STM32 USART 使用DMA 详解

前言（绕开吧）：

       这段时间由于我们的项目Manibus板卡需要融入 WIFI， BLT， 网口，CAN，串口的多位一体通讯，互不干扰，而且可以相互调用彼此进行数据通讯，这里为了节省MCU资源，所以就使用DMA的方式来进行串口 和 ESP8266的通讯，接下来就介绍一下具体的操作内容！

        DMA具体的不介绍，总的来说，他就是一个中转站，数据给DMA，他帮你传递或接受，你只要读就行了！！

接下来看代码！

void localUsartDMAConfig(void){

    DMA_InitTypeDef DMA_InitStructure;

    RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1,ENABLE);

  DMA_DeInit(DMA1_Channel4);

  DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)(&USART1->DR);

    DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)USART1_Send_Branch_Buffer;

  DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralDST;

  DMA_InitStructure.DMA_BufferSize = USART1_BUR_MAX;

  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_Circular;

  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_ITConfig(DMA1_Channel4,DMA_IT_TE,ENABLE);

USART_DMACmd(USART1,USART_DMAReq_Tx,ENABLE);

DMA_Cmd(DMA1_Channel4,DISABLE);

  DMA_DeInit(DMA1_Channel5); 

DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)(&USART1->DR);

DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)USART1_Rev_Branch_Buffer;

  DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC;

DMA_InitStructure.DMA_BufferSize = USART1_BUR_MAX;

    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_Circular;

DMA_InitStructure.DMA_Priority =DMA_Priority_High;

DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;

DMA_Init(DMA1_Channel5,&DMA_InitStructure);

DMA_ITConfig(DMA1_Channel5,DMA_IT_TC,ENABLE);

  DMA_ITConfig(DMA1_Channel5,DMA_IT_TE,ENABLE);

    USART_DMACmd(USART1,USART_DMAReq_Rx,ENABLE);

DMA_Cmd(DMA1_Channel5,ENABLE);

}  

这里我们使用的是 USART1, 其对应的DMA 是 TX ->DMA1_Channel4,RX0->DMA1_Channel5, 这里我们还是使用DMA中断，就是DMA_ITConfig(DMA1_Channel4,DMA_IT_TC,ENABLE);

  DMA_ITConfig(DMA1_Channel4,DMA_IT_TE,ENABLE);这样的好处就是，当数据接收满 或者发送完成后，他能自动重新的让其不使能，或者重新更新！

static void NVIC_Configuration(void)

{

NVIC_InitTypeDef NVIC_InitStructure;

//NVIC_PriorityGroupConfig(NVIC_PriorityGroup_1);

NVIC_InitStructure.NVIC_IRQChannel = USART1_IRQn;

NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;

NVIC_InitStructure.NVIC_IRQChannelSubPriority = 2;

NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;

NVIC_Init(&NVIC_InitStructure);

NVIC_InitStructure.NVIC_IRQChannel = DMA1_Channel4_IRQn;

NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;

NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;

NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;

NVIC_Init(&NVIC_InitStructure);

NVIC_InitStructure.NVIC_IRQChannel = DMA1_Channel5_IRQn;

NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;

NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;

NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;

NVIC_Init(&NVIC_InitStructure);

}

这里我们配置NVIC的中断，这里有让DMA有更高的权限，这是为了让他能及时更新！

void localUsartConfig(void)

{

GPIO_InitTypeDef GPIO_InitStructure;

USART_InitTypeDef USART_InitStructure;

RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);

RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1, ENABLE);

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9;

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;

GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

GPIO_Init(GPIOA, &GPIO_InitStructure);

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;

GPIO_Init(GPIOA, &GPIO_InitStructure);

USART_InitStructure.USART_BaudRate = 115200;

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(USART1, &USART_InitStructure);

USART_ITConfig(USART1, USART_IT_IDLE, ENABLE);

USART_Cmd(USART1, ENABLE);

USART_ClearFlag(USART1,USART_FLAG_TC);

localUsartDMAConfig();    //Set DMA 

    NVIC_Configuration();     //Set NVIC

USART1_BASE_HAS_BEEN_INIT_FLAG =1;

}

这里配置 USART1,都是常规操作，这里我们使用的是IDLE空闲中断，就是发送一段字节后，串口空闲 没接受下一个数据了就会中断，也就是一个数据包，（以后都为废话）这样也适合我们的项目要求有关，分总线的通讯方式（分线向执行总线传递数据包）这里就要求不能分线数据交错！

void Usart_ReadArray_(uint8_t *array,u16 length)

{

   if(length){  

length =  length > USART1_BUR_MAX ? 1024: length; 

}else{  

return;

}  

     while(USART1_SendFlag_End ==0);

   if(array)memcpy(USART1_Send_Branch_Buffer,array,length);

DMA_ClearITPendingBit(DMA1_IT_TC4);

   DMA_Cmd(DMA1_Channel4, DISABLE);

   DMA1_Channel4->CNDTR= length;

DMA_Cmd(DMA1_Channel4, ENABLE);

USART1_SendFlag_End = 0;  

}

这里不要被函数名误解，功能就是一个串口通过DMA发送字符串的函数！ 接下来就到重点了，在配置DMA发送函数的时候，我们设置DMA1_Channel4 的使能为DISABLE，是为了不让他一直发送，配置了ENABLE，你会发现它一直发送 00 00.。。。。这也是很好理解的,所以我们在需要的时候让他使能发送！ 函数中有个while是为了让他把已有的数据发送完成，再进行下一个数据包的发送！

void USART1_IRQHandler(void){

u16 data_len;

 if(USART_GetITStatus(USART1,USART_IT_IDLE)!= RESET){

data_len  =USART1->SR;

data_len  =USART1->DR;

DMA_Cmd(DMA1_Channel5,DISABLE);

data_len = USART1_BUR_MAX - DMA_GetCurrDataCounter(DMA1_Channel5);

Usart_ReadArray_(USART1_Rev_Branch_Buffer,data_len);

DMA_ClearFlag(DMA1_FLAG_GL5 | DMA1_FLAG_TC5 | DMA1_FLAG_TE5 | DMA1_FLAG_HT5); 

DMA1_Channel5->CNDTR = USART1_BUR_MAX;

    DMA_Cmd(DMA1_Channel5,ENABLE);

  USART_ClearITPendingBit(USART1, USART_IT_IDLE);

}

}

这里判断时候产生空闲中断！  然后我们需要USART_ReceiveData 这里和先USART1->SR;后USART1->DR; 一样；然后读取数据段长度；这里我进行读取在发送进行验证！ 后面清除各种标志位；然后DMA重装Size, 使能接收DMA，让其继续接收；最后清除空闲中断的标志位！

void DMA1_Channel4_IRQHandler(void){

    DMA_ClearITPendingBit(DMA1_IT_TC4);

  DMA_ClearITPendingBit(DMA1_IT_TE4);

    DMA_Cmd(DMA1_Channel4, DISABLE);

  USART1_SendFlag_End = 1; 

}

void DMA1_Channel5_IRQHandler(void){

  DMA_ClearITPendingBit(DMA1_IT_TC5);

  DMA_ClearITPendingBit(DMA1_IT_TE5);

    DMA_Cmd(DMA1_Channel5, DISABLE); 

    DMA1_Channel5->CNDTR = USART1_BUR_MAX;

  DMA_Cmd(DMA1_Channel5, ENABLE);

}

这里为DMA中断，发送中断是在发送完成后产生的，重新跟新标志位证明发送完成！  接收中断是在接收字节满了后产生的，重装Size!

以上基本结构就配置完成了，有误希望指正！