使用DMA方式发送串口数据

一、初始化部分代码

//串口接收DMA缓存
uint8_t Uart_Rx[UART_RX_LEN] = {};
uint32_t Uart_Send_Buffer[] = {};

void USART1_DMA1_CHANNEL4_Config(void)
{
    GPIO_InitTypeDef GPIO_InitStructure;
    USART_InitTypeDef USART_InitStructure;
    DMA_InitTypeDef DMA_InitStructure;
    NVIC_InitTypeDef NVIC_InitStructure; 

    //---------------------串口功能配置---------------------
    //打开串口对应的外设时钟
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1 , ENABLE);
    //启动DMA时钟
    RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);
    //DMA发送中断设置
    NVIC_InitStructure.NVIC_IRQChannel = DMA1_Channel4_IRQn;
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = ;
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = ;
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStructure);
    //DMA1通道4配置
    DMA_DeInit(DMA1_Channel4);
    //外设地址
    DMA_InitStructure.DMA_PeripheralBaseAddr = (u32)(&USART1->DR);
    //内存地址
    DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)Uart_Send_Buffer;
    //dma传输方向单向
    DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralDST;
    //设置DMA在传输时缓冲区的长度
    DMA_InitStructure.DMA_BufferSize = ;
    //设置DMA的外设递增模式，一个外设
    DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
    //设置DMA的内存递增模式
    DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
    //外设数据字长
    DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;
    //内存数据字长
    DMA_InitStructure.DMA_MemoryDataSize = DMA_PeripheralDataSize_Byte;
    //设置DMA的传输模式
    DMA_InitStructure.DMA_Mode = DMA_Mode_Normal;
    //设置DMA的优先级别
    DMA_InitStructure.DMA_Priority = DMA_Priority_High;
    //设置DMA的2个memory中的变量互相访问
    DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
    DMA_Init(DMA1_Channel4,&DMA_InitStructure);
    DMA_ITConfig(DMA1_Channel4,DMA_IT_TC,ENABLE);

    //使能通道4
    //DMA_Cmd(DMA1_Channel4, ENABLE);

    //设置IO口时钟
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA | RCC_APB2Periph_AFIO, ENABLE);
    //串口1的管脚初始化---------------------------------------------
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9;                       //管脚9
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_2MHz;                //选择GPIO响应速度
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;                 //复用推挽输出
    GPIO_Init(GPIOA, &GPIO_InitStructure);                          //TX初始化
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;                      //管脚10
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_2MHz;                //选择GPIO响应速度
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;           //浮空输入
    GPIO_Init(GPIOA, &GPIO_InitStructure);                          //RX初始化  

    //初始化参数----------------------------------------------------
    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 = ;
    //初始化串口
    USART_Init(USART1,&USART_InitStructure);
    //TXE发送中断,TC传输完成中断,RXNE接收中断,PE奇偶错误中断,可以是多个
    USART_ITConfig(USART1,USART_IT_RXNE,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 = ;       //中断占先等级0
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = ;              //中断响应优先级0
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;                 //打开中断
    NVIC_Init(&NVIC_InitStructure);                                 //初始化  

    //采用DMA方式发送
    USART_DMACmd(USART1,USART_DMAReq_Tx,ENABLE);
    //启动串口
    USART_Cmd(USART1, ENABLE);
}

串口初始化后要连上DMA通道。DMA的通道在参考手册里有对应的表格DMA1和DMA2。

    DMA_Cmd(DMA1_Channel4, ENABLE); 

运行一次，后如果是DMA_Mode_Normal就进中断。所以准备好数据后，就可以开启DMA命令，就会自动发送。

二、DMA中断函数

void DMA1_Channel4_IRQHandler(void)
{
    if(DMA_GetFlagStatus(DMA1_FLAG_TC4)==SET)
    {
        DMA_Cmd (DMA1_Channel4,DISABLE);//关闭DMA通道
        DMA_ClearFlag(DMA1_FLAG_TC4);//清中断标志，否则会一直中断
//        DMA_SetCurrDataCounter(DMA1_Channel4, 2);//重置传输数目，当再次达到这个数目就会进中断
//        DMA_Cmd(DMA1_Channel4,ENABLE);//开启DMA通道
    }
}

中断函数需要清除中断。

启动发送函数，size是char数据长度

void DMA1_Channel4_Send(uint32_t *buff, uint16_t size)
{
    uint16_t i;
    for(i=;i<size;i++) {
        Uart_Send_Buffer[i] = buff[i];
    }

    DMA_SetCurrDataCounter(DMA1_Channel4, size);
    DMA_Cmd(DMA1_Channel4, ENABLE);
}