Posted on June 09, 2015 at 17:56
I have the ADC reading the voltage drop across a 10k thermistor setup in a voltage divider w/ a 57k resistor. If I probe the board itself I can easily read the voltage drop across the thermistor and to the appropriate input pin of the STM This reading isconsistently 8-10% higher than the 12 bit reading the ADC outputs (so the ADC is reading low). I am using the HAL ADC drivers and the ADC is reading in single conversion mode. I tried adjusting the sampling time to be longer, but it had no impact. Any idea what it could be? I inserted the code I am using for the ADC below (these functions are called by the main program):
#include ''stm32f0xx_hal.h''
#include ''adc.h''
ADC_HandleTypeDef hadc;
/* ADC init function */
void
adc_init(
void
)
{
ADC_ChannelConfTypeDef sConfig;
/**Configure the global features of the ADC (Clock, Resolution, Data Alignment and number of conversion)
*/
hadc.Instance = ADC1;
hadc.Init.ClockPrescaler = ADC_CLOCK_ASYNC;
hadc.Init.Resolution = ADC_RESOLUTION12b;
hadc.Init.DataAlign = ADC_DATAALIGN_RIGHT;
hadc.Init.ScanConvMode = ADC_SCAN_DIRECTION_FORWARD;
hadc.Init.EOCSelection = EOC_SINGLE_CONV;
hadc.Init.LowPowerAutoWait = DISABLE;
hadc.Init.LowPowerAutoPowerOff = DISABLE;
hadc.Init.ContinuousConvMode = DISABLE;
hadc.Init.DiscontinuousConvMode = DISABLE;
hadc.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_NONE;
hadc.Init.DMAContinuousRequests = DISABLE;
hadc.Init.Overrun = OVR_DATA_PRESERVED;
HAL_ADC_Init(&hadc);
/**Configure for the selected ADC regular channel to be converted.
*/
sConfig.Channel = ADC_CHANNEL_0;
sConfig.Rank = 1;
sConfig.SamplingTime = ADC_SAMPLETIME_13CYCLES_5;
HAL_ADC_ConfigChannel(&hadc, &sConfig);
sConfig.Channel = ADC_CHANNEL_2;
sConfig.Rank = 1;
sConfig.SamplingTime = ADC_SAMPLETIME_13CYCLES_5;
HAL_ADC_ConfigChannel(&hadc, &sConfig);
}
uint32_t adc_read(uint32_t channel) {
HAL_StatusTypeDef adc_status;
//ADC_ChannelConfTypeDef sConfig;
//sConfig.Channel = channel;
//HAL_ADC_ConfigChannel(&hadc, &sConfig);
hadc.Instance->CHSELR = 1 << channel;
HAL_ADC_Start(&hadc);
adc_status = HAL_ADC_PollForConversion(&hadc, 1000);
if
(adc_status == HAL_OK) {
return
HAL_ADC_GetValue(&hadc);
}
return
0;
}
#adc #hal #stm32f0
