
				rt_kprintf("recv_cnt = %d    cnt=%d \n",recv_cnt,cnt);
			}
			
			
            
        }

}
```

伊森亨特 4 days ago

This guy hasn't written anything yet

[@胡图图](https://club.rt-thread.org/u/f540cea0473e3f80 '胡图图')
我看你的代码，是定时器超时后，直接就把数据发到消息队列里了，没有进行判断是否在接收啊。你是在判断字节和字节之间的时间是否超过10ms，对吗？
```c
static rt_err_t uart9_input(rt_device_t dev, rt_size_t size)
{
    rt_err_t result;

Uart9_RxLine += size;
    
    if (Rx9_flag_begin == RT_FALSE)
    {
        /* 首次触发开启软件定时器 */
        rt_timer_start(uart9_timer_rxdone);
    }
    else
    {
        rt_timer_stop(uart9_timer_rxdone);
        rt_timer_control(uart9_timer_rxdone, RT_TIMER_CTRL_SET_TIME, RT_TICK_PER_SECOND/10);
        rt_timer_start(uart9_timer_rxdone);
    }

return result;
}

/* 串口接收超时 Callback */
void uart9_timeout_process(void)
{
    /* code */
    rt_err_t result;
    int rx9_length = 0;
    struct rx_msg msg_rx;
    memset(&msg_rx, 0, sizeof(struct rx_msg));

rx9_length = rt_device_read(serial9, 0, msg_rx.data, Uart9_RxLine);
    if (rx9_length > 0)
    {
        rt_kprintf("rx9_length = %d \n", rx9_length);
    }
    msg_rx.size = Uart9_RxLine;

result = rt_mq_send(uart9_rx_mq, &msg_rx, sizeof(struct rx_msg));
    if (result == -RT_EFULL)
    {
        /* 消息队列满 */
        rt_kprintf("uart9 message queue full！\n");
    }
}

```
你是在接收线程里读取消息队列，然后进行超时判断，从消息队列里接收数据