在配置USART和UART之前，得先明白什么是USART和UART以及它们之间有什么区别，其实两者是同步和异步的区别。
UART：universal asynchronous receiver and transmitter通用异步收发器；
USART：universal synchronous asynchronous receiver and transmitter通用同步异步收发器。
一般而言，单片机中，名称为UART的接口一般只能用于异步串行通讯，而名称为USART的接口既可以用于同步串行通讯，也能用于异步串行通讯。
串口接受和发送数据的程序（USART/UART）
STM32串口引脚如下图所示
一、配置USART1
static unsigned char TxBuffer[256];
static unsigned char TxCounter=0;
static unsigned char count=0;
extern void CopeSerial1Data(unsigned char ucData);
void Initial_UART1(unsigned long baudrate)
{//GPIO端口设置GPIO_InitTypeDef GPIO_InitStructure;USART_InitTypeDef USART_InitStructure;NVIC_InitTypeDef NVIC_InitStructure; RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1 | RCC_APB2Periph_GPIOA, ENABLE);//USART1_TX GPIOA.9GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9;GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;//复用推挽输出GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;GPIO_Init(GPIOA, &GPIO_InitStructure); //初始化 //USART1_RX GPIOA.10GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;//浮空输入GPIO_Init(GPIOA, &GPIO_InitStructure);//初始化USART_InitStructure.USART_BaudRate = baudrate;//设置波特率USART_InitStructure.USART_WordLength = USART_WordLength_8b;//字长为8位数据格式USART_InitStructure.USART_StopBits = USART_StopBits_1;//1个停止位USART_InitStructure.USART_Parity = USART_Parity_No ;//无奇偶校验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(USART1, &USART_InitStructure); //初始化USART_ITConfig(USART1, USART_IT_TXE, DISABLE); USART_ITConfig(USART1, USART_IT_RXNE, ENABLE); //开启串口接受中断 USART_ClearFlag(USART1,USART_FLAG_TC);USART_Cmd(USART1, ENABLE);//使能NVIC_InitStructure.NVIC_IRQChannel = USART1_IRQn;NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1;NVIC_InitStructure.NVIC_IRQChannelSubPriority = 7;NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;NVIC_Init(&NVIC_InitStructure);
}
二、配置USART2
由于和前一个配置大同小异，所以只在和前一个不同的地方加入注释
static unsigned char TxBuffer[256];
static unsigned char TxCounter=0;
static unsigned char count=0;
extern void CopeSerial2Data(unsigned char ucData);
void Initial_UART2(unsigned long baudrate)
{GPIO_InitTypeDef GPIO_InitStructure;USART_InitTypeDef USART_InitStructure;NVIC_InitTypeDef NVIC_InitStructure; RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART2 | RCC_APB2Periph_GPIOA, ENABLE);//PA2为TXGPIO_InitStructure.GPIO_Pin = GPIO_Pin_2;GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;GPIO_Init(GPIOA, &GPIO_InitStructure); //PA3为RX GPIO_InitStructure.GPIO_Pin = GPIO_Pin_3;GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;GPIO_Init(GPIOA, &GPIO_InitStructure);USART_InitStructure.USART_BaudRate = baudrate;USART_InitStructure.USART_WordLength = USART_WordLength_8b;USART_InitStructure.USART_StopBits = USART_StopBits_1;USART_InitStructure.USART_Parity = USART_Parity_No ;USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;USART_Init(USART2, &USART_InitStructure); USART_ITConfig(USART2, USART_IT_TXE, DISABLE); USART_ITConfig(USART2, USART_IT_RXNE, ENABLE);USART_ClearFlag(USART2,USART_FLAG_TC); USART_Cmd(USART2, ENABLE);NVIC_InitStructure.NVIC_IRQChannel = USART2_IRQn;NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1;NVIC_InitStructure.NVIC_IRQChannelSubPriority = 8;NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;NVIC_Init(&NVIC_InitStructure);
}
三、配置USART3
static unsigned char TxBuffer[256];
static unsigned char TxCounter=0;
static unsigned char count=0;
extern void CopeSerial2Data(unsigned char ucData);
void Initial_UART3(unsigned long baudrate)
{GPIO_InitTypeDef GPIO_InitStructure;USART_InitTypeDef USART_InitStructure;NVIC_InitTypeDef NVIC_InitStructure; RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART3 | RCC_APB2Periph_GPIOA, ENABLE);RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB, ENABLE); // GPIOB时钟RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART3,ENABLE);USART_DeInit(USART3);//PB10为TXGPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;GPIO_Init(GPIOB, &GPIO_InitStructure); //PB1为RXGPIO_InitStructure.GPIO_Pin = GPIO_Pin_11;GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;GPIO_Init(GPIOB, &GPIO_InitStructure);USART_InitStructure.USART_BaudRate = baudrate;USART_InitStructure.USART_WordLength = USART_WordLength_8b;USART_InitStructure.USART_StopBits = USART_StopBits_1;USART_InitStructure.USART_Parity = USART_Parity_No ;USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;USART_Init(USART3, &USART_InitStructure); USART_ITConfig(USART3, USART_IT_TXE, DISABLE); USART_ITConfig(USART3, USART_IT_RXNE, ENABLE);USART_ClearFlag(USART3,USART_FLAG_TC); USART_Cmd(USART3, ENABLE);NVIC_InitStructure.NVIC_IRQChannel = USART3_IRQn;NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1;NVIC_InitStructure.NVIC_IRQChannelSubPriority = 8;NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;NVIC_Init(&NVIC_InitStructure);
}
配置大概就是如此，在笔者的程序中，USART1用来STM32连接电脑上串口助手，USART2、3用来连接两个传感器收发数据，有兴趣的读者可以留言或留下邮箱，笔者看到会及时回复
