STM32F103 串口5 UART5 无法使用问题，不能接收和发送数据。

#define BSP_USING_UART1                       //DEBUG调试口
#define BSP_UART1_TX_PIN       "PA9"
#define BSP_UART1_RX_PIN       "PA10"
#define BSP_USING_UART2                       
#define BSP_UART2_TX_PIN       "PD5"
#define BSP_UART2_RX_PIN       "PD6"
#define BSP_UART2_RX_USING_DMA
#define BSP_UART2_TX_USING_DMA
#define BSP_USING_UART3                       
#define BSP_UART3_TX_PIN       "PB10"
#define BSP_UART3_RX_PIN       "PB11"
#define BSP_UART3_RX_USING_DMA
#define BSP_UART3_TX_USING_DMA
#define BSP_USING_UART4                       
#define BSP_UART4_TX_PIN       "PC10"
#define BSP_UART4_RX_PIN       "PC11"
#define BSP_UART4_RX_USING_DMA
#define BSP_UART4_TX_USING_DMA
#define BSP_USING_UART5        //串口5无DMA功能
#define BSP_UART5_TX_PIN       "PC12"
#define BSP_UART5_RX_PIN       "PD2"

uint8_t uart5_init(void)
{
    /* 查找串口设备 */
    uart5 = rt_device_find(UART_NAME);
    if (!uart5)
    {
        rt_kprintf("find %s failed!\n", UART_NAME);
        return RT_ERROR;
    }
    config.baud_rate = BAUD_RATE_115200;
    config.data_bits = DATA_BITS_8 ;
    config.stop_bits = STOP_BITS_1 ;
    config.parity    = PARITY_NONE ;
    config.bufsz     = 256 ;
    rt_device_control(uart5, RT_DEVICE_CTRL_CONFIG, &config);
    rt_device_open(display_uart, RT_DEVICE_OFLAG_RDWR|RT_DEVICE_FLAG_INT_RX);//去掉DMA的方式,以读写中断的方式打开。
    return 0;
}