nano_mh-z19_co2.ino

#include <Arduino.h>
#include "MHZ19.h"                        
#include <SoftwareSerial.h>                 //  <--- Remove if using HardwareSerial / ESP32
 
#define RX_PIN 7 
#define TX_PIN 6 
#define BAUDRATE 9600                       // Native to the sensor (do not change)

MHZ19 myMHZ19;
SoftwareSerial mySerial(RX_PIN, TX_PIN);

unsigned long getDataTimer = 0;

void setup()
{
    Serial.begin(115200);  
   
    mySerial.begin(BAUDRATE);              

    myMHZ19.begin(mySerial);                // *Imporant, Pass your Stream reference here

    myMHZ19.autoCalibration(false);         // Turn ABC OFF
}

void loop() {
    if (millis() - getDataTimer >= 2000) {
        int16_t CO2Unlimited = myMHZ19.getCO2(true, true);
        if(myMHZ19.errorCode != RESULT_OK) {
            Serial.println("Error found in communication ");
        } else {
            Serial.print("CO2_PPM_Unlim: ");
            Serial.println(CO2Unlimited);
        }
        getDataTimer = millis(); // Update interval
    }
}