STM32F303 ADC Sequence Conversion Problem

[MAbba.8]

Hello I am trying to use STM32F303VCT6 ADC1 to measure 4 channels in sequence. I am using TIMER 3 to trigger start of sequence conversion. I am using DMA1 to transfer data to an array. My code is as follows:

ADC Configuration:

ADC_InitTypeDef       ADC_InitStructure;
ADC_CommonInitTypeDef ADC_CommonInitStructure;
 
/* Configure the ADC clock */
  RCC_ADCCLKConfig(RCC_ADC12PLLCLK_Div16);
  
  /* Enable ADC1 clock */
  RCC_AHBPeriphClockCmd(RCC_AHBPeriph_ADC12, ENABLE);
	
  ADC_CommonInitStructure.ADC_Mode = ADC_Mode_Independent;                                                                    
  ADC_CommonInitStructure.ADC_Clock = ADC_Clock_AsynClkMode;                    
  ADC_CommonInitStructure.ADC_DMAAccessMode = ADC_DMAAccessMode_1 ;             
  ADC_CommonInitStructure.ADC_DMAMode = ADC_DMAMode_Circular;                  
  ADC_CommonInitStructure.ADC_TwoSamplingDelay = 0;          
  ADC_CommonInit(ADC1, &ADC_CommonInitStructure);
  
  ADC_InitStructure.ADC_ContinuousConvMode = ADC_ContinuousConvMode_Disable;
  ADC_InitStructure.ADC_Resolution = ADC_Resolution_12b; 
  ADC_InitStructure.ADC_ExternalTrigConvEvent = ADC_ExternalTrigConvEvent_4;     /*TIMER 
 3 Triggers ADC*/     
  ADC_InitStructure.ADC_ExternalTrigEventEdge = ADC_ExternalTrigEventEdge_RisingEdge;
  ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Right;
  ADC_InitStructure.ADC_OverrunMode = ADC_OverrunMode_Disable;   
  ADC_InitStructure.ADC_AutoInjMode = ADC_AutoInjec_Disable;  
  ADC_InitStructure.ADC_NbrOfRegChannel = 4;
  ADC_Init(ADC1, &ADC_InitStructure);
	
   /* ADC1 regular channel1 configuration */ 
  ADC_RegularChannelConfig(ADC1, ADC_Channel_1, 1, ADC_SampleTime_1Cycles5);
  /* ADC1 regular channel2 configuration */ 
  ADC_RegularChannelConfig(ADC1, ADC_Channel_2, 2, ADC_SampleTime_1Cycles5);
   /* ADC1 regular channel3 configuration */ 
  ADC_RegularChannelConfig(ADC1, ADC_Channel_3, 3, ADC_SampleTime_1Cycles5);
  /* ADC1 regular channel4 configuration */ 
  ADC_RegularChannelConfig(ADC1, ADC_Channel_4, 4, ADC_SampleTime_1Cycles5);
	
  ADC_RegularChannelSequencerLengthConfig (ADC1, 4);
	
  /* Configure ADC Channels 1,2,3,4 as analog input */
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0 | GPIO_Pin_1 | GPIO_Pin_2 | GPIO_Pin_3;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AN;
  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL ;
  GPIO_Init(GPIOA, &GPIO_InitStructure);
	
   /* Calibration procedure */  
  ADC_VoltageRegulatorCmd(ADC1, ENABLE);
  
  /* Insert delay equal to 5 ms */
  Delay(5);
  
  ADC_SelectCalibrationMode(ADC1, ADC_CalibrationMode_Single);
  ADC_StartCalibration(ADC1);
	
   while(ADC_GetCalibrationStatus(ADC1) != RESET );
	
   ADC_DMAConfig(ADC1, ADC_DMAMode_Circular);
  ADC_DMACmd(ADC1, ENABLE);
 
  /* Enable ADC1 */
  ADC_Cmd(ADC1, ENABLE);

DMA1 Configuration:

   DMA_InitTypeDef   DMA_InitStructure;
   RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);
	
    DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
    DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)&adc_values; /*Array to hold ADC 
    values*/
    DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC;
    DMA_InitStructure.DMA_Mode = DMA_Mode_Circular;
    DMA_InitStructure.DMA_Priority = DMA_Priority_High;
    DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_HalfWord;
    DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_HalfWord;
    DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
    DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
    DMA_InitStructure.DMA_BufferSize = 4; // in data unit
    DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)&ADC1->DR;
    DMA_Init(DMA1_Channel1, &DMA_InitStructure);
    DMA_Cmd(DMA1_Channel1, ENABLE);

TIMER 3 Configuration:

  TIM_TimeBaseInitTypeDef    TIM_TimeBaseStructure;
 
	
  /* TIM3 Periph clock enable */
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);
 
  /* Time base configuration */
  TIM_TimeBaseStructInit(&TIM_TimeBaseStructure); 
  TIM_TimeBaseStructure.TIM_Period = 0x2328;          
  TIM_TimeBaseStructure.TIM_Prescaler = 0x0;       
  TIM_TimeBaseStructure.TIM_ClockDivision = 0x0;    
  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;  
  TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);
 
  /* TIM3 TRGO selection */
  TIM_SelectOutputTrigger(TIM3, TIM_TRGOSource_Update);
	
  /* TIM3 enable counter */
  TIM_Cmd(TIM3, ENABLE);

In main I have used following code to start the ADC process:

  DMA_Config();
  ADC_Config();
  TIM_Config();
 
   /* wait for ADRDY */
   while(!ADC_GetFlagStatus(ADC1, ADC_FLAG_RDY));
   /* Start ADC1 Software Conversion */
   ADC_StartConversion(ADC1);

The problem I am facing is that my code can only convert the channel which is highest in the sequence. For example, for the configuration given above, I am able to see correct conversion value only on channel 1 of ADC 1, because its rank is 1 in the sequence. I have tried changing the channels in the sequence to confirm that the channel with highest rank i.e. first channel in sequence gets converted. I have not enabled any interrupts.

Kindly see the code and tell me what I am missing.