單片機(jī)DMA驅(qū)動(dòng)串口過程

先上代碼：

#define COMM_COM                  USART2
#define COMM_COM_CLK              RCC_APB1Periph_USART2
#define COMM_COM_TX_GPIO_CLK      RCC_AHB1Periph_GPIOD     //UART TX
#define COMM_COM_TX_PIN           GPIO_Pin_5
#define COMM_COM_TX_GPIO_PORT     GPIOD
#define COMM_COM_TX_SOURCE        GPIO_PinSource5
#define COMM_COM_TX_AF            GPIO_AF_USART2
#define COMM_COM_RX_GPIO_CLK      RCC_AHB1Periph_GPIOD     //UART RX
#define COMM_COM_RX_PIN           GPIO_Pin_6
#define COMM_COM_RX_GPIO_PORT     GPIOD
#define COMM_COM_RX_SOURCE        GPIO_PinSource6
#define COMM_COM_RX_AF            GPIO_AF_USART2
#define COMM_COM_IRQn             USART2_IRQn
#define COMM_COM_Priority         9                        //優(yōu)先級(jí)
#define COMM_COM_BaudRate         115200                   //波特率
#define COMM_COM_IRQHandler       USART2_IRQHandler        //中斷函數(shù)接口(見stm32f4xx_it.c)


USART配置：



/************************************************
函數(shù)名稱 ：USART_COMM_Configuration
功    能 ：通信串口配置
參    數(shù) ：無
返 回 值 ：無
作    者 ：strongerHuang
*************************************************/
void USART_COMM_Configuration(void)
{
  GPIO_InitTypeDef  GPIO_InitStructure;
  USART_InitTypeDef USART_InitStructure;
  NVIC_InitTypeDef  NVIC_InitStructure;  

  /* 時(shí)鐘配置 */
  RCC_AHB1PeriphClockCmd(COMM_COM_TX_GPIO_CLK | COMM_COM_RX_GPIO_CLK, ENABLE);  
  if((USART1 == COMM_COM) || (USART6 == COMM_COM))
    RCC_APB2PeriphClockCmd(COMM_COM_CLK, ENABLE);
  else
    RCC_APB1PeriphClockCmd(COMM_COM_CLK, ENABLE);  

  /* 復(fù)用配置 */
  GPIO_PinAFConfig(COMM_COM_TX_GPIO_PORT, COMM_COM_TX_SOURCE, COMM_COM_TX_AF);
  GPIO_PinAFConfig(COMM_COM_RX_GPIO_PORT, COMM_COM_RX_SOURCE, COMM_COM_RX_AF);  

  /* 引腳配置 */
  GPIO_InitStructure.GPIO_Pin = COMM_COM_TX_PIN;                     //USART Tx
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;                       //復(fù)用模式
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
  GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
  GPIO_Init(COMM_COM_TX_GPIO_PORT, &GPIO_InitStructure);

  GPIO_InitStructure.GPIO_Pin = COMM_COM_RX_PIN;                     //USART Rx
  GPIO_Init(COMM_COM_RX_GPIO_PORT, &GPIO_InitStructure);  

  /* NVIC配置 */
  NVIC_InitStructure.NVIC_IRQChannel = COMM_COM_IRQn;
  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = COMM_COM_Priority;
  NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
  NVIC_Init(&NVIC_InitStructure);  

  /* USART配置 */
  USART_InitStructure.USART_BaudRate = COMM_COM_BaudRate;            //波特率
  USART_InitStructure.USART_WordLength = USART_WordLength_8b;        //傳輸位數(shù)
  USART_InitStructure.USART_StopBits = USART_StopBits_1;             //停止位
  USART_InitStructure.USART_Parity = USART_Parity_No ;               //校驗(yàn)位
  USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
  USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;    //收發(fā)功能
  USART_Init(COMM_COM, &USART_InitStructure);

  USART_ClearFlag(COMM_COM, USART_FLAG_RXNE | USART_FLAG_TC);
  USART_ITConfig(COMM_COM, USART_IT_RXNE, ENABLE);                   //接收中斷

  USART_DMACmd(COMM_COM, USART_DMAReq_Tx, ENABLE);                   //使能DMA

  USART_Cmd(COMM_COM, ENABLE);                                       //使能USART
}

DMA配置中的宏定義：

#define COMM_DR_ADDRESS           ((uint32_t)USART2 + 0x04)
#define COMM_DMA                  DMA1
#define COMM_DMA_CLK              RCC_AHB1Periph_DMA1
#define COMM_TX_DMA_CHANNEL       DMA_Channel_4
#define COMM_TX_DMA_STREAM        DMA1_Stream6
#define COMM_TX_DMA_FLAG_TCIF     DMA_FLAG_TCIF6
#define COMM_TX_DMA_IRQn          DMA1_Stream6_IRQn
#define COMM_TX_DMA_Priority      8                        //優(yōu)先級(jí)
#define COMM_TX_DMA_IRQHandler    DMA1_Stream6_IRQHandler  //中斷函數(shù)接口(見stm32f4xx_it.c)
#define COMM_TX_DMA_IT_TCIF       DMA_IT_TCIF6

