STM32 DMA笔记

原帖由私奔于2009-01-04 14:30发表:
　　这里有个小小的例子，来演示DMA模块与系统程序并行工作。
　　用串口以低波特率发送一个10K的数据，花费近10s时间，此时按照以往方法，CPU要不断等待数据发送、送数据；或者送数据、进中断、送数据，处理起来比较消耗时间。
　　使用了DMA功能以后，用户程序中只需配置好DMA，开启传输后，再也不需要操心，10K数据完成后会有标志位或中断产生，期间可以做任何想做的事，非常方便。
　　这个是相应的代码例子，基于STM32F103VBT6





#include "stm32f10x_lib.h"
#include "stdio.h"



#define USART1_DR_Base 0x40013804



#define SENDBUFF_SIZE  10240
vu8 SendBuff[SENDBUFF_SIZE];
vu8 RecvBuff[10];
vu8 recv_ptr;


void RCC_Configuration(void);
void GPIO_Configuration(void);
void NVIC_Configuration(void);
void DMA_Configuration(void);
void USART1_Configuration(void);

int fputc(int ch, FILE *f);
void Delay(void);



int main(void)
{
   u16 i;
#ifdef DEBUG
   debug();
#endif
   recv_ptr = 0;
   
   RCC_Configuration();
   GPIO_Configuration();
   NVIC_Configuration();
   DMA_Configuration();
   USART1_Configuration();
   
   printf("\r\nSystem Start...\r\n");
   printf("Initialling SendBuff... \r\n");
   for(i=0;i   {
       SendBuff[i] = i&0xff;
   }
   printf("Initial success!\r\nWaiting for transmission...\r\n");
   //发送去数据已经准备好，按下按键即开始传输
   while(GPIO_ReadInputDataBit(GPIOD, GPIO_Pin_3));
   
   printf("Start DMA transmission!\r\n");
   
   //这里是开始DMA传输前的一些准备工作，将USART1模块设置成DMA方式工作
   USART_DMACmd(USART1, USART_DMAReq_Tx, ENABLE);
   //开始一次DMA传输！
   DMA_Cmd(DMA1_Channel4, ENABLE);
   
   //等待DMA传输完成，此时我们来做另外一些事，点灯
   //实际应用中，传输数据期间，可以执行另外的任务
   while(DMA_GetFlagStatus(DMA1_FLAG_TC4) == RESET)
   {
       LED_1_REV;     //LED翻转
       Delay();       //浪费时间
   }
   //DMA传输结束后，自动关闭了DMA通道，而无需手动关闭
   //下面的语句被注释
   //DMA_Cmd(DMA1_Channel4, DISABLE);
   
   printf("\r\nDMA transmission successful!\r\n");

   
   
   while (1)
   {
   }
}


int fputc(int ch, FILE *f)
{
   //USART_SendData(USART1, (u8) ch);
   USART1->DR = (u8) ch;
   
   
   while(USART_GetFlagStatus(USART1, USART_FLAG_TXE) == RESET)
   {
   }

   return ch;
}


void Delay(void)
{
   u32 i;
   for(i=0;i<0xF0000;i++);
   return;
}


void RCC_Configuration(void)
{
   ErrorStatus HSEStartUpStatus;

   //使能外部晶振
   RCC_HSEConfig(RCC_HSE_ON);
   //等待外部晶振稳定
   HSEStartUpStatus = RCC_WaitForHSEStartUp();
   //如果外部晶振启动成功，则进行下一步操作
   if(HSEStartUpStatus==SUCCESS)
   {
       //设置HCLK（AHB时钟）=SYSCLK
       RCC_HCLKConfig(RCC_SYSCLK_Div1);

       //PCLK1(APB1) = HCLK/2
       RCC_PCLK1Config(RCC_HCLK_Div2);

       //PCLK2(APB2) = HCLK
       RCC_PCLK2Config(RCC_HCLK_Div1);

       //FLASH时序控制
       //推荐值：SYSCLK = 0~24MHz  Latency=0
       //       SYSCLK = 24~48MHz Latency=1
       //       SYSCLK = 48~72MHz Latency=2
       FLASH_SetLatency(FLASH_Latency_2);
       //开启FLASH预取指功能
       FLASH_PrefetchBufferCmd(FLASH_PrefetchBuffer_Enable);

