아두이노 이산화탄소 CO2 센서 / CM1106(Single)

#include <SoftwareSerial.h>
 
SoftwareSerial mySerial(13, 11);
unsigned char Send_data[4] = {0x11,0x01,0x01,0xED};
unsigned char Receive_Buff[8];
unsigned char recv_cnt = 0;
unsigned int PPM_Value;
 
void Send_CMD(void) {
  unsigned int i;
  for(i=0; i<4; i++) {
    mySerial.write(Send_data[i]);
    delay(1);
  }
}
unsigned char Checksum_cal(void) {
  unsigned char count, SUM=0;
  for(count=0; count<7; count++) {
     SUM += Receive_Buff[count];
  }
  return 256-SUM;
}
 
void setup() {
  pinMode(13,INPUT);
  pinMode(11,OUTPUT);
  Serial.begin(9600);
  while (!Serial) ;
  mySerial.begin(9600);
  while (!mySerial);
}
 
void loop() {
  Serial.print("Sending...");
  Send_CMD();
  while(1) {
    if(mySerial.available()) { 
       Receive_Buff[recv_cnt++] = mySerial.read();
      if(recv_cnt ==8){recv_cnt = 0; break;}
    }
  } 
  
  if(Checksum_cal() == Receive_Buff[7]) {
     PPM_Value = Receive_Buff[3]<<8 | Receive_Buff[4];
     Serial.write("   PPM : ");
     Serial.println(PPM_Value);
  }
   else {
    Serial.write("CHECKSUM Error");
  }
  delay(1000);
}