10 串口设备发送的dev->ref_count为0

发布于 2022-07-22 16:23:28 浏览：791 订阅该版

```c
rt_size_t rt_device_write(rt_device_t dev,
                          rt_off_t    pos,
                          const void *buffer,
                          rt_size_t   size)
{
    /* parameter check */
    RT_ASSERT(dev != RT_NULL);
    RT_ASSERT(rt_object_get_type(&dev->parent) == RT_Object_Class_Device);

if (dev->ref_count == 0)
    {
        rt_set_errno(-RT_ERROR);
        return 0;
    }

/* call device_write interface */
    if (device_write != RT_NULL)
    {
        return device_write(dev, pos, buffer, size);
    }

/* set error code */
    rt_set_errno(-RT_ENOSYS);

return 0;
}
```
初始化串口的代码如下，就是find，open
```c
rt_err_t env_ctrl_xfer_init(void)
{
	rt_err_t	result1,result2;
	
    struct serial_configure pconfig;
	/* 初始化串口 */
    if (dev == RT_NULL)
    {
        dev = rt_device_find(ENV_NAME);
        RT_ASSERT(dev);

pconfig.baud_rate = BAUD_RATE_9600;
        pconfig.data_bits = DATA_BITS_8;
        pconfig.stop_bits = STOP_BITS_1;
        pconfig.parity    = PARITY_NONE;
        pconfig.bit_order = BIT_ORDER_LSB;
        pconfig.invert    = NRZ_NORMAL;
        pconfig.bufsz     = 6144;
        pconfig.reserved  = 0;
        /* 设置串口参数 */
        rt_device_control(dev, RT_DEVICE_CTRL_CONFIG, &pconfig);
        /*设置串口的回调函数 */
        rt_device_set_rx_indicate(dev, env_recv_ind);
    }
	if(RT_EOK ==rt_device_open(dev, RT_DEVICE_FLAG_DMA_RX))
```
对了，这里使用DMA的话，需要在env里打开BSP_UART3_RX_USING_DMA吗？需要在cubemx打开dma配置吗？谢谢