ADC1和TIM1的配置如下，ADC为啥启动不了呢， ADC1ConvertedValue 的值一直是0

void _ADC1_CH2_DMA_Config(void) {  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_GPIOA, ENABLE);  RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC1, ENABLE);

 /* DMA2 Stream0 channel2 configuration **************************************/  DMA_InitStructure.DMA_Channel = DMA_Channel_0;   DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)ADC1_DR_ADDRESS;  DMA_InitStructure.DMA_Memory0BaseAddr = (uint32_t)&ADC1ConvertedValue;//(uint32_t)&ADC1ConvertedValue;  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_Enable;//DMA_MemoryInc_Disable;  DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_HalfWord;  DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_HalfWord;  DMA_InitStructure.DMA_Mode = DMA_Mode_Normal;//DMA_Mode_Circular;  DMA_InitStructure.DMA_Priority = DMA_Priority_VeryHigh;  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 ADC1 Channel2 pin as analog input ******************************/  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2;  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AN;  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL ;  GPIO_Init(GPIOA, &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);

 /* ADC1 Init ****************************************************************/  ADC_InitStructure.ADC_Resolution = ADC_Resolution_8b;  ADC_InitStructure.ADC_ScanConvMode = DISABLE;//ENABLE;  ADC_InitStructure.ADC_ContinuousConvMode = DISABLE;//ENABLE;  ADC_InitStructure.ADC_ExternalTrigConvEdge = ADC_ExternalTrigConvEdge_Rising;  ADC_InitStructure.ADC_ExternalTrigConv = ADC_ExternalTrigConv_T1_CC1;  ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Right;  ADC_InitStructure.ADC_NbrOfConversion = 1;  ADC_Init(ADC1, &ADC_InitStructure);

 /* ADC1 regular channel2 configuration *************************************/  ADC_RegularChannelConfig(ADC1, ADC_Channel_2, 1, ADC_SampleTime_3Cycles);  /* Enable DMA request after last transfer (Single-ADC mode) */   ADC_DMARequestAfterLastTransferCmd(ADC1, ENABLE);  /* Enable ADC1 DMA */  ADC_DMACmd(ADC1, ENABLE);  /* Enable ADC1 */  ADC_Cmd(ADC1, ENABLE);    ADC_SoftwareStartConv(ADC1);
} void TIM_Config(void) {  TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;  TIM_OCInitTypeDef  TIM_OCInitStructure;  RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM1, ENABLE);  /* Time Base configuration */  TIM_TimeBaseStructure.TIM_Prescaler = 8-1;  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;  TIM_TimeBaseStructure.TIM_Period = 30;  TIM_TimeBaseStructure.TIM_ClockDivision = 0;  TIM_TimeBaseStructure.TIM_RepetitionCounter = 0;  TIM_TimeBaseInit(TIM1, &TIM_TimeBaseStructure);    /* Channel 1, 2,3 and 4 Configuration in PWM mode */  TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;  TIM_OCInitStructure.TIM_Pulse = 6;  TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low;  TIM_OC1Init(TIM1, &TIM_OCInitStructure);  TIM_ARRPreloadConfig(TIM1, ENABLE);  TIM_OC1PreloadConfig (TIM1, TIM_OCPreload_Enable);  TIM_CtrlPWMOutputs(TIM1, ENABLE);  /* TIM1 counter enable */  TIM_Cmd(TIM1, ENABLE); }