ADC Bug

[pietro2]

Posted on May 20, 2013 at 12:17

Hi guys, i use am stm32f0 microcontroller.

I've a problem about the ADC channel 13 (PC3 pin) and PA3 pin.when i connect something to PA3 pin seems that the ADC PC3 pin reads the PA3 pin value.this is my ADC configuration code:void ADC1_Config(void){  ADC_InitTypeDef          ADC_InitStructure;  GPIO_InitTypeDef         GPIO_InitStructure;  TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;  TIM_OCInitTypeDef        TIM_OCInitStructure;     /* Abilita Periph clock GPIOC  */  RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOC, ENABLE);    /* Abilita ADC1 Periph clock  */  RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC1, ENABLE);    /* Abilita TIM3 Periph clock  */  RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);    /* Configura ADC Channel11 come ingresso analogico */  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_1|GPIO_Pin_3;  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AN;  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_DOWN  ;  GPIO_Init(GPIOC, &GPIO_InitStructure);    /* Configurazione TIM3  *******************************************************/  TIM_DeInit(TIM3);    TIM_TimeBaseStructInit(&TIM_TimeBaseStructure);    TIM_OCStructInit(&TIM_OCInitStructure);      /* Time base configuration */  TIM_TimeBaseStructure.TIM_Period = 0xFF;  TIM_TimeBaseStructure.TIM_Prescaler = 0x0;  TIM_TimeBaseStructure.TIM_ClockDivision = 0x0;  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;    TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);    /* Seleziona TIM3 TRGO  */  TIM_SelectOutputTrigger(TIM3, TIM_TRGOSource_Update);    /* Configurazione ADC1  *******************************************************/  /* Reset ADC  */    ADC_DeInit(ADC1);    /* Configura l' ADC1 in continous mode con una risoluzione di 12 bit*/  ADC_InitStructure.ADC_Resolution = ADC_Resolution_12b;  ADC_InitStructure.ADC_ContinuousConvMode = ENABLE;  ADC_InitStructure.ADC_ExternalTrigConvEdge = ADC_ExternalTrigConvEdge_Rising;      ADC_InitStructure.ADC_ExternalTrigConv = ADC_ExternalTrigConv_T3_TRGO;  ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Right;  ADC_InitStructure.ADC_ScanDirection = ADC_ScanDirection_Upward;  ADC_Init(ADC1, &ADC_InitStructure);     /* Converte l'ADC1 Channel 11 con sampling time pari a 239.5 cicli */   ADC_ChannelConfig(ADC1, ADC_Channel_11 , ADC_SampleTime_28_5Cycles );     ADC_ChannelConfig(ADC1, ADC_Channel_13 , ADC_SampleTime_28_5Cycles);  /* Calibrazione ADC  */  ADC_GetCalibrationFactor(ADC1);      ADC_WaitModeCmd(ADC1, ENABLE);   ADC_AutoPowerOffCmd(ADC1, ENABLE);     /* Abilita l'ADC */  ADC_Cmd(ADC1, ENABLE);         /* Attesa per il flag ADCEN  */  while(!ADC_GetFlagStatus(ADC1, ADC_FLAG_ADEN));     /* Abilita counter TIM2  */  TIM_Cmd(TIM3, ENABLE);    /* Avvia conversione software regolare dell' ADC1 */   ADC_StartOfConversion(ADC1);}every x seconds starts a timer routine that calls the adc reading functionthese reading function is:void LeggiADC(void){    static short value=0;//indica quale variabile deve essere salvata dall'ADC  /* Acquisizione dati convertiti dll'ADC1 */    ADC1ConvertedValue = ADC_GetConversionValue(ADC1);    value++;    /* Calcolo della tensione del sensore di luminosit� */    if (value==1){     mVLux = ((ADC1ConvertedValue * mV_VDDA_ref)/0xFFF);      }else if (value==2){      /* Calcolo della tensione del sensore di temperatura */      mVTemp = ((ADC1ConvertedValue * mV_VDDA_ref)/0xFFF);     value=0;    }    if(( GPIO_ReadInputDataBit(GPIOA, GPIO_Pin_6))==SET){      NewSP=mVDAC;      KTaratura= (float)(LUX)/2;      EE_WriteVariable(0x6011, KTaratura);    }    }if i connect pin PA3 to 3V, the mVTemp value is 3V... why? #adc-problem

[bifrost]

Posted on May 20, 2013 at 14:20 ciao 😉 is your ADC pin left floating? if yes, it is normal to have random reading influenced by external ambient. you should connect the pin with a pull-down or a pull-up. Once you have connected your sensors, these pull-up/pull-down normally can be eliminated, but you should look at your sensor's datasheet.

[anyuping1]

Posted on May 25, 2013 at 19:57

Try something LIKE this way:

short value=0;//indica quale variabile deve essere salvata dall'ADC void LeggiADC(void) {        /* Acquisizione dati convertiti dll'ADC1 */     ADC1ConvertedValue = ADC_GetConversionValue(ADC1);     value++;     /* Calcolo della tensione del sensore di luminosità */     if (value==1){      mVLux = ((ADC1ConvertedValue * mV_VDDA_ref)/0xFFF);        }else if (value==2){       /* Calcolo della tensione del sensore di temperatura */       mVTemp = ((ADC1ConvertedValue * mV_VDDA_ref)/0xFFF);      value=0;     }     if(( GPIO_ReadInputDataBit(GPIOA, GPIO_Pin_6))==SET){       NewSP=mVDAC;       KTaratura= (float)(LUX)/2;       EE_WriteVariable(0x6011, KTaratura);     }      }