STM32的串口采用DMA方式接收数据测试

主机:WINXP

开发环境:MDK4.23

MCU:STM32F103CBT6

说明:

串口可以配置成用DMA的方式接收数据,不过DMA需要定长才能产生接收中断,如何接收可变长度的数据呢?

方法有以下3种:

1.将RX脚与一路时钟外部引脚相连,当串口一帧发完,即可利用此定时器产生超时中断.这个实时性较高,可以做到1个字节实时监测.

2.不改变硬件,开启一个定时器监控DMA接收,如果超时则产生中断.这个实时性不高,因为超时时间必须要大于需要接收帧的时间,精度不好控制.

3.STM32单片机有的串口可以监测总线是否处于空闲,如果空闲则产生中断.可以用它来监测DMA接收是否完毕.这种方式实时性很高.

本文采用第3种方式.在波特率576000下大数据包冲击证明可行.

源代码:

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

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

//---------------------串口功能配置---------------------
	//打开串口对应的外设时钟  
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1 , ENABLE); 
	//串口发DMA配置  
	//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 = 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 = 100;
	//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);

	//串口收DMA配置  
	//启动DMA时钟
    RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);
	//DMA1通道5配置
	DMA_DeInit(DMA1_Channel5);
	//外设地址
	DMA_InitStructure.DMA_PeripheralBaseAddr = (u32)(&USART1->DR);
	//内存地址
	DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)Uart_Rx;
	//dma传输方向单向
	DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC;
	//设置DMA在传输时缓冲区的长度
	DMA_InitStructure.DMA_BufferSize = UART_RX_LEN;
	//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_MemoryDataSize_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_VeryHigh;
	//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_Channel5,&DMA_InitStructure);

	//使能通道5
	DMA_Cmd(DMA1_Channel5,ENABLE);
	
	  
    //初始化参数  
    //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);
	
	//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);   
        
	//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); 

//串口1接收中断   
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];
		  	//启动串口状态机
			usart_state_run(); 
		}

		//设置传输数据长度
		DMA_SetCurrDataCounter(DMA1_Channel5,UART_RX_LEN);
    	//打开DMA
		DMA_Cmd(DMA1_Channel5,ENABLE);
    } 
	
	__nop(); 
} 

测试结果:

条件:单片机运行于72M,与PC通信速率为460800.PC每隔100ms发送一个9个字节的包:c5 5c 6 0 6F 10 5 4e f7.

测试:单片机每次收到此包,一个IO作电平跳转,然后处理返回一包.

示波器显示:

放大显示: