【前提】
实际应用中，芯片型号为STM32F030CCT6,串口1用于模组通讯，串口2用于仪表通讯，串口3用于调试，log输出

串口1配置

void USART1_Config(u32 baud)
{
	GPIO_InitTypeDef GPIO_InitStructure;
	USART_InitTypeDef USART_InitStructure;
	NVIC_InitTypeDef	NVIC_InitStructure;

	RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1, ENABLE);//开启时钟
	RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOA, ENABLE);
	GPIO_PinAFConfig(GPIOA, GPIO_PinSource9, GPIO_AF_1);  //引脚复用配置
	GPIO_PinAFConfig(GPIOA, GPIO_PinSource10, GPIO_AF_1); 

	USART_InitStructure.USART_BaudRate = baud;   
	USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;    
	USART_InitStructure.USART_Mode = USART_Mode_Tx|USART_Mode_Rx;   
	USART_InitStructure.USART_StopBits = USART_StopBits_1;    
	USART_InitStructure.USART_WordLength = USART_WordLength_8b;
	USART_InitStructure.USART_Parity = USART_Parity_No;

	USART_Init(USART1,&USART_InitStructure);
	USART_ITConfig(USART1, USART_IT_RXNE, ENABLE);
	USART_Cmd(USART1, ENABLE);

	GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9| 	GPIO_Pin_10;   	
	GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;  		//复用模式  
	GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;   		//推挽输出
	GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;			
	GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;  	//串口的应用波特率最大115200.2M足够，既省电噪声也小 
	GPIO_Init(GPIOA, &GPIO_InitStructure); 
	
	NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
	NVIC_InitStructure.NVIC_IRQChannel = USART1_IRQn;
	NVIC_InitStructure.NVIC_IRQChannelPriority = 0;
	NVIC_Init(&NVIC_InitStructure);
}

串口2配置

方式类似，此处省略…

串口3配置

void USART3_Config(u32 baud)
{
	GPIO_InitTypeDef GPIO_InitStructure;
	USART_InitTypeDef USART_InitStructure;
	NVIC_InitTypeDef	NVIC_InitStructure;

	RCC_APB1PeriphClockCmd( RCC_APB1Periph_USART3, ENABLE);
	RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOB, ENABLE);
	GPIO_PinAFConfig(GPIOB, GPIO_PinSource10, GPIO_AF_4);  //引脚复用配置
	GPIO_PinAFConfig(GPIOB, GPIO_PinSource11, GPIO_AF_4); 

	USART_InitStructure.USART_BaudRate = baud;   
	USART_InitStructure.USART_HardwareFlowControl = 							USART_HardwareFlowControl_None;    
	USART_InitStructure.USART_Mode = USART_Mode_Tx|USART_Mode_Rx;   
	USART_InitStructure.USART_StopBits = USART_StopBits_1;    
	USART_InitStructure.USART_WordLength = USART_WordLength_8b;
	USART_InitStructure.USART_Parity = USART_Parity_No;

	USART_Init(USART3,&USART_InitStructure);
	USART_ITConfig(USART3, USART_IT_RXNE, ENABLE);
	USART_Cmd(USART3, ENABLE);

	GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10| 	GPIO_Pin_11;   	
	GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;  		//复用模式  
	GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;   		//推挽输出
	GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;			
	GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;  	
	GPIO_Init(GPIOB, &GPIO_InitStructure); 
	
	NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
	NVIC_InitStructure.NVIC_IRQChannel = USART3_6_IRQn;
	NVIC_InitStructure.NVIC_IRQChannelPriority = 2;
	NVIC_Init(&NVIC_InitStructure);
}

注意事项

1. 开启引脚复用功能时，引脚为 GPIO_PinSourcex，不是 GPIO_pins_define，否则串口会配置失败，进入硬件中断，习惯使用STM32F103系列的，这里很容易出错
   GPIO_PinAFConfig(GPIOB, GPIO_PinSource10, GPIO_AF_4);
   
2. 启动文件要选择startup_stmf030xc.s
   中断向量表中有USART3_6_IRQHandler，否则产生中断时找不到中断入口地址
   注：startup_stmf030.s中没有USART3_6_IRQHandler
   
3. 需要打开STM32F030xC宏定义，才会有中断向量USART3_6_IRQn的定义
   

方式1：在stm32f0xx.h中打开注释 #define STM32F030xC

方式2：在工程魔法棒中添加

5. 因为串口3-6共用一个中断函数，当进入中断时，需要判断具体哪个串口

void USART3_6_IRQHandler(void)
{
	if(USART_GetITStatus(USART3, USART_IT_RXNE) == SET)
	{
		USART3_ReceiveLongData();
		USART_ClearFlag(USART3,USART_FLAG_RXNE);
	}
}

6.在进行串口配置时，最好先初始化串口再进行IO口配置，串口没初始化前可能有浮空电平，导致设备刚上电时串口乱发数据的问题