@Ed1500 I am connecting the Arduino via USB port

@Ed1500 Thank you for your response I will try it. Are you using PWM or not?

Hi,
I am using this code to get C02 value. But always I get this result (CRC 0/0) even after waiting more than 3 min for the healing process.

#include <SoftwareSerial.h>;

SoftwareSerial mySerial(A0, A1); // A0 - к TX сенсора, A1 - к RX

byte cmd[9] = {0xFF,0x01,0x86,0x00,0x00,0x00,0x00,0x00,0x79}; 
unsigned char response[9];

void setup() {
  Serial.begin(9600);
  mySerial.begin(9600);
}

void loop() 
{
  mySerial.write(cmd, 9);
  memset(response, 0, 9);
  mySerial.readBytes(response, 9);
  int i;
  byte crc = 0;
  for (i = 1; i < 8; i++) crc+=response[i];
  crc = 255 - crc;
  crc++;

  if ( !(response[0] == 0xFF && response[1] == 0x86 && response[8] == crc) ) {
    Serial.println("CRC error: " + String(crc) + " / "+ String(response[8]));
  } else {
    unsigned int responseHigh = (unsigned int) response[2];
    unsigned int responseLow = (unsigned int) response[3];
    unsigned int ppm = (256*responseHigh) + responseLow;
    Serial.println(ppm);
  }
  delay(10000);
}

I used the sensor directly without any calibration. Another note, why I can only use 3.3V, the 5v make my Arduino card shutdown