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
![](https://img.laitimes.com/img/9ZDMuAjOiMmIsIjOiQnIsIyZuBnLxY2M1MjYmFTZwUmN5kTN5kDOjRTYkNDNlhTO0IWY0UzLc52YucWbp5GZzNmLn9Gbi1yZtl2Lc9CX6MHc0RHaiojIsJye.png)
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.9
GPIO_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.10
GPIO_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TX
GPIO_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TX
GPIO_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RX
GPIO_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