ADC with DMA

DMA stands for direct memory access, this can be used one data needed to be transferred from place to another as it is for example from RAM to FLASH memory, from I2C, SPI or ADC to memory.
The DMA controller replaces the CPU in data transfer operation so the CPU can be freed to do other tasks.
DMA can be useful when there is critical data to receive and the user wants to see all data, even using the interrupt I/O there still time wasted while context switching, this can be elure with DMA.
The STM32 microcontroller has 2 DMA Controllers (DMA1, DMA2) and there are connected to the peripheral and memory through channels.
In the following example, I will illustrate the use of DMA with ADC.

#include "stm32f4xx.h"
#include "stm32f4xx_rcc.h"
#include "stm32f4xx_gpio.h"
#include "stm32f4xx_adc.h"
#include "stm32f4xx_dma.h"


#define ADC3_DR_ADDRESS    ((uint32_t)0x4001224C)

/* Private macro -------------------------------------------------------------*/
/* Private variables ---------------------------------------------------------*/
__IO uint32_t ADC3ConvertedValue = 0;
void config(){
 ADC_InitTypeDef       ADC_InitStructure;
   ADC_CommonInitTypeDef ADC_CommonInitStructure;
   DMA_InitTypeDef       DMA_InitStructure;
   GPIO_InitTypeDef      GPIO_InitStructure;

   /* Enable ADC3, DMA2 and GPIO clocks ****************************************/
   RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_DMA2 | RCC_AHB1Periph_GPIOC, ENABLE);
   RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC3, ENABLE);

   /* DMA2 Stream0 channel2 configuration **************************************/
   DMA_InitStructure.DMA_Channel = DMA_Channel_2;
   DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)ADC3_DR_ADDRESS;
   DMA_InitStructure.DMA_Memory0BaseAddr = (uint32_t)&ADC3ConvertedValue;
   DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralToMemory;
   DMA_InitStructure.DMA_BufferSize = 1;
   DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
   DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Disable;
   DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_HalfWord;
   DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_HalfWord;
   DMA_InitStructure.DMA_Mode = DMA_Mode_Circular;
   DMA_InitStructure.DMA_Priority = DMA_Priority_High;
   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);

   /* Configure ADC3 Channel7 pin as analog input ******************************/
   GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0;
   GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AN;
   GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL ;
   GPIO_Init(GPIOC, &GPIO_InitStructure);

   /* ADC Common Init **********************************************************/
   ADC_CommonInitStructure.ADC_Mode = ADC_Mode_Independent;
   ADC_CommonInitStructure.ADC_Prescaler = ADC_Prescaler_Div2;
   ADC_CommonInitStructure.ADC_DMAAccessMode = ADC_DMAAccessMode_Disabled;
   ADC_CommonInitStructure.ADC_TwoSamplingDelay = ADC_TwoSamplingDelay_5Cycles;
   ADC_CommonInit(&ADC_CommonInitStructure);

   /* ADC3 Init ****************************************************************/
   ADC_InitStructure.ADC_Resolution = ADC_Resolution_12b;
   ADC_InitStructure.ADC_ScanConvMode = DISABLE;
   ADC_InitStructure.ADC_ContinuousConvMode = ENABLE;
   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;
   ADC_Init(ADC3, &ADC_InitStructure);

   /* ADC3 regular channel7 configuration *************************************/
   ADC_RegularChannelConfig(ADC3, ADC_Channel_10, 1, ADC_SampleTime_3Cycles);

  /* Enable DMA request after last transfer (Single-ADC mode) */
   ADC_DMARequestAfterLastTransferCmd(ADC3, ENABLE);

   /* Enable ADC3 DMA */
   ADC_DMACmd(ADC3, ENABLE);

   /* Enable ADC3 */
   ADC_Cmd(ADC3, ENABLE);

}
int main(void)
{
 config();
 ADC_SoftwareStartConv(ADC3);
    while(1)
    {
    }
}