MH-Z14A CO2 Sensor

#include <MySensor.h>
#include <SPI.h>

#define CHILD_ID 0
#define CO2_SENSOR_PWM_PIN 2

unsigned long SLEEP_TIME = 30*1000; // Sleep time between reads (in milliseconds)

float valAIQ =0.0;
float lastAIQ =0.0;
unsigned long duration;
long ppm;
MySensor gw;
MyMessage msg(CHILD_ID, V_LEVEL);

void setup()
{
  gw.begin();

  // Send the sketch version information to the gateway and Controller
  gw.sendSketchInfo("AIQ Sensor CO2 MH-Z14A", "1.0");

  // Register all sensors to gateway (they will be created as child devices)
  gw.present(CHILD_ID, S_AIR_QUALITY);

  pinMode(CO2_SENSOR_PWM_PIN, INPUT);

}

void loop() {

  while(digitalRead(CO2_SENSOR_PWM_PIN) == HIGH) {;}
  //wait for the pin to go HIGH and measure HIGH time
  duration = pulseIn(CO2_SENSOR_PWM_PIN, HIGH, 2000000);
  ppm = 5000 * ((duration/1000) - 2)/1000;
  Serial.print(ppm);
  if ((ppm != lastAIQ)&&(abs(ppm-lastAIQ)>=10)) {
      gw.send(msg.set((long)ceil(ppm)));
      lastAIQ = ceil(ppm);
  }

  gw.sleep(SLEEP_TIME); //sleep for: sleepTime
}

Credit to alexsh1
https://forum.mysensors.org/topic/3821/mh-z14a-co2-sensor/4