stm32f4 adc dual model with dma

hello everyone,

Now I use stm32f4 discovery. I want to use ADC example ''ADC_DualModeRegulSimu'' from the StdPeriph_Lib_V1.1.0 Project.

I have following questions:

1. They use ADC Dual Mode with DMA, but they don't active ADC_DMA(ADC1, enable);

2. In ADCx_CH10_CH11_Config() they selected 

  ADC_InitStructure.ADC_ExternalTrigConv = ADC_ExternalTrigConv_T1_CC1;

I don't know why is it? They used softwarestart of ADC, otherwise they don't active the trigger edge.

3. in DMA_Config() 

    DMA_InitStructure.DMA_Channel = DMA_Channel_0; 

  DMA_InitStructure.DMA_Memory0BaseAddr = (uint32_t)&aADCDualConvertedValue;

  DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)ADC_

CCR

_ADDRESS;

  DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralToMemory;

  DMA_InitStructure.DMA_BufferSize = 4;

  DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;

  DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;

  DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_

HalfWord

;

  DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_

HalfWord

;

I think ADC_CCR should be CDR.

 But in Dual Mode high 16 Bits of CDR save ADC2 data and low 16 Bits save ADC1 data. DMA_PeripheralDataSize should be defined as Word (32Bits) or I didn't really understand the data transfer between ADC_CDR and DMA_Memory. CDR send data of CH10 (ADC1), CH11(ADC2), CH11(ADC1), CH12(ADC2) in this example, the data in CDR has to be sent two times?

(CDR(15:0) then CDR(31:16)?).

Thank you very much for your attention and hope your answer!