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 #include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "driver/gpio.h"
#include "driver/adc.h"
#include "driver/timer.h"
#include "esp_timer.h"

#define DEFAULT_VREF    1060        //Use adc2_vref_to_gpio() to obtain a better estimate
#define NO_OF_SAMPLES   1000        //Multisampling

extern "C" {
    void app_main(void);
}

static unsigned long millis() {
    return esp_timer_get_time() / 1000;
}

float adc_reading_2, adc_reading_3 = 0;
int read_raw_1, read_raw_2, adc_reading_4, adc_reading_1 = 0;

void ADC_config(void)
{   
adc_set_clk_div(2);   // ADC clock is divided from the APB Clock

adc1_config_width(ADC_WIDTH_BIT_12);   // select bit width for adc1
adc1_config_channel_atten(ADC1_CHANNEL_5, ADC_ATTEN_11db); // select channel (GPIO 33) and attenuation
adc1_config_channel_atten(ADC1_CHANNEL_4, ADC_ATTEN_11db); // select channel (GPIO 32) and attenuation
adc2_config_channel_atten(ADC2_CHANNEL_6, ADC_ATTEN_11db);  // GPIO 14  
adc2_config_channel_atten(ADC2_CHANNEL_3, ADC_ATTEN_11db);  // GPIO 15         
}

void adc_task (void *pvParameter) 
{ 
     while (1) {
         
        unsigned long t1 = millis(); 
        
        for (uint32_t i = 0; i < NO_OF_SAMPLES; i++) {   
                //adc_reading_1 = adc1_get_raw(ADC1_CHANNEL_6);    
                //adc_reading_2 = adc1_get_raw(ADC1_CHANNEL_5);
                adc_reading_3 = adc1_get_raw(ADC1_CHANNEL_4);
                //adc_reading_1 = adc2_get_raw(ADC2_CHANNEL_3, ADC_WIDTH_BIT_12, &read_raw_1);
                //adc_reading_4 = adc2_get_raw(ADC2_CHANNEL_6, ADC_WIDTH_BIT_12, &read_raw_2);
                //adc_reading_4 = adc2_get_raw(ADC2_CHANNEL_3, ADC_WIDTH_BIT_12, &read_raw_2);
        }
        unsigned long t2 = millis(); 
        unsigned long diff_ms = (t2-t1);  
        printf("Conversion time: %lums\n", diff_ms);  
        printf("Mean time for each ADC reading in us: %0.4f\n", static_cast<double>(diff_ms)/NO_OF_SAMPLES*1000); 
        printf("ADC speed in kSPS: %0.4f\n",static_cast<double>(NO_OF_SAMPLES/diff_ms));
        vTaskDelay(pdMS_TO_TICKS(500)); 
    }
}

void app_main(void)
{
esp_timer_init();
ADC_config();  
xTaskCreatePinnedToCore(adc_task, "adc_task", 2048, NULL, 5, NULL, tskNO_AFFINITY);  
}