通訊串口的配置

/************************************************
函數(shù)名稱 ：USART_COMM_DMA_Configuration
功    能 ：通信串口的DMA配置
參    數(shù) ：無
返 回 值 ：無
作    者 ：strongerHuang
*************************************************/
void USART_COMM_DMA_Configuration(void)
{
  DMA_InitTypeDef DMA_InitStructure;
  NVIC_InitTypeDef NVIC_InitStructure;  

  /* 使能時(shí)鐘 */
  RCC_AHB1PeriphClockCmd(COMM_DMA_CLK, ENABLE);  

  /* NVIC配置 */
  NVIC_InitStructure.NVIC_IRQChannel = COMM_TX_DMA_IRQn;
  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = COMM_TX_DMA_Priority;
  NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
  NVIC_Init(&NVIC_InitStructure);  

  /* DMA配置 */
  DMA_DeInit(COMM_TX_DMA_STREAM);
  DMA_InitStructure.DMA_Channel = COMM_TX_DMA_CHANNEL;               //DMA通道
  DMA_InitStructure.DMA_PeripheralBaseAddr = COMM_DR_ADDRESS;        //外設(shè)地址
  DMA_InitStructure.DMA_Memory0BaseAddr = (uint32_t)0;               //內(nèi)存地址(待傳入參數(shù))
  DMA_InitStructure.DMA_DIR = DMA_DIR_MemoryToPeripheral;            //傳輸方向
  DMA_InitStructure.DMA_BufferSize = 0;                              //傳輸長(zhǎng)度(待傳入?yún)?shù))
  DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;   //外設(shè)遞增
  DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;            //內(nèi)存遞增
  DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;
  DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte;    //數(shù)據(jù)寬度
  DMA_InitStructure.DMA_Mode = DMA_Mode_Normal;                      //循環(huán)模式
  DMA_InitStructure.DMA_Priority = DMA_Priority_Medium;              //優(yōu)先級(jí)
  DMA_InitStructure.DMA_FIFOMode = DMA_FIFOMode_Disable;
  DMA_InitStructure.DMA_FIFOThreshold = DMA_FIFOThreshold_HalfFull;
  DMA_InitStructure.DMA_MemoryBurst = DMA_MemoryBurst_Single;
  DMA_InitStructure.DMA_PeripheralBurst = DMA_PeripheralBurst_Single;
  DMA_Init(COMM_TX_DMA_STREAM, &DMA_InitStructure);

  DMA_ClearFlag(COMM_TX_DMA_STREAM, COMM_TX_DMA_FLAG_TCIF);
  DMA_ITConfig(COMM_TX_DMA_STREAM, DMA_IT_TC, ENABLE);               //使能DMA傳輸完成中斷

  DMA_Cmd(COMM_TX_DMA_STREAM, DISABLE);                              //初始化禁止
}

j接下來實(shí)現(xiàn)數(shù)據(jù)發(fā)送與接收

/************************************************
函數(shù)名稱 ：COMM_SendBufByDMA
功    能 ：通信串口通過DMA發(fā)送數(shù)據(jù)
參    數(shù) ：Buf ------ 數(shù)據(jù)(地址)
            Length --- 數(shù)據(jù)長(zhǎng)度(字節(jié))
返 回 值 ：無
作    者 ：strongerHuang
*************************************************/
void COMM_SendBufByDMA(uint8_t *Buf, uint16_t Length)
{
  DMA_Cmd(COMM_TX_DMA_STREAM, DISABLE);                              //關(guān)閉DMA
                                                                     //內(nèi)存地址
  DMA_MemoryTargetConfig(COMM_TX_DMA_STREAM, (uint32_t)Buf, DMA_Memory_0);
  DMA_SetCurrDataCounter(COMM_TX_DMA_STREAM, Length);                //設(shè)置DMA傳輸長(zhǎng)度
  DMA_Cmd(COMM_TX_DMA_STREAM, ENABLE);                               //使能DMA
}

DMA是一種在嵌入式實(shí)時(shí)任務(wù)處理中常用的功能。

而UART發(fā)送數(shù)據(jù)包，使用DMA方式能大量減輕CPU處理的時(shí)間，使其CPU資源不被大量浪費(fèi)，尤其在UART收發(fā)大量數(shù)據(jù)包（如高頻率收發(fā)指令）時(shí)具有明顯優(yōu)勢(shì)。

審核編輯：湯梓紅