       //PLL设置 SYSCLK/1 * 9 = 8*1*9 = 72MHz
       RCC_PLLConfig(RCC_PLLSource_HSE_Div1, RCC_PLLMul_9);
       //启动PLL
       RCC_PLLCmd(ENABLE);
       //等待PLL稳定
       while(RCC_GetFlagStatus(RCC_FLAG_PLLRDY) == RESET);
       //系统时钟SYSCLK来自PLL输出
       RCC_SYSCLKConfig(RCC_SYSCLKSource_PLLCLK);
       //切换时钟后等待系统时钟稳定
       while(RCC_GetSYSCLKSource()!=0x08);


       
   }

   //下面是给各模块开启时钟
   //启动GPIO
   RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA | RCC_APB2Periph_GPIOB | \
                          RCC_APB2Periph_GPIOC | RCC_APB2Periph_GPIOD,\
                          ENABLE);
   //启动AFIO
   RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO, ENABLE);
   //启动USART1
   RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1, ENABLE);
   //启动DMA时钟
   RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);
   
}




void GPIO_Configuration(void)
{
   GPIO_InitTypeDef GPIO_InitStructure;

   //PC口4567脚设置GPIO输出，推挽 2M
   GPIO_InitStructure.GPIO_Pin = GPIO_Pin_4 | GPIO_Pin_5 | GPIO_Pin_6 | GPIO_Pin_7;
   GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
   GPIO_InitStructure.GPIO_Speed = GPIO_Speed_2MHz;
   GPIO_Init(GPIOC, &GPIO_InitStructure);

   //KEY2 KEY3 JOYKEY
   //位于PD口的3 4 11-15脚，使能设置为输入
   GPIO_InitStructure.GPIO_Pin = GPIO_Pin_3 | GPIO_Pin_4 | GPIO_Pin_11 | GPIO_Pin_12 |\
       GPIO_Pin_13 | GPIO_Pin_14 | GPIO_Pin_15;
   GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
   GPIO_Init(GPIOD, &GPIO_InitStructure);

   //USART1_TX
   GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9;
   GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
   GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
   GPIO_Init(GPIOA, &GPIO_InitStructure);
   
   //USART1_RX
   GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;
   GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
   GPIO_Init(GPIOA, &GPIO_InitStructure);

}




void NVIC_Configuration(void)
{
   NVIC_InitTypeDef NVIC_InitStructure;

#ifdef VECT_TAB_RAM
   // Set the Vector Table base location at 0x20000000
   NVIC_SetVectorTable(NVIC_VectTab_RAM, 0x0);
#else 
   // Set the Vector Table base location at 0x08000000
   NVIC_SetVectorTable(NVIC_VectTab_FLASH, 0x0);
#endif

   //设置NVIC优先级分组为Group2：0-3抢占式优先级，0-3的响应式优先级
   NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2);
   //串口接收中断打开   
   NVIC_InitStructure.NVIC_IRQChannel = USART1_IRQChannel;
   NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
   NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;
   NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
   NVIC_Init(&NVIC_InitStructure);
}



void USART1_Configuration(void)
{
   USART_InitTypeDef USART_InitStructure;
   
   USART_InitStructure.USART_BaudRate = 9600;
   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_Tx | USART_Mode_Rx;
   USART_Init(USART1, &USART_InitStructure);
   
   USART_ITConfig(USART1, USART_IT_RXNE, ENABLE);
   
   USART_Cmd(USART1, ENABLE);
}


void DMA_Configuration(void)
{
   DMA_InitTypeDef DMA_InitStructure;
   //DMA设置：
   //设置DMA源：内存地址&串口数据寄存器地址
   //方向：内存-->外设
   //每次传输位：8bit
   //传输大小DMA_BufferSize=SENDBUFF_SIZE
   //地址自增模式：外设地址不增，内存地址自增1
   //DMA模式：一次传输，非循环
   //优先级：中
   DMA_DeInit(DMA1_Channel4);
   DMA_InitStructure.DMA_PeripheralBaseAddr = USART1_DR_Base;
   DMA_InitStructure.DMA_MemoryBaseAddr = (u32)SendBuff;
   DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralDST;
   DMA_InitStructure.DMA_BufferSize = SENDBUFF_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_Normal;
   DMA_InitStructure.DMA_Priority = DMA_Priority_Medium;
   DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
   DMA_Init(DMA1_Channel4, &DMA_InitStructure);
}