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ADC configuration with PC0 and PA0

Question asked by Kelsey Josund on Jun 23, 2017
Latest reply on Jun 23, 2017 by AvaTar

I recognize that this is probably a dumb question but I'm really struggling with it. I've successfully configured ADCs for reads when using PA0 and PA1:

 

void ADC_Setup() {
GPIO_InitTypeDef GPIO_InitStructure;
ADC_InitTypeDef ADC_InitStructure;
ADC_CommonInitTypeDef ADC_CommonInitStructure;
// enable clocks for GPIO and ADC
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);
RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC1, ENABLE);
// configure PA0, PA1 as alternate function inputs
GPIO_StructInit(&GPIO_InitStructure);
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_2MHz;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AIN;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0 | GPIO_Pin_1;
GPIO_Init(GPIOA, &GPIO_InitStructure);
// ADC1 configuration
ADC_CommonStructInit(&ADC_CommonInitStructure);
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_StructInit(&ADC_InitStructure);
ADC_InitStructure.ADC_Resolution = ADC_Resolution_12b;
ADC_InitStructure.ADC_ScanConvMode = DISABLE;
ADC_InitStructure.ADC_ContinuousConvMode = DISABLE;
ADC_InitStructure.ADC_ExternalTrigConvEdge = ADC_ExternalTrigConvEdge_None;
ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Right;
ADC_InitStructure.ADC_NbrOfConversion = 1;
ADC_Init(ADC1, &ADC_InitStructure);
ADC_Cmd(ADC1, ENABLE);
}
uint16_t ADC_GetChannel(uint8_t channel) {
ADC_RegularChannelConfig(ADC1, channel, 1, ADC_SampleTime_84Cycles);
// Start the conversion
ADC_SoftwareStartConv(ADC1);
// Wait until conversion completion
while(ADC_GetFlagStatus(ADC1, ADC_FLAG_EOC) == RESET);
// Get the conversion value
return ADC_GetConversionValue(ADC1);
}
#define CUTOFF_FREQUENCY 10 // Hz
// low-pass filter works using precomputed alpha = 0.5
uint16_t filterVoltageFast(uint16_t oldVal, uint16_t newSample) {
return oldVal + ((newSample - oldVal) >> 1);
}
void ADC_Poll(volatile ADC_Value *adc) {
adc->brake[1] = ADC_GetChannel(0);
adc->throttle[1] = ADC_GetChannel(1);
adc->brake[1] = filterVoltageFast(adc->brake[1], ADC_GetChannel(0));
adc->brake[0] = adc->brake[1];
adc->throttle[1] = filterVoltageFast(adc->throttle[1], ADC_GetChannel(1));
adc->throttle[0] = adc->throttle[1];
}

Which works. Now I'm trying to convert this to work with PA0 and PC0 for the same functionality, just with different pins, and I can't figure out where I'm going wrong. With PA0 and PA1 code does a bit of additional checks with the low pass filter but I've stripped this down to as little as I think it should be able to get by with, and no dice. Currently it reads kind of random values no matter what voltage I apply to the pin.

 

void dev_adc_setup() {
    GPIO_InitTypeDef            GPIO_InitStructure_Throttle;
    GPIO_InitTypeDef            GPIO_InitStructure_Brake;
    ADC_InitTypeDef             ADC_InitStructure;
    ADC_CommonInitTypeDef       ADC_CommonInitStructure;

    

    RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC3, ENABLE);
    ADC_DeInit();

    

    // THROTTLE GPIO SETUP //
    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);


    GPIO_StructInit(&GPIO_InitStructure_Throttle);
    GPIO_InitStructure_Throttle.GPIO_Speed = GPIO_Speed_2MHz;
    GPIO_InitStructure_Throttle.GPIO_Mode = GPIO_Mode_AIN;
    GPIO_InitStructure_Throttle.GPIO_PuPd = GPIO_PuPd_NOPULL;
    GPIO_InitStructure_Throttle.GPIO_Pin = GPIO_Pin_0;
    GPIO_Init(GPIOA, &GPIO_InitStructure_Throttle);

    // BRAKE GPIO SETUP //
    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOC, ENABLE);
 
    GPIO_StructInit(&GPIO_InitStructure_Brake);
    GPIO_InitStructure_Brake.GPIO_Speed = GPIO_Speed_2MHz;
    GPIO_InitStructure_Brake.GPIO_Mode = GPIO_Mode_AIN;
    GPIO_InitStructure_Brake.GPIO_PuPd = GPIO_PuPd_NOPULL;
    GPIO_InitStructure_Brake.GPIO_Pin = GPIO_Pin_0;
    GPIO_Init(GPIOC, &GPIO_InitStructure_Throttle);

    // ADC1 configuration
    ADC_CommonStructInit(&ADC_CommonInitStructure);
    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_StructInit(&ADC_InitStructure);
    ADC_InitStructure.ADC_Resolution = ADC_Resolution_12b;
    ADC_InitStructure.ADC_ScanConvMode = DISABLE;

    ADC_InitStructure.ADC_ContinuousConvMode = DISABLE;
    ADC_InitStructure.ADC_ExternalTrigConvEdge = ADC_ExternalTrigConvEdge_None;
    ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Right;
    ADC_InitStructure.ADC_NbrOfConversion = 1;
    ADC_Init(ADC3, &ADC_InitStructure);

    ADC_Cmd(ADC3, ENABLE);
}


uint16_t dev_readADC(uint8_t channel)
{

 ADC_RegularChannelConfig(ADC1, channel, 1, ADC_SampleTime_84Cycles);
  // start the conversion
  ADC_SoftwareStartConv(ADC1);
  // wait until conversion completion
  while(ADC_GetFlagStatus(ADC1, ADC_FLAG_EOC) == RESET);
  // get the conversion value
  return ADC_GetConversionValue(ADC1);
  }


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