시리얼 모니터를 혼자 공부하는중에 초음파를 이용해 거리측정한 값을 시리얼 모니터와 7-segment에 나타내는것입니다 그중 7-segment와 초음파 모두 정상 작동하지만 시리얼 모니터에만 오류가 생기네요 ㅠㅠ

오류:시리얼 모니터에 거리(cm)가 안나오고 ㅁ 칸만 나옵니다  

아두이노 파일: 

#include<arduino.h>

#define ledA 3
#define ledB 7
#define ledC 11
#define ledD 9
#define ledE 8
#define ledF 4
#define ledG 12
//#define DOT 10
#define seg1 1
#define seg2 5
#define seg3 6
#define seg4 13

/*void charfind(int n)
{
switch(n)
{
  case 1 :
  //A
  digitalWrite(ledD,LOW);
  digitalWrite(ledE,HIGH);
  digitalWrite(ledF,HIGH);
  digitalWrite(ledG,HIGH);
  digitalWrite(ledA,HIGH);
  digitalWrite(ledB,HIGH);
  digitalWrite(ledC,HIGH);
  digitalWrite(DOT, LOW);
  break;

  case 2:
  //B
  digitalWrite(ledD,HIGH);
  digitalWrite(ledE,HIGH);
  digitalWrite(ledF,HIGH);
  digitalWrite(ledG,HIGH);
  digitalWrite(ledA,HIGH);
  digitalWrite(ledB,HIGH);
  digitalWrite(ledC,HIGH);
  digitalWrite(DOT, LOW);
  break;

  case 3:
  //C
  digitalWrite(ledD,HIGH);
  digitalWrite(ledE,HIGH);
  digitalWrite(ledF,HIGH);
  digitalWrite(ledG,LOW);
  digitalWrite(ledA,HIGH);
  digitalWrite(ledB,LOW);
  digitalWrite(ledC,LOW);
  digitalWrite(DOT,LOW);
  break;

  case 4:
  //D
  digitalWrite(ledD,HIGH);
  digitalWrite(ledE,HIGH);
  digitalWrite(ledF,HIGH);
  digitalWrite(ledG,LOW);
  digitalWrite(ledA,HIGH);
  digitalWrite(ledB,HIGH);
  digitalWrite(ledC,HIGH);
  digitalWrite(DOT,LOW);
  break;

  case 5:
  //E
  digitalWrite(ledD,HIGH);
  digitalWrite(ledE,HIGH);
  digitalWrite(ledF,HIGH);
  digitalWrite(ledG,HIGH);
  digitalWrite(ledA,HIGH);
  digitalWrite(ledB,LOW);
  digitalWrite(ledC,LOW);
  digitalWrite(DOT,LOW);
  break;

  case 6:
  digitalWrite(ledD,LOW);
  digitalWrite(ledE,HIGH);
  digitalWrite(ledF,HIGH);
  digitalWrite(ledG,HIGH);
  digitalWrite(ledA,HIGH);
  digitalWrite(ledB,LOW);
  digitalWrite(ledC,LOW);
  digitalWrite(DOT,LOW);
  break;
}
}
*/
void fnd(int n)
{
  switch(n)
  {
    case 0:
   digitalWrite(ledA,HIGH);
   digitalWrite(ledB,HIGH);
   digitalWrite(ledC,HIGH);
   digitalWrite(ledD,HIGH);
   digitalWrite(ledE,HIGH);
   digitalWrite(ledF,HIGH);
   digitalWrite(ledG,LOW);
   //digitalWrite(DOT,LOW);
   break;

   case 1: 
  digitalWrite(ledA,LOW);
  digitalWrite(ledB,HIGH);
  digitalWrite(ledC,HIGH);
  digitalWrite(ledD,LOW);
  digitalWrite(ledE,LOW);
  digitalWrite(ledF,LOW);
  digitalWrite(ledG,LOW);
 // digitalWrite(DOT,LOW);
  break;

   case 2: 
  digitalWrite(ledA,HIGH);
  digitalWrite(ledB,HIGH);
  digitalWrite(ledC,LOW);
  digitalWrite(ledD,HIGH);
  digitalWrite(ledE,HIGH);
  digitalWrite(ledF,LOW);
  digitalWrite(ledG,HIGH);
  //digitalWrite(DOT,LOW);
  break;
  
   case 3: 
  digitalWrite(ledA,HIGH);
  digitalWrite(ledB,HIGH);
  digitalWrite(ledC,HIGH);
  digitalWrite(ledD,HIGH);
  digitalWrite(ledE,LOW);
  digitalWrite(ledF,LOW);
  digitalWrite(ledG,HIGH);
  //digitalWrite(DOT,LOW);
  break;

   case 4: 
  digitalWrite(ledA,LOW);
  digitalWrite(ledB,HIGH);
  digitalWrite(ledC,HIGH);
  digitalWrite(ledD,LOW);
  digitalWrite(ledE,LOW);
  digitalWrite(ledF,HIGH);
  digitalWrite(ledG,HIGH);
  //digitalWrite(DOT,LOW);
  break;

