MM32F103_n版单片机UART不能使用问题

UART1默认RX/TX引脚为PA9和PA10，

现重定义到PB6和PB7，

修改后程序如下，使能UART1和GPIOB时钟，初始化IO、中断、UART相关配置，使能串口中断。
void TEST_Uart_Configuration(void)
{
    GPIO_InitTypeDef GPIO_InitStructure;
    UART_InitTypeDef USART_InitStructure;
    NVIC_InitTypeDef NVIC_InitStructure;
                           
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_UART1, ENABLE);
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB, ENABLE);

      
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6;
    GPIO_Init(GPIOB, &GPIO_InitStructure);

    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_7;
    GPIO_Init(GPIOB, &GPIO_InitStructure);    

    NVIC_InitStructure.NVIC_IRQChannel = UART1_IRQn;
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStructure);
    USART_InitStructure.UART_BaudRate = 115200;
    USART_InitStructure.UART_WordLength = UART_WordLength_8b;
    USART_InitStructure.UART_StopBits = UART_StopBits_1;
    USART_InitStructure.UART_Parity = UART_Parity_No;
    USART_InitStructure.UART_HardwareFlowControl = UART_HardwareFlowControl_None;
    USART_InitStructure.UART_Mode = UART_Mode_Rx | UART_Mode_Tx;
    UART_Init(UART1, &USART_InitStructure);
    UART_ITConfig(UART1, UART_IT_RXIEN, ENABLE); 
    UART_Cmd(UART1, ENABLE); 
}
编译下载后串口无法使用，检查后发现，修改引脚使用重定义需要使用remap寄存器，需要使能GPIO_Remap_UART1，
因此要调用
 GPIO_PinRemapConfig(GPIO_Remap_UART1,ENABLE);
将UART1管脚重映射。
而使用重映射功能需要使能AFIO时钟，可调用RCC_APB2PeriphClockCmd函数使能RCC_APB2Periph_AFIO，

    RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO, ENABLE);
修改后程序如下：

void TEST_Uart_Configuration(void)
{
    GPIO_InitTypeDef GPIO_InitStructure;
    UART_InitTypeDef USART_InitStructure;
    NVIC_InitTypeDef NVIC_InitStructure;
                           
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_UART1, ENABLE);
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB, ENABLE);

    RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO, ENABLE);

      
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6;
    GPIO_Init(GPIOB, &GPIO_InitStructure);

    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_7;
    GPIO_Init(GPIOB, &GPIO_InitStructure);
    
    GPIO_PinRemapConfig(GPIO_Remap_UART1,ENABLE);
    
    NVIC_InitStructure.NVIC_IRQChannel = UART1_IRQn;
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStructure);
    
    
    USART_InitStructure.UART_BaudRate = 115200;  //2¨ì??ê
    USART_InitStructure.UART_WordLength = UART_WordLength_8b;  //8??êy?Y?￡ê?
    USART_InitStructure.UART_StopBits = UART_StopBits_1;  //í￡?1?? 1??
    USART_InitStructure.UART_Parity = UART_Parity_No;
    USART_InitStructure.UART_HardwareFlowControl = UART_HardwareFlowControl_None;
    USART_InitStructure.UART_Mode = UART_Mode_Rx | UART_Mode_Tx;
    UART_Init(UART1, &USART_InitStructure);
    UART_ITConfig(UART1, UART_IT_RXIEN, ENABLE); 
    UART_Cmd(UART1, ENABLE); 
}