stm32之30.DMA-编程知识

stm32之30.DMA

DMA（硬件加速方法）一般用于帮运比较大的数据（如：摄像头数据图像传输），寄存器-》DMA-》RAM 或者 RAM-》DMA-》寄存器提高CPU的工作效率

源码--

#include "myhead.h"
#include "adc.h"#include "delay.h"#include "usart.h"
extern u16 ADC1_Value;u16 ADC1_Value;void DMA_init(void)
{GPIO_InitTypeDef   GPIO_InitStructure;ADC_InitTypeDef       ADC_InitStructure;ADC_CommonInitTypeDef ADC_CommonInitStructure;DMA_InitTypeDef       DMA_InitStructure;//1.时钟使能ADC1 GPIOARCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);//1分频RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC1, ENABLE);//2分频RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_DMA2, ENABLE);//1分频//DMA2初始化DMA_InitStructure.DMA_Channel =  DMA_Channel_0;  //通道0DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)&(ADC1->DR); //搬运的起始地址DMA_InitStructure.DMA_Memory0BaseAddr = (uint32_t)&ADC1_Value; //搬运的目的地址DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralToMemory;   //DMA搬运的方向DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_HalfWord;   //设置搬运起始点到目的地发数据宽度DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_HalfWord;   //字节大小  半个字节DMA_InitStructure.DMA_BufferSize = 1;    //设置缓存块数DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable; //设置地址自动递增  DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Disable;   DMA_InitStructure.DMA_Mode = DMA_Mode_Circular;     //DMA搬运模式 Nomal Circular循环DMA_InitStructure.DMA_Priority = DMA_Priority_High;   //触发优先级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(DMA2_Stream0, &DMA_InitStructure);DMA_Cmd(DMA2_Stream0, ENABLE);  //使能DMAGPIO_InitStructure.GPIO_Pin = GPIO_Pin_5;GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AN;GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL ;//不需要上下拉电阻GPIO_Init(GPIOA, &GPIO_InitStructure);//3.ADC的公共部分配置ADC_CommonInitStructure.ADC_Mode = ADC_Mode_Independent;//独立模式，双重模式，三重模式ADC_CommonInitStructure.ADC_Prescaler = ADC_Prescaler_Div4;  //84MHZ---/4 给到具体ADC  21MHZ<=36MHZADC_CommonInitStructure.ADC_DMAAccessMode = ADC_DMAAccessMode_Disabled;  //多重ADC模式有关，一般独立ADC都不需要开启ADC_CommonInitStructure.ADC_TwoSamplingDelay = ADC_TwoSamplingDelay_5Cycles;//多重ADC模式的采样间隔ADC_CommonInit(&ADC_CommonInitStructure);//4.指定ADC配置ADC_InitStructure.ADC_Resolution = ADC_Resolution_12b;  //精度选择ADC_InitStructure.ADC_ScanConvMode = DISABLE;           //扫描模式选择   开扫描/关扫描    单个ADC开了多个通道才要扫描模式ADC_InitStructure.ADC_ContinuousConvMode = ENABLE;      //连续转换模式  开/关ADC_InitStructure.ADC_ExternalTrigConvEdge = ADC_ExternalTrigConvEdge_None;    //ADC_InitStructure.ADC_ExternalTrigConv = ADC_ExternalTrigConv_T1_CC1;ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Right;ADC_InitStructure.ADC_NbrOfConversion = 1;   //待转换的通道数量    如果adc通道开多个（adc1，adc3），通道数量跟数量一样多，上面扫描模式就得开ADC_Init(ADC1, &ADC_InitStructure);/* Enable DMA request after last transfer (Single-ADC mode) */  //ADC1->CR2  第9bit DDS位  中文手册276页ADC_DMARequestAfterLastTransferCmd(ADC1, ENABLE);/* Enable ADC3 DMA *///ADC1->CR2  第8bit DMA位  中文手册276页ADC_DMACmd(ADC1, ENABLE);//5.通道规则设置--设置adc通道的转换顺序ADC_RegularChannelConfig(ADC1, ADC_Channel_5, 1, ADC_SampleTime_3Cycles);//ADC_SampleTime_3Cycles通道转换速度，等级越高转换速度越快//6.使能ADC模块ADC_Cmd(ADC1,ENABLE);
}int main(void)
{adc_init();usart1_init(9600);DMA_init();ADC_SoftwareStartConv(ADC1);   //ADC通道配置必须放DMA_init/adc_init()后面while(1){//3.3v/4096 =xV/ADC1->DRprintf("%.2fv\r\n",ADC1_Value*3.3/4095);  //不断读取ADC1的转换结果  转换成电压值  (.2f表示double类型小数点后两位打印结果）delay_ms(1000);}}