Posted on June 13, 2013 at 09:18Hi,
I've configured ADC1 to sample one of the channels like PA1 (Channel 2). However,
when I connect a power supply to the input, there is a large offset. For example, connecting 2V I can see around 200-250mV offset. Below is my code. I can see the adc value change with the change in input voltage, but I am not sure whether some specific calibration is required. Any insight is appreciated.
GPIO_TypeDef * adcChanPortType;
ADC_InitTypeDef ADC_InitStructure;
ADC_CommonInitTypeDef ADC_CommonInitStructure;
/* Configure the ADC clock */
RCC_ADCCLKConfig(RCC_ADC12PLLCLK_Div2);
/* Enable ADC1/2 clock */
RCC_AHBPeriphClockCmd(RCC_AHBPeriph_ADC12, ENABLE);
/* ADC Channel configuration */
RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOA, ENABLE);
GPIO_InitTypeDef GPIO_InitStructure;
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_1;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AN;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
GPIO_Init(adcChanPortType, &GPIO_InitStructure);
ADC_StructInit(&ADC_InitStructure);
/* Calibration procedure */
ADC_VoltageRegulatorCmd(ADC1, ENABLE);
// Insert delay equal to 10 µs
// To allow regulator to settle
unsigned long int i = 4800;
for(;i>0;i--);
ADC_SelectCalibrationMode(ADC1, ADC_CalibrationMode_Single);
ADC_StartCalibration(ADC1);
while(ADC_GetCalibrationStatus(ADC1) != RESET );
//calibration_value = ADC_GetCalibrationValue(ADC1);
ADC_CommonInitStructure.ADC_Mode = ADC_Mode_Independent;
ADC_CommonInitStructure.ADC_Clock = ADC_Clock_AsynClkMode;
ADC_CommonInitStructure.ADC_DMAAccessMode = ADC_DMAAccessMode_Disabled;
ADC_CommonInitStructure.ADC_DMAMode = ADC_DMAMode_OneShot;
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_0;
ADC_InitStructure.ADC_ExternalTrigEventEdge = ADC_ExternalTrigEventEdge_None;
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 = 1;
ADC_Init(ADC1, &ADC_InitStructure);
/* ADC1 configuration */
ADC_RegularChannelConfig(ADC1, adcChanNum, 1, ADC_SampleTime_181Cycles5);
