1.结构体的声明需放在函数的最前面
源代码：
/*开启时钟*/RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1, ENABLE); //开启USART1的时钟RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE); //开启GPIOA的时钟/*GPIO初始化*/GPIO_InitTypeDef GPIO_InitStructure;GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9;GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;GPIO_Init(GPIOA, &GPIO_InitStructure); //将PA9引脚初始化为复用推挽输出GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IPU;GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;GPIO_Init(GPIOA, &GPIO_InitStructure); //将PA10引脚初始化为上拉输入/*USART初始化*/USART_InitTypeDef USART_InitStructure; //定义结构体变量USART_InitStructure.USART_BaudRate = 9600; //波特率USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None; //硬件流控制，不需要USART_InitStructure.USART_Mode = USART_Mode_Tx | USART_Mode_Rx; //模式，发送模式和接收模式均选择USART_InitStructure.USART_Parity = USART_Parity_No; //奇偶校验，不需要USART_InitStructure.USART_StopBits = USART_StopBits_1; //停止位，选择1位USART_InitStructure.USART_WordLength = USART_WordLength_8b; //字长，选择8位USART_Init(USART1, &USART_InitStructure); //将结构体变量交给USART_Init，配置USART1/*中断输出配置*/USART_ITConfig(USART1, USART_IT_RXNE, ENABLE); //开启串口接收数据的中断/*NVIC中断分组*/NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2); //配置NVIC为分组2/*NVIC配置*/NVIC_InitTypeDef NVIC_InitStructure; //定义结构体变量NVIC_InitStructure.NVIC_IRQChannel = USART1_IRQn; //选择配置NVIC的USART1线NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; //指定NVIC线路使能NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1; //指定NVIC线路的抢占优先级为1NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1; //指定NVIC线路的响应优先级为1NVIC_Init(&NVIC_InitStructure); //将结构体变量交给NVIC_Init，配置NVIC外设/*USART使能*/USART_Cmd(USART1, ENABLE); //使能USART1，串口开始运行
会报错
这里错误信息提示我们，“声明不能出现在可执行语句之后”
那么修改为
GPIO_InitTypeDef GPIO_InitStructure;USART_InitTypeDef USART_InitStructure; //定义结构体变量 NVIC_InitTypeDef NVIC_InitStructure; //定义结构体变量/*开启时钟*/RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1, ENABLE); //开启USART1的时钟RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE); //开启GPIOA的时钟/*GPIO初始化*/GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9;GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;GPIO_Init(GPIOA, &GPIO_InitStructure); //将PA9引脚初始化为复用推挽输出GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IPU;GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;GPIO_Init(GPIOA, &GPIO_InitStructure); //将PA10引脚初始化为上拉输入/*USART初始化*/USART_InitStructure.USART_BaudRate = 9600; //波特率USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None; //硬件流控制，不需要USART_InitStructure.USART_Mode = USART_Mode_Tx | USART_Mode_Rx; //模式，发送模式和接收模式均选择USART_InitStructure.USART_Parity = USART_Parity_No; //奇偶校验，不需要USART_InitStructure.USART_StopBits = USART_StopBits_1; //停止位，选择1位USART_InitStructure.USART_WordLength = USART_WordLength_8b; //字长，选择8位USART_Init(USART1, &USART_InitStructure); //将结构体变量交给USART_Init，配置USART1/*中断输出配置*/USART_ITConfig(USART1, USART_IT_RXNE, ENABLE); //开启串口接收数据的中断/*NVIC中断分组*/NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2); //配置NVIC为分组2/*NVIC配置*/NVIC_InitStructure.NVIC_IRQChannel = USART1_IRQn; //选择配置NVIC的USART1线NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; //指定NVIC线路使能NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1; //指定NVIC线路的抢占优先级为1NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1; //指定NVIC线路的响应优先级为1NVIC_Init(&NVIC_InitStructure); //将结构体变量交给NVIC_Init，配置NVIC外设/*USART使能*/USART_Cmd(USART1, ENABLE);
将结构体声明放在最前面，程序就不报错了。
