今天在使用STM32F1芯片的USART3接口调试创乐博WIFI模块时发下接收的数据全是0，检查接线没有问题，USART3管角配置没错（复用推挽输出和浮空输入）、WIfi波特率等参数没错配置时没有发现什么问题。在网上找了同类问题的答案，都没能解决问题，于是怀疑是USART RX端口配置问题，于是将其设置为GPIO_Mode_IPU后接收正确。

下面是USART正确配置后的代码：

void usart3_init(u32 bound)
{  
    NVIC_InitTypeDef NVIC_InitStructure;
    GPIO_InitTypeDef GPIO_InitStructure;
    USART_InitTypeDef USART_InitStructure;
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB, ENABLE);
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART3, ENABLE);

    USART_DeInit(USART3);  //复位串口3
    //USART3_TX   PB10
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10; //PB10
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP; //复用推挽输出
    GPIO_Init(GPIOB, &GPIO_InitStructure); //初始化PB10
    //USART3_RX   PB11
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_11;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IPU ;//上拉输入(创乐博WIFI模块需要设置为上拉输入，其它的可能是下拉或浮空输入)
    GPIO_Init(GPIOB, &GPIO_InitStructure);  //初始化PB11
            
    //设置中断优先级
    NVIC_InitStructure.NVIC_IRQChannel = USART3_IRQn;
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority=3 ;//抢占优先级3
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 3;      //子优先级3
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;         //IRQ通道使能
    NVIC_Init(&NVIC_InitStructure); //根据指定的参数初始化VIC寄存器
    
    USART_InitStructure.USART_BaudRate = bound;//波特率一般设置为9600;
    USART_InitStructure.USART_WordLength = USART_WordLength_8b;//字长为8位数据格式
    USART_InitStructure.USART_StopBits = USART_StopBits_1;//一个停止位
    USART_InitStructure.USART_Parity = USART_Parity_No;//无奇偶校验位
    USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;//无硬件数据流控制
    USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx; //收发模式
    USART_Init(USART3, &USART_InitStructure); //初始化串口3
    
       USART_ITConfig(USART3, USART_IT_RXNE, ENABLE);//开启中断   

    USART_Cmd(USART3, ENABLE);                    //使能串口 

    USART3_RX_STA = 0;
}

void USART3_IRQHandler(void)  {
    u8 Res;
    char i = 0;
    if(USART_GetITStatus(USART3, USART_IT_RXNE) != RESET) 
    {
        Res = USART_ReceiveData(USART3);    //读取接收到的数据
        
        USART3_RX_BUF[USART3_RX_STA++]=Res ;

                // 串口1输出收到的内容
        printf("USERT3 Recv: ");
        for (i = 0; i < USART3_RX_STA; i++){
            printf(" %x[%c]", USART3_RX_BUF[i], USART3_RX_BUF[i]);
        }   
        printf("\r\n");     
     } 
}