10 串口定时器超时接收，时间间隔过大？

发布于 2022-08-15 10:20:21 浏览：757 订阅该版

我现在采用串口接收，device从串口读出数据，根据超时时间判断一帧数据是否完成。现在的问题是超时时间要设置成230ms，才可以不出错的接收数据。如果时间短了，会把一帧数据分成两部分

如图所示，一帧数据424字节，每次接收数据是150多，或者18个。
主要代码在下面，请问424个字节，这么多时间间隔是什么原因造成的，怎么分析呢？谢谢

![screenshot_图片.png](https://oss-club.rt-thread.org/uploads/20220815/4d1b01a2c94d16dff8330040e674b871.png.webp)

接收函数
```c
void read_uart(void *parameter)
{
	rt_uint32_t recv_cnt = 0, old_recv_cnt = 0;
	rt_uint8_t 	recv_buff[4096] = {0};
	rt_uint8_t	*tmp_ptr= recv_buff;
	rt_uint16_t cnt = 0;//统计一次接收读取几次，可以知道一帧数据被dma分成几次
	rt_uint16_t cnt_test = 0;
	rt_tick_t open_tick = 0;
	rt_hwtimerval_t timeout_s;      /* 定时器超时值 */
	timeout_s.sec = 0;      /* 秒 */
    timeout_s.usec = 230000;     /* 微秒  100ms的时候是正常的，但是DTU数据间隔大，改成这个试试 DTU用延时做了  230ms正常，时间有点长*/
   	
	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,1000) != 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;
//				//用串口6通过DTU发送给云端
//				rt_device_write(dtu_dev, 0, tmp_ptr, recv_cnt);
				// 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);
			}
			
			
            
        }

}
	
}
```

串口回调函数
```c
rt_err_t env_recv_ind(rt_device_t dev, rt_size_t size)
{
    /* release semaphore to let finsh thread rx data */
	if (size > 0)
		rt_sem_release(&env_rx);
    return RT_EOK;
}
```
定时器超时函数
```c
void dtu_recv_timer_timeout(void *para)
{
	USART6_RX_LEN = rt_device_read(dtu_dev, 0, USART6_RX_BUF, 1024);
	dtu_flag = 1;
	dtu_recv_cnt = 0;
}	
```