STM32 的 USART 使能USART_IT_RXNE进不了中断，USART_IT_TXE就能进

void USART_Configure()

{

    GPIO_InitTypeDef GPIO_InitStructure;
    USART_InitTypeDef USART_InitStructure;
    NVIC_InitTypeDef NVIC_InitStructure;

    RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1,ENABLE );
    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);

    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9 |GPIO_Pin_10;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
    GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
    GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
    GPIO_Init(GPIOA, &GPIO_InitStructure);

    GPIO_PinAFConfig(GPIOA,GPIO_PinSource9,GPIO_AF_USART1);
    GPIO_PinAFConfig(GPIOA,GPIO_PinSource10,GPIO_AF_USART1);

    USART_InitStructure.USART_BaudRate = 115200;
    USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
    USART_InitStructure.USART_Mode = USART_Mode_Rx |USART_Mode_Tx;
    USART_InitStructure.USART_Parity = USART_Parity_No;
    USART_InitStructure.USART_StopBits = USART_StopBits_1;
    USART_InitStructure.USART_WordLength = USART_WordLength_8b;
    USART_Init(USART1,&USART_InitStructure);

    USART_Cmd(USART1,ENABLE);
    USART_ClearFlag(USART1,USART_FLAG_RXNE); 
    USART_ITConfig(USART1,USART_IT_RXNE,ENABLE);//USART_IT_TXE

    /*  中断*/
    NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2);//优先级分布
    NVIC_InitStructure.NVIC_IRQChannel = USART1_IRQn;
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 3;
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 3;
    NVIC_Init(&NVIC_InitStructure);

}

void USART1_IRQHandler(void)

{

    u8 res;

    if(USART_GetITStatus(USART1,USART_IT_RXNE)==SET)
    {
        USART_ClearFlag(USART1,USART_FLAG_RXNE);  
        USART_ClearITPendingBit(USART1,USART_IT_RXNE);

        res = USART_ReceiveData(USART1);
        USART_SendData(USART1,res);
    } 

    while (1)
    {
        USART_SendData(USART1,'C');
        while(RESET == USART_GetFlagStatus(USART1,USART_FLAG_TXE));
    }

}

//

int main(void)

{

    SystemInit();

    USART_Configure();

    delay(1000);


    while (1)
    {
        USART_SendData(USART1,'a');
        while(RESET == USART_GetFlagStatus(USART1,USART_FLAG_TXE));
        delay(1000);
    }

}

http://www.openedv.com/posts/list/22101.htm

可能是固件库版本太低了，你下一个最新的