RTT串口初始化，只能发送，不能接收数据

#define RT_USING_UART3 
#ifdef RT_USING_UART3
    /* Enable UART GPIO clocks */
    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOB, ENABLE);
    /* Enable UART clock */
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART3, ENABLE);
#endif /* RT_USING_UART3 */
#if defined(RT_USING_UART3)
/* UART3 device driver structure */
struct stm32_uart uart3 =
{
    USART3,
    USART3_IRQn,
};
struct rt_serial_device serial3;
void USART3_IRQHandler(void)
{
    struct stm32_uart* uart;
    uart = &uart3;
    /* enter interrupt */
    rt_interrupt_enter();
    if(USART_GetITStatus(uart->uart_device, USART_IT_RXNE) != RESET)
    {
        rt_hw_serial_isr(&serial3, RT_SERIAL_EVENT_RX_IND);
        /* clear interrupt */
        USART_ClearITPendingBit(uart->uart_device, USART_IT_RXNE);
    }
    if (USART_GetITStatus(uart->uart_device, USART_IT_TC) != RESET)
    {
        /* clear interrupt */
        USART_ClearITPendingBit(uart->uart_device, USART_IT_TC);
    }
    if (USART_GetFlagStatus(uart->uart_device, USART_FLAG_ORE) == SET)
    {
        stm32_getc(&serial3);
    }
    /* leave interrupt */
    rt_interrupt_leave();
}
#endif /* RT_USING_UART3 */
#if defined(RT_USING_UART3)
    GPIO_PinAFConfig(UART3_GPIO, GPIO_PinSource10, GPIO_AF_USART3);//备用屏幕口
        GPIO_PinAFConfig(UART3_GPIO, GPIO_PinSource11, GPIO_AF_USART3);
    /* Configure USART Rx/tx PIN */
      GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;        
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
    GPIO_InitStructure.GPIO_Pin = UART3_GPIO_RX;
    GPIO_Init(UART3_GPIO, &GPIO_InitStructure);
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
    GPIO_InitStructure.GPIO_Pin = UART3_GPIO_TX;
    GPIO_Init(UART3_GPIO, &GPIO_InitStructure);
#endif /* RT_USING_UART3 */
#if defined(RT_USING_UART3)
    uart = &uart3;
    config.baud_rate = BAUD_RATE_115200;
    serial3.ops    = &stm32_uart_ops;
    serial3.config = config;
    NVIC_Configuration(&uart3);
    /* register UART1 device */
    rt_hw_serial_register(&serial3, "uart3",
                          RT_DEVICE_FLAG_RDWR | RT_DEVICE_FLAG_INT_RX,
                          uart);
#endif /* RT_USING_UART3 */
#define SAMPLE_UART_NAME       "uart3"       /* 需要操作的设备 */
static rt_device_t serial;                   /* 设备句柄 */
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 int uart_sample(void)
{
    rt_err_t ret = RT_EOK;char ch;
    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(SAMPLE_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));
     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) == 0)
        {
            /* 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);
    }
    return ret;
}