ADC Bug

pietro2 · ‎2013-05-20

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 function

these 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 · ‎2013-05-20

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 · ‎2013-05-25

Posted on May 25, 2013 at 19:57

Try something LIKE this way:

short value=0;//indica quale variabile deve essere salvata dall'ADC