5 修改串口波特率的问题？

发布于 2023-08-15 16:48:29 浏览：1103 订阅该版

修改串口波特率，代码如下，去掉打印信息就是 close先关闭串口  control修改波特率 open打开串口
但是不成功，还是按照115200发送数据，BRR里也是0x16C

```c
rt_uint8_t change_baud(int baud)
{
    rt_uint8_t i = 0;
    rt_err_t flag = 100, flag_open = 100, flag_close = 100, flag_open2 = 100;//非法值，非RT_EOK
     struct serial_configure config = RT_SERIAL_CONFIG_DEFAULT;
      /* step1：查找串口设备 */
      serial = rt_device_find("uart4");
	
       rt_device_close( serial );
	
      config.baud_rate = baud;        //修改波特率为 9600
//      config.bufsz = 4096;

for(i = 0; i < 20; i++)//循环10次，成功的话跳出循环
      {
		  rt_kprintf("%d---------\n",i);
		  rt_kprintf(" before close ue = %0x\n", UART4->CR1);
		  flag_close = rt_device_close( serial );
		  rt_kprintf("flag_close = %d\n", flag_close);
		  USART_Cmd(UART4, DISABLE);
	rt_kprintf(" after close ue = %0x\n", UART4->CR1);
		  if (flag_close == RT_EOK)
		  {
			  rt_kprintf("serial close chenggong " );
		  }
		  rt_kprintf(" ue = %0x\n", UART4->CR1);
            flag = rt_device_control(serial, RT_DEVICE_CTRL_CONFIG, &config);
		  rt_kprintf("baud = %d brr = %0x\n", baud, UART4->BRR);
            if (flag == RT_EOK)
            {
				flag_open2 = rt_device_open(serial, RT_DEVICE_FLAG_DMA_RX);
				rt_kprintf("baud = %d brr = %0x\n", baud, UART4->BRR);
				rt_kprintf("flag_open2 = %d\n", flag_open2);
				rt_kprintf(" before open ue = %0x\n", UART4->CR1);
				USART_Cmd(UART4, ENABLE);
				rt_kprintf(" ofter open ue = %0x\n", UART4->CR1);
//				if (flag_open2 == RT_EOK)
			  {
				  rt_kprintf("serial open chenggong " );
			  }
                 rt_kprintf(" change baud %d success\n",baud);
                return 1;
            }
      }
   rt_kprintf(" change baud %d failed\n",baud); 
	  flag_open = rt_device_open(serial, RT_DEVICE_FLAG_DMA_RX);
	  rt_kprintf("flag_open = %d\n", flag_open);
		  if (flag_open == RT_EOK)
		  {
			  rt_kprintf("serial open chenggong " );
		  }
      return 0;
    //   rt_device_open(serial, RT_DEVICE_FLAG_DMA_RX);

}
```

自己写了一下，这样就可以了

```c
rt_uint8_t change_baud(int baud)
{

USART_Cmd(UART4, DISABLE);
	if (baud == 115200)
	{
		UART4->BRR = 0x16C;
	}
	else if (baud == 9600)
	{
		UART4->BRR = 0x1117;
	}
	USART_Cmd(UART4, ENABLE);
	
	
}
```

为什么我调用 close  control  open就不行呢？
如果不close  open，光control，也可以。但是切换波特率前后的数据有问题，怀疑的切换波特率导致的。

4 个回答

yangjie 认证专家 2023-08-16

hello

伊森亨特 2023-08-16

这家伙很懒，什么也没写！

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追加回复

a1012112796 2023-08-17

这家伙很懒，什么也没写！

出出啊 2023-08-17

恃人不如自恃，人之为己者不如己之自为也

伊森亨特 2023-08-17

这家伙很懒，什么也没写！

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凌晨 2023-08-17

这家伙很懒，什么也没写！

运行过程中动态修改串口配置参数
```c
void uart_config(rt_uint32_t baud)
{
    rt_device_t dev =RT_NULL;
    struct rt_serial_device *serial =RT_NULL;

struct serial_configure uart_config = \
            {                                          \
                BAUD_RATE_115200,  /* 115200 bits/s */  \
                DATA_BITS_8,      /* 8 databits */     \
                STOP_BITS_1,      /* 1 stopbit */      \
                PARITY_NONE,      /* none parity  */     \
                BIT_ORDER_LSB,    /* LSB first sent */ \
                NRZ_NORMAL,       /* Normal mode */    \
                RT_SERIAL_RB_BUFSZ, /* Buffer size */  \
                0                                      \
            };

dev = rt_device_find("uart4");
    if(dev !=RT_NULL)
    {
        serial = (struct rt_serial_device *)dev;
        //串口设备引用次数必须大于0，也就是说串口设备要处于open状态
		//并且串口buffer的大小不能改变，其大小为一开始初始化时的大小RT_SERIAL_RB_BUFSZ
        if((dev->ref_count >0) && (serial->config.bufsz == uart_config.bufsz))
        {
            uart_config.baud_rate =baud;
            rt_device_control(dev, RT_DEVICE_CTRL_CONFIG, &uart_config);
        }
    }
}
```