ESP32AnalogRead.cpp

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/*
 * ESP32AnalogRead.cpp
 *
 *  Created on: Apr 10, 2020
 *      Author: hephaestus
 *      https://github.com/madhephaestus/ESPMutexDemo/blob/DSPTest/ESPMutexDemo.ino
 */

#include "ESP32AnalogRead.h"

ESP32AnalogRead::ESP32AnalogRead(int pinNum) {
    if (!(pinNum < 0)) {
        attach(pinNum);
    }
}
void ESP32AnalogRead::attach(int pin) {
    myPin = pin;
    channel = (adc_channel_t) digitalPinToAnalogChannel(myPin);
    attached = true;
}

float ESP32AnalogRead::readVoltage() {
    float mv = readMiliVolts();

    return mv * 0.001;
}
uint32_t ESP32AnalogRead::readMiliVolts() {
    if (!attached)
        return 0;
    analogRead(myPin);
    // Configure ADC

    if (myPin > 27) {
        adc1_config_width(ADC_WIDTH_12Bit);
        adc1_channel_t chan= ADC1_CHANNEL_0;
        switch (myPin) {

        case 36:
            chan = ADC1_CHANNEL_0;
            break;
        case 37:
            chan = ADC1_CHANNEL_1;
            break;
        case 38:
            chan = ADC1_CHANNEL_2;
            break;
        case 39:
            chan = ADC1_CHANNEL_3;
            break;
        case 32:
            chan = ADC1_CHANNEL_4;
            break;
        case 33:
            chan = ADC1_CHANNEL_5;
            break;
        case 34:
            chan = ADC1_CHANNEL_6;
            break;
        case 35:
            chan = ADC1_CHANNEL_7;
            break;
        }
        adc1_config_channel_atten(chan, ADC_ATTEN_11db);
    } else {
        adc2_channel_t chan= ADC2_CHANNEL_0;
        switch (myPin) {
        case 4:
            chan = ADC2_CHANNEL_0;
            break;
        case 0:
            chan = ADC2_CHANNEL_1;
            break;
        case 2:
            chan = ADC2_CHANNEL_2;
            break;
        case 15:
            chan = ADC2_CHANNEL_3;
            break;
        case 13:
            chan = ADC2_CHANNEL_4;
            break;
        case 12:
            chan = ADC2_CHANNEL_5;
            break;
        case 14:
            chan = ADC2_CHANNEL_6;
            break;
        case 27:
            chan = ADC2_CHANNEL_7;
            break;
        case 25:
            chan = ADC2_CHANNEL_8;
            break;
        case 26:
            chan = ADC2_CHANNEL_9;
            break;
        }
        adc2_config_channel_atten(chan, ADC_ATTEN_11db);
    }

    // Calculate ADC characteristics i.e. gain and offset factors
    esp_adc_cal_get_characteristics(V_REF, ADC_ATTEN_DB_11, ADC_WIDTH_BIT_12,
            &characteristics);
    uint32_t voltage = 0;
    // Read ADC and obtain result in mV
    esp_adc_cal_get_voltage(channel, &characteristics, &voltage);
    return voltage - 50;
}