I recommend using the ESP32's A:D API over using the Arduino ESP32 core functions.
Here is some code that you might use as a model.
#include <driver/adc.h>
void setup()
{
adc1_config_width(ADC_WIDTH_12Bit);
adc1_config_channel_atten(ADC1_CHANNEL_6, ADC_ATTEN_DB_11);// using GPIO 34 wind direction
adc1_config_channel_atten(ADC1_CHANNEL_3, ADC_ATTEN_DB_11);// using GPIO 39 current
adc1_config_channel_atten(ADC1_CHANNEL_0, ADC_ATTEN_DB_11);// using GPIO 36 battery volts
}
void fReadBattery( void * parameter )
{
//float ADbits = 4096.0f;
//float ref_voltage = 3.3f;
float ADscale = 3.3f / 4096.0f;
float adcValue = 0.0f;
float offSET = 0.0f;
const float r1 = 50500.0f; // R1 in ohm, 50K
const float r2 = 10000.0f; // R2 in ohm, 10k potentiometer
//float Vscale = (r1+r2)/r2;
float Vbatt = 0.0f;
int printCount = 0;
float vRefScale = (3.3f / 4096.0f) * ((r1 + r2) / r2);
uint64_t TimePastKalman = esp_timer_get_time(); // used by the Kalman filter UpdateProcessNoise, time since last kalman calculation
SimpleKalmanFilter KF_ADC_b( 1.0f, 1.0f, .01f );
TickType_t xLastWakeTime = xTaskGetTickCount();
const TickType_t xFrequency = 1000; //delay for mS
for (;;)
{
adc1_get_raw(ADC1_CHANNEL_0); //read and discard
adcValue = float( adc1_get_raw(ADC1_CHANNEL_0) ); //take a raw ADC reading
KF_ADC_b.setProcessNoise( (esp_timer_get_time() - TimePastKalman) / 1000000.0f ); //get time, in microsecods, since last readings
adcValue = KF_ADC_b.updateEstimate( adcValue ); // apply simple Kalman filter
Vbatt = adcValue * vRefScale;
xSemaphoreTake( sema_CalculatedVoltage, portMAX_DELAY );
CalculatedVoltage = Vbatt;
xSemaphoreGive( sema_CalculatedVoltage );
/*
printCount++;
if ( printCount == 3 )
{
log_i( "Vbatt %f", Vbatt );
printCount = 0;
}
*/
TimePastKalman = esp_timer_get_time(); // time of update complete
xLastWakeTime = xTaskGetTickCount();
vTaskDelayUntil( &xLastWakeTime, xFrequency );
//log_i( "fReadBattery %d", uxTaskGetStackHighWaterMark( NULL ) );
}
vTaskDelete( NULL );
}