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ADC configuration to get 1 value

Question asked by stone.jorge on Oct 1, 2015
Latest reply on Oct 1, 2015 by stone.jorge
Hi, I think this would be very easy but I can't get just 1 value from ADC on stm32f4-disco. I configure ADC like this:

void ADC_Configuration(void)
{
  ADC_CommonInitTypeDef ADC_CommonInitStructure;
  ADC_InitTypeDef ADC_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);
 
  ADC_InitStructure.ADC_Resolution = ADC_Resolution_12b;
  ADC_InitStructure.ADC_ScanConvMode = DISABLE; // 1 Channel
  ADC_InitStructure.ADC_ContinuousConvMode = DISABLE;
  ADC_InitStructure.ADC_ExternalTrigConv = DISABLE;
  ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Right;
  ADC_InitStructure.ADC_NbrOfConversion = 1;
 
  ADC_Init(ADC2, &ADC_InitStructure);
 
  ADC_Cmd(ADC2, ENABLE);
 
  /* ADC2 regular channel 12 configuration */
  ADC_RegularChannelConfig(ADC2, ADC_Channel_12, 2, ADC_SampleTime_15Cycles); // PC2
 
}

And I do in main:

int main(void){
 
      RCC_Configuration();
 
      GPIO_Configuration();
 
      ADC_Configuration();
 
      ADC_SoftwareStartConv(ADC2); //Start ADC2 software conversion
      while(ADC_GetFlagStatus(ADC2, ADC_FLAG_EOC) == RESET); //Wait for conversion complete
      AD_value = ADC_GetConversionValue(ADC2); //Read ADC value
      ADC_ClearFlag(ADC2, ADC_FLAG_EOC); //Clear EOC flag
 
      while(1){
      }
}

The problem is that I get random values. For instance if I connect PC2 (pin associate with ADC2CH12) to 3V I get 200 instead of 4095.

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