   case 5: 
  digitalWrite(ledA,HIGH);
  digitalWrite(ledB,LOW);
  digitalWrite(ledC,HIGH);
  digitalWrite(ledD,HIGH);
  digitalWrite(ledE,LOW);
  digitalWrite(ledF,HIGH);
  digitalWrite(ledG,HIGH);
 // digitalWrite(DOT,LOW);
  break;

   case 6: 
  digitalWrite(ledA,HIGH);
  digitalWrite(ledB,LOW);
  digitalWrite(ledC,HIGH);
  digitalWrite(ledD,HIGH);
  digitalWrite(ledE,HIGH);
  digitalWrite(ledF,HIGH);
  digitalWrite(ledG,HIGH);
 // digitalWrite(DOT,LOW);
  break;

   case 7: 
  digitalWrite(ledA,HIGH);
  digitalWrite(ledB,HIGH);
  digitalWrite(ledC,HIGH);
  digitalWrite(ledD,LOW);
  digitalWrite(ledE,LOW);
  digitalWrite(ledF,LOW);
  digitalWrite(ledG,LOW);
  //digitalWrite(DOT,LOW);
  break;

   case 8: 
  digitalWrite(ledA,HIGH);
  digitalWrite(ledB,HIGH);
  digitalWrite(ledC,HIGH);
  digitalWrite(ledD,HIGH);
  digitalWrite(ledE,HIGH);
  digitalWrite(ledF,HIGH);
  digitalWrite(ledG,HIGH);
  //digitalWrite(DOT,LOW);
  break;

   case 9: 
  digitalWrite(ledA,HIGH);
  digitalWrite(ledB,HIGH);
  digitalWrite(ledC,HIGH);
  digitalWrite(ledD,HIGH);
  digitalWrite(ledE,LOW);
  digitalWrite(ledF,HIGH);
  digitalWrite(ledG,HIGH);
  //digitalWrite(DOT,LOW);
  break;

  case 10:
   digitalWrite(ledA,HIGH);
   digitalWrite(ledB,HIGH);
   digitalWrite(ledC,HIGH);
   digitalWrite(ledD,HIGH);
   digitalWrite(ledE,HIGH);
   digitalWrite(ledF,HIGH);
   digitalWrite(ledG,LOW);
   //digitalWrite(DOT,LOW);
   break;
  }
}

 void clr(){
    
  digitalWrite(ledA,LOW);
  digitalWrite(ledB,LOW);
  digitalWrite(ledC,LOW);
  digitalWrite(ledD,LOW);
  digitalWrite(ledE,LOW);
  digitalWrite(ledF,LOW);
  digitalWrite(ledG,LOW);
  //digitalWrite(DOT,LOW);
  delay(500);
 }

 void set(){
  digitalWrite(ledA,HIGH);
  digitalWrite(ledB,HIGH);
  digitalWrite(ledC,HIGH);
  digitalWrite(ledD,HIGH);
  digitalWrite(ledE,HIGH);
  digitalWrite(ledF,HIGH);
  digitalWrite(ledG,HIGH);
  //digitalWrite(DOT,HIGH);
  delay(500);
 }

int a[4]={0,0,0,0};

void setup() {
   pinMode(ledA,OUTPUT);
   pinMode(ledB,OUTPUT);
   pinMode(ledC,OUTPUT);
   pinMode(ledD,OUTPUT);
   pinMode(ledE,OUTPUT);
   pinMode(ledF,OUTPUT);
   pinMode(ledG,OUTPUT);
  // pinMode(DOT,OUTPUT);
   pinMode(seg1,OUTPUT);
   pinMode(seg2,OUTPUT);
   pinMode(seg3,OUTPUT);
   pinMode(seg4,OUTPUT);
   pinMode(2,INPUT);
   pinMode(10,OUTPUT);
      Serial.begin(9600);
}
void loop() {

  long duration, cm;
  digitalWrite(10,LOW);
  delayMicroseconds(2);

 digitalWrite(10,HIGH);
 delayMicroseconds(10);

 digitalWrite(10,LOW);

 duration = pulseIn(2,HIGH);

 cm=(duration/2)/29.1;
 
  a[3]=cm;
  a[2]=cm/10;
  a[1]=cm/100;
  a[0]=cm/1000;
    Serial.print(cm);
    Serial.println("cm");
  
  
 

  
  digitalWrite(seg1,LOW);
  fnd(a[0]);
  delay(5);
  digitalWrite(seg1,HIGH);

  
  digitalWrite(seg2,LOW);
  fnd(a[1]);
  delay(5);
  digitalWrite(seg2,HIGH);

  
  digitalWrite(seg3,LOW);
  fnd(a[2]);
  delay(5);
  digitalWrite(seg3,HIGH);

  
  digitalWrite(seg4,LOW);
  fnd(a[3]);
  delay(5);
  digitalWrite(seg4,HIGH);
  
}