Display CO2 ppm value contains in air.

Driver_CO2.cpp

#include "Arduino.h"
#include "TM74.h"
#define DIO 5
#define RCLK 6
#define SCLK 7

#define ALARM 10

TM74 display(SCLK, RCLK, DIO);

const int analogInPin = A5; 
const int ledPin = 13;
int raw_adc = 0;
float sensorValue = 0;


                     
void setup() {
  pinMode(ledPin, OUTPUT);
  pinMode(ALARM, OUTPUT);
}
  
void loop() {
  raw_adc = analogRead(analogInPin);
  sensorValue = ((10000.0 / 4096.0) * (raw_adc )) + 200;
  if (sensorValue >= 800)
  {
    digitalWrite(ledPin, HIGH);
    digitalWrite(ALARM, 122);
    
  }
  else 
  {
    digitalWrite(ledPin, LOW);
    digitalWrite(ALARM, LOW);
  }
    
  draw(sensorValue);
}

String ValueToString(int value){
  if(value > 9999)
    return "DEAD";
  if(value > 999)
    return String(value);
  if(value > 99)
    return String("0") + String(value);
  if(value > 9)
    return String("00") + String(value);
  return String("000") + String(value);
}

void draw(int CO_value){
  String result = ValueToString(CO_value);
  Segment segs[] = {
    Segment(result[3]),
    Segment(result[2]),
    Segment(result[1]),
    Segment(result[0])
  };
  display.writeSegments(segs, sizeof(segs) / sizeof(Segment));
}

specs:

Arduino Uno
MQ-9, Buzzer, 4-segment display TM74