一.序言

本次实验利用环形队列+DMA空闲中断+串口。。通过这个实验可以非常深入的理解队列，DMA,串口的知识。如果你能自己实现掌握这个实验，那么你应该基本掌握了队列，DMA,串口的知识。

二.实验原理

本次使用的是用环形队列当缓冲器区接收串口数据。我们可以先区了解DMA的空闲中断。本次实验就是使用DMA空闲中断。这里就简单介绍一下，当串口接收到一帧数据后就会产生中断，那么如何判断数据是一帧呢？这里的判断机制就是，如果收到数据后，大概接收一个字节的时间，都没有接收到数据的话，就判断已经接收的数据是一帧。接收一帧数据后，串口就会产生空闲中断。同时DMA会把串口DR移位寄存器的值搬运到环形队列缓冲区。我们只需要在环形队列缓冲器拿数据即可。

三.实战是检验真理的唯一标准

仅仅通过理论，只能说你知道有这个东西，但是你可能并不会。下面我通过代码讲解也帮助深入理解理论。

3.1 usart1.c


void Usart1_Init(void)
{GPIO_InitTypeDef GPIO_InitStructure;USART_InitTypeDef USART_InitStructure;NVIC_InitTypeDef NVIC_InitStructure;DMA_InitTypeDef DMA_InitStructure;RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1|RCC_APB2Periph_GPIOA, ENABLE);	//USART1_TX   GPIOA.9GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9; //PA.9GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;	GPIO_Init(GPIOA, &GPIO_InitStructure);//³õÊ¼»¯GPIOA.9//USART1_RX	  GPIOA.10³õÊ¼»¯GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;//PA10GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;GPIO_Init(GPIOA, &GPIO_InitStructure);////Usart1 NVIC ÅäÖÃNVIC_InitStructure.NVIC_IRQChannel = USART1_IRQn;NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority=5 ;NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;	NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;			NVIC_Init(&NVIC_InitStructure);	//¸ù¾ÝÖ¸¶¨µÄ²ÎÊý³õÊ¼»¯VIC¼Ä´æÆ÷USART_InitStructure.USART_BaudRate = 115200USART_InitStructure.USART_WordLength = USART_WordLength_8bUSART_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); //使能空闲中断USART_ITConfig(USART1, USART_IT_IDLE , ENABLE);//使能发送完成中断--通过串口发送数据USART_ITConfig(USART1, USART_IT_TC , ENABLE);USART_DMACmd(USART1, USART_DMAReq_Tx|USART_DMAReq_Rx, ENABLE);USART_Cmd(USART1, ENABLE);                    RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);		DMA_DeInit(DMA1_Channel5);//外设地址--串口1 的DR寄存器DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)(&USART1->DR);DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)Uart1_Rx_Buffer; DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC; DMA_InitStructure.DMA_BufferSize = BSP_UART1_RX_SIZE; 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_Medium;DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;//串口1的接收引脚为DAM1的通道5DMA_Init(DMA1_Channel5, &DMA_InitStructure)；DMA_Cmd (DMA1_Channel5,ENABLE); //初始化环形队列Fifo_Init(&Uart1_Rx_Fifo,Uart1_Rx_Buffer,BSP_UART1_RX_SIZE);

3.2 串口中断

void USART1_IRQHandler(void)
{ //加上volatile 关键字只是为了防止警告volatile uint32_t temp = 0;BaseType_t xHigherPriorityTaskWoken = pdFALSE;if(USART_GetITStatus(USART1,USART_IT_IDLE)!= RESET)//¿ÕÏÐÖÐ¶Ï{//根据数据量数据入队列//DMA_GetCurrDataCounter(DMA1_Channel5); 通道5还剩下多少个数据应该传输。//初始化的时候设置的通道5传输多少数据。Uart1_Rx_Fifo.in = BSP_UART1_RX_SIZE - DMA_GetCurrDataCounter(DMA1_Channel5);//先读SR 再读DR 只是为了消除空闲中断标志位。手册上有说明temp = USART1->SR; temp = USART1->DR;USART_ClearITPendingBit(USART1,USART_IT_IDLE);}

三.队列代码

代码可能看起来简单，但是不是那么容易理解。得自己慢慢体会，才能真正掌握，
而不是一昧的copy,不然出了问题也解决不了，自己代码水平也不能提高。

4.1 fifo.c

#include "sys.h"
#include "app_fifo.h"//初始化
void Fifo_Init(FIFO_Type* fifo, uint8_t* buffer, uint16_t size)
{fifo->buffer = buffer;fifo->in = 0 ;fifo->out = 0;fifo->size = size;
}
//从队列中拿数据
uint16_t Fifo_Get(FIFO_Type* fifo, uint8_t* buffer, uint16_t len)
{uint16_t lenght;uint16_t in = fifo->in;	uint16_t i;lenght = (in + fifo->size - fifo->out)%fifo->size;if(lenght > len)lenght = len;for(i = 0; i < lenght; i++){buffer[i] = fifo->buffer[(fifo->out + i)%fifo->size];}fifo->out = (fifo->out + lenght)%fifo->size;return lenght;
}

4.2 fifo.h

#ifndef	FIFO_H
#define	FIFO_H
#include "stm32f10x.h"
typedef struct {uint8_t* buffer;	uint16_t in;			uint16_t out;			uint16_t size;		
}FIFO_Type;void Fifo_Init(FIFO_Type* fifo, uint8_t* buffer, uint16_t size);uint16_t Fifo_Get(FIFO_Type* fifo, uint8_t* buffer, uint16_t len);#endif