STM32的串口采用DMA方式接收數據測試

主機:WINXP

開發環境:MDK4.23

MCU:STM32F103CBT6

說明:

串口可以配置成用DMA的方式接收數據,不過DMA需要定長才能產生接收中斷,如何接收可變長度的數據呢?

方法有以下3種:

1.將RX腳與一路時鐘外部引腳相連,當串口一幀發完,即可利用此定時器產生超時中斷.這個實時性較高,可以做到1個字節實時監測.

2.不改變硬件,開啟一個定時器監控DMA接收,如果超時則產生中斷.這個實時性不高,因為超時時間必須要大于需要接收幀的時間,精度不好控制.

3.STM32單片機有的串口可以監測總線是否處于空閑,如果空閑則產生中斷.可以用它來監測DMA接收是否完畢.這種方式實時性很高.

本文采用第3種方式.在波特率576000下大數據包沖擊證明可行.

源代碼:

//串口接收DMA緩存#define UART_RX_LEN		128extern uint8_t Uart_Rx[UART_RX_LEN];

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

//---------------------串口功能配置---------------------//打開串口對應的外設時鐘  RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1 , ENABLE); //串口發DMA配置  //啟動DMA時鐘RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);//DMA發送中斷設置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DMA_DeInit(DMA1_Channel4);//外設地址DMA_InitStructure.DMA_PeripheralBaseAddr = (u32)(&USART1->DR);//內存地址DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)Uart_Send_Buffer;//dma傳輸方向單向DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralDST;//設置DMA在傳輸時緩沖區的長度DMA_InitStructure.DMA_BufferSize = 100;//設置DMA的外設遞增模式，一個外設DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;//設置DMA的內存遞增模式DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;//外設數據字長DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;//內存數據字長DMA_InitStructure.DMA_MemoryDataSize = DMA_PeripheralDataSize_Byte;//設置DMA的傳輸模式DMA_InitStructure.DMA_Mode = DMA_Mode_Normal;//設置DMA的優先級別DMA_InitStructure.DMA_Priority = DMA_Priority_High;//設置DMA的2個memory中的變量互相訪問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);//串口收DMA配置  //啟動DMA時鐘RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);//DMA1通道5配置DMA_DeInit(DMA1_Channel5);//外設地址DMA_InitStructure.DMA_PeripheralBaseAddr = (u32)(&USART1->DR);//內存地址DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)Uart_Rx;//dma傳輸方向單向DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC;//設置DMA在傳輸時緩沖區的長度DMA_InitStructure.DMA_BufferSize = UART_RX_LEN;//設置DMA的外設遞增模式，一個外設DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;//設置DMA的內存遞增模式DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;//外設數據字長DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;//內存數據字長DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte;//設置DMA的傳輸模式DMA_InitStructure.DMA_Mode = DMA_Mode_Normal;//設置DMA的優先級別DMA_InitStructure.DMA_Priority = DMA_Priority_VeryHigh;//設置DMA的2個memory中的變量互相訪問DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;DMA_Init(DMA1_Channel5,&DMA_InitStructure);//使能通道5DMA_Cmd(DMA1_Channel5,ENABLE);//初始化參數  //USART_InitStructure.USART_BaudRate = DEFAULT_BAUD;  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);  //TXE發送中斷,TC傳輸完成中斷,RXNE接收中斷,PE奇偶錯誤中斷,可以是多個   //USART_ITConfig(USART1,USART_IT_RXNE,ENABLE);//中斷配置USART_ITConfig(USART1,USART_IT_TC,DISABLE);USART_ITConfig(USART1,USART_IT_RXNE,DISABLE);USART_ITConfig(USART1,USART_IT_IDLE,ENABLE);  //配置UART1中斷  NVIC_PriorityGroupConfig(NVIC_PriorityGroup_3);NVIC_InitStructure.NVIC_IRQChannel = USART1_IRQn;               //通道設置為串口1中斷  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 2;       //中斷占先等級0  NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;              //中斷響應優先級0  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;                 //打開中斷  NVIC_Init(&NVIC_InitStructure);   //采用DMA方式發送USART_DMACmd(USART1,USART_DMAReq_Tx,ENABLE);//采用DMA方式接收USART_DMACmd(USART1,USART_DMAReq_Rx,ENABLE);//啟動串口  USART_Cmd(USART1, ENABLE); 

//串口1接收中斷   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標志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];//啟動串口狀態機usart_state_run(); }//設置傳輸數據長度DMA_SetCurrDataCounter(DMA1_Channel5,UART_RX_LEN);//打開DMADMA_Cmd(DMA1_Channel5,ENABLE);} __nop(); } 

測試結果:

條件:單片機運行于72M,與PC通信速率為460800.PC每隔100ms發送一個9個字節的包:c5 5c 6 0 6F 10 5 4e f7.

測試:單片機每次收到此包,一個IO作電平跳轉,然后處理返回一包.

示波器顯示:

放大顯示: