STM32——采用DMA的方式实现串口收发数据

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概述

想必看到这篇博客的你已经知道了DMA的好处了吧，所以这儿就不过多地讲述DMA对于缓解MCU压力有多么重要的用途，DMA在很多方面都可以使用，如IIC，SPI，USART等，这儿主要给出DMA在USART上面的一个实例。

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代码实现

主要代码直接在一个程序中实现

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全局变量以及宏定义

#define DEFAULT_BAUD 115200
#define UART_RX_LEN        128

/*串口接收DMA缓存*/
uint8_t Uart_Rx[UART_RX_LEN] = {0};

/*串口发送DMA缓存*/
uint8_t Uart_Send_Buffer[100]={0};

uint8_t Data_Receive_Usart=0;

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DMA和USART的初始化的函数

void usart_dma_init(void)
{
    GPIO_InitTypeDef    GPIO_InitStructure;
    USART_InitTypeDef    USART_InitStructure;
    DMA_InitTypeDef        DMA_InitStructure;
    NVIC_InitTypeDef    NVIC_InitStructure;



    /*  配置GPIO的模式和IO口 */    
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA,ENABLE);  
    GPIO_InitStructure.GPIO_Pin=GPIO_Pin_9;                    //TX
    GPIO_InitStructure.GPIO_Speed=GPIO_Speed_50MHz;
    GPIO_InitStructure.GPIO_Mode=GPIO_Mode_AF_PP;            //复用推挽输出
    GPIO_Init(GPIOA,&GPIO_InitStructure);                    //初始化串口输入IO
    GPIO_InitStructure.GPIO_Pin=GPIO_Pin_10;                //RX
    GPIO_InitStructure.GPIO_Mode=GPIO_Mode_IN_FLOATING;        //模拟输入
    GPIO_Init(GPIOA,&GPIO_InitStructure);     



    /*初始化串口接收和发送函数*/
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1 , ENABLE);
    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_InitStructure.USART_BaudRate = DEFAULT_BAUD; 

    /*初始化串口*/
    USART_Init(USART1,&USART_InitStructure);

    /*中断配置*/
    USART_ITConfig(USART1,USART_IT_TC,DISABLE);
    USART_ITConfig(USART1,USART_IT_RXNE,DISABLE);
    USART_ITConfig(USART1,USART_IT_IDLE,ENABLE); 

    //配置UART1中断  
    NVIC_PriorityGroupConfig(NVIC_PriorityGroup_3);
    NVIC_InitStructure.NVIC_IRQChannel = USART1_IRQn;              //通道设置为串口1中断  
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 2;      //中断占先等级0  
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;             //中断响应优先级0  
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;                //打开中断  
    NVIC_Init(&NVIC_InitStructure);



    /*DMA发送中断设置*/
    NVIC_InitStructure.NVIC_IRQChannel = DMA1_Channel4_IRQn;
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 3;
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 2;
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStructure);


    /*DMA1通道4配置发送*/
    RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);
    DMA_DeInit(DMA1_Channel4);
    DMA_InitStructure.DMA_PeripheralBaseAddr = (u32)(&USART1->DR);
    DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)Uart_Send_Buffer;
    DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralDST;
    DMA_InitStructure.DMA_BufferSize = 100;
    DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
    DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
    DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;
    DMA_InitStructure.DMA_MemoryDataSize = DMA_PeripheralDataSize_Byte;
    DMA_InitStructure.DMA_Mode = DMA_Mode_Normal;
    DMA_InitStructure.DMA_Priority = DMA_Priority_High;
    DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
    DMA_Init(DMA1_Channel4,&DMA_InitStructure);
    DMA_ITConfig(DMA1_Channel4,DMA_IT_TC,ENABLE);
    //DMA_Cmd(DMA1_Channel4, ENABLE);//使能通道4，一般发送的时候再使能



    /*DMA1通道5配置接收*/
    RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);
    DMA_DeInit(DMA1_Channel5);
    DMA_InitStructure.DMA_PeripheralBaseAddr = (u32)(&USART1->DR);
    DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)Uart_Rx;
    DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC;
    DMA_InitStructure.DMA_BufferSize = UART_RX_LEN;
    DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
    DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
    DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;
    DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte;
    DMA_InitStructure.DMA_Mode = DMA_Mode_Normal;
    DMA_InitStructure.DMA_Priority = DMA_Priority_VeryHigh;
    DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
    DMA_Init(DMA1_Channel5,&DMA_InitStructure);

    /*使能通道5*/
    DMA_Cmd(DMA1_Channel5,ENABLE);



    //采用DMA方式发送
    USART_DMACmd(USART1,USART_DMAReq_Tx,ENABLE);

    //采用DMA方式接收
    USART_DMACmd(USART1,USART_DMAReq_Rx,ENABLE);

    //启动串口  
    USART_Cmd(USART1, ENABLE);
}

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DMA发送使能函数

/**@ brief 使能发送数据
 *
 * 启动DMA数据发送功能
 * 
 * @param size表示需要发送的DMA中数据的个数
 */
void uart_dma_send_enable(uint16_t size)
{
    DMA1_Channel4->CNDTR = (uint16_t)size; 
    DMA_Cmd(DMA1_Channel4, ENABLE);       
}    

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串口接收的中断函数

/**@ brief串口1接收中断
 *
 * 收到一帧数据进入一次，进行DMA的读取
 * 
 */
void USART1_IRQHandler(void)                               
{   
    uint32_t temp = 0;
    uint16_t i = 0;

    if(USART_GetITStatus(USART1, USART_IT_IDLE) != RESET)
    {
        //USART_ClearFlag(USART1,USART_IT_IDLE);
        temp = USART1->SR;
        temp = USART1->DR; //清USART_IT_IDLE标志

        DMA_Cmd(DMA1_Channel5,DISABLE);

        temp = UART_RX_LEN - DMA_GetCurrDataCounter(DMA1_Channel5);
        for (i = 0;i < temp;i++)
        {
            Data_Receive_Usart = Uart_Rx[i];

            //+++对收到的数据加一后回发出去        
            Uart_Send_Buffer[i]=Data_Receive_Usart+1;                        
            uart_dma_send_enable(temp);
            //+++            
        }

        //设置传输数据长度
        DMA_SetCurrDataCounter(DMA1_Channel5,UART_RX_LEN);

        //打开DMA
        DMA_Cmd(DMA1_Channel5,ENABLE);
    } 
} 

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DMA发送中断

/**@ brief DMA发送中断
 *
 * 发送数据，将DMA中的数据发送出去
 * 
 */
void DMA1_Channel4_IRQHandler(void)
{
    if(DMA_GetITStatus(DMA1_FLAG_TC4)==SET)
    {
        DMA_ClearFlag(DMA1_FLAG_GL4);        
        DMA_Cmd(DMA1_Channel4, DISABLE);  
    }
}

到此为止主要代码就已经结束了，基本上能够满足测试要求

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项目工程下载

串口1的DMA实现 点击下载

串口2的DMA实现 点击下载

串口3的DMA实现 点击下载