STM32F407入门学习（2）---USART通信

一、简要介绍

使用过的串口通信方式有RS232和485两种，程序配置方面都稍有不同。

二、代码实例

1. 以USART2为例以RS232方式通讯

   串口初始化

void uart2_init(u32 bound)
{
    GPIO_InitTypeDef GPIO_InitStructure;
    USART_InitTypeDef USART_InitStructure;
    NVIC_InitTypeDef NVIC_InitStructure;

    RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART2, ENABLE);//使能时钟
    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOD, ENABLE);

    GPIO_PinAFConfig(GPIOD,GPIO_PinSource5,GPIO_AF_USART2);
    GPIO_PinAFConfig(GPIOD,GPIO_PinSource6,GPIO_AF_USART2);

    GPIO_InitStructure.GPIO_Pin=GPIO_Pin_5;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_InitStructure.GPIO_Mode=GPIO_Mode_AF;
    GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
    GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
    GPIO_Init(GPIOD, &GPIO_InitStructure);
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
    GPIO_Init(GPIOD, &GPIO_InitStructure);

    USART_InitStructure.USART_BaudRate = bound;//设置波特率
    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_RXNE, ENABLE);  //接收中断
    NVIC_InitStructure.NVIC_IRQChannel = USART2_IRQn;
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 3;
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 3;
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStructure);
    USART_Cmd(USART2, ENABLE);
}

中断服务函数

void USART2_IRQHandler(void)
{   
    if(USART_GetITStatus(USART2,USART_IT_RXNE)!= RESET)
    {
        USART2_Receive(); //接收处理函数
    }
}

发送函数

void Usart_SendChar(USART_TypeDef* USARTx,char dat)
{
    unsigned int i=0;
    while(!USART_GetFlagStatus(USARTx,USART_FLAG_TXE)); 
    USART_SendData(USARTx,dat);
    for(i=0;i<500;i++);
}
//例：发送0x51， Usart_SendChar(USART2, 0x51);

接收函数

void USART2_Receive(void)
{
    USART2_RData = USART_ReceiveData(USART2);
    if(USART2_RxNum<10)
    {
        USART2_RxBuff[USART2_RxNum] = USART2_RData;
        USART2_RxNum++;
    }
    }
    if(USART2_RxNum>9)
    {
        USART2_RxNum=0;
    }   
}

2 . 以USAR4为例以485方式通讯

void uart4_init(u32 bound)
{
    GPIO_InitTypeDef GPIO_InitStructure;
    USART_InitTypeDef USART_InitStructure;
    NVIC_InitTypeDef NVIC_InitStructure;

    RCC_APB1PeriphClockCmd(RCC_APB1Periph_UART4, ENABLE);
    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOC, ENABLE);

    GPIO_PinAFConfig(GPIOC,GPIO_PinSource10,GPIO_AF_UART4);
    GPIO_PinAFConfig(GPIOC,GPIO_PinSource11,GPIO_AF_UART4);

    GPIO_InitStructure.GPIO_Pin=GPIO_Pin_10;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_InitStructure.GPIO_Mode=GPIO_Mode_AF;
    GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
    GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
    GPIO_Init(GPIOC, &GPIO_InitStructure);
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_11;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
    GPIO_Init(GPIOC, &GPIO_InitStructure);
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT;
    GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
    GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(GPIOC, &GPIO_InitStructure);

    USART_InitStructure.USART_BaudRate = bound;
    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(UART4, &USART_InitStructure); 

    USART_ITConfig(UART4, USART_IT_RXNE, ENABLE);
    NVIC_InitStructure.NVIC_IRQChannel = UART4_IRQn;
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 2;
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 3;
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStructure); 
    USART_Cmd(UART4, ENABLE); 
    USART_ClearFlag(UART4, USART_FLAG_TC);                 
}

发送函数

void USART4_SendOpen_Data(void)
{
    u8 i;
    TX4_485;                     
    delay_ms(1);                   
    for(i =0;i <7;i++)
    {   
        USART_SendData(UART4,SendOpen_Buf[i]);
        while(USART_GetFlagStatus(UART4, USART_FLAG_TXE) == RESET);
    }
    delay_ms(1);
    RX4_485;/                  
}

中断服务函数与接收部分同上文USART2中相同。