#include <SPI.h>
#include <SD.h>

File myFile;

int count,Cstep,Tstep;
String sdarr="";
char indata;

void setup() {
  
  pinMode(9,INPUT_PULLUP);
  pinMode(8,INPUT_PULLUP);
  Serial.begin(9600);
  Serial.print("Initializing SD card...");
  
  if (!SD.begin(4)) { // SD카드 모듈을 초기화합니다.
    Serial.println("initialization failed!");
    while (1);
  }
  Serial.println("initialization done.");

  myFile = SD.open("test.txt", FILE_WRITE); // 샘플데이타 생성
  if (myFile) { 
    Serial.print("Writing to test.txt...");
    for(int i=0;i<10;i++){
      myFile.print(" No:");
      myFile.print(count);
      myFile.println(" SD data Read Write test");
      count++;
    }
    myFile.close();
    Serial.println("done.");
    Serial.println("Reading test....Ready!!");
  } else {
      Serial.println("error opening test.txt");
  }

  /*
  count=0;
  myFile = SD.open("test.txt");
  if (myFile) {
    Serial.println("Reading test:");
    while (myFile.available()) {
      char indata = myFile.read();
      if(indata !='\n'){
        sdarr=sdarr+indata;
      }else{
        sdarr=sdarr+'\n';
        Serial.print(count);
        Serial.print(sdarr);
        sdarr="";
        count++;
      }
    }
    myFile.close();
  } else {
    Serial.println("error opening test.txt");
  }
  Serial.println(count);
  */
}

void loop() {

  if(digitalRead(9)==LOW) {  //데이타를 역으로조회
    Tstep = Cstep - 1;
    if(Tstep <= 0)Tstep=count;
  }
  if(digitalRead(8)==LOW) {  //데이타를 정으로 조회
    Tstep = Cstep + 1;
    if(Tstep > count)Tstep=1;
  }
   
  if(Tstep != Cstep){
    myFile = SD.open("test.txt");
    Cstep=0;
    while(Tstep!=Cstep){  
      while (indata !='\n') {
        indata = myFile.read();
        sdarr=sdarr+indata;
      }
      Cstep++;
      if(Tstep==Cstep){
        Serial.print(sdarr);
        myFile.close();
        delay(500);        
      }
      indata=' ';
      sdarr="";
    }
  }
}