[HELP] SD card shield + Arduino + RFID Reader

Using Arduino Programming Questions
#1

I am currently building something, and it works fine as I am testing the device.

Basically the project would scan student RFID cards, then record another set of RFID cards to their accounts(in the SD card).

All is going well, but until I add more “Student Accounts”, the data that was stored before cannot be read anymore, but as i test the card, the data is there, but it just doesn’t seem to be read when the new code is flashed.

Here’s a copy of the code:

#include <SoftwareSerial.h>
#include <SD.h>
SoftwareSerial RFID(2, 3); 

int i;
int c;
int pi;
String pie;
String readID;
String readB;
String cID;
String cB;
String bookS;
String BB;
int R = 6;
int B = 5;
int Re = 7;

void setup()
{
  RFID.begin(9600);
  Serial.begin(9600);
  pinMode(R, INPUT);
  pinMode(B, INPUT);
  pinMode(Re, INPUT);
  while (!Serial) 
  {;}
  
  Serial.print("Initializing SD card..."); 
  pinMode(10, OUTPUT);
   
  if (!SD.begin(4)) {
    Serial.println("initialization failed!");
    return;
  }
  Serial.println("initialization done.");
}

void scan()
{
  if (RFID.available() > 0) 
{
  i = RFID.read();
  c = c + 1;
  pie += i;
}
 
 if (c == 14)
 {
   c = 0;
   pi = 0;
   readID = pie;
   pie = "";
 } 
}
  
void loop()
{
  int Rx = digitalRead(R);
  int Bx = digitalRead(B);
  int Rex = digitalRead(Re);
  
  if ((Rx == 1))
    {
      readS();
      Rx = 0;
    }
  
  if ((Rx == 0))
    {}
  
  if ((Bx == 1))
    {
      borrow();
      Bx = 0;
    }
  
  if ((Bx == 0))
    {}
    
    if ((Rex == 1))
    {
      returnBooks();
      Rex = 0;
    }
    
    if ((Rex == 0))
    {
    }
}


void readS()
{
  scan();
  
if ((readID == "24848484848565555565270663"))
   {
     Serial.println("Oginne Lapuz");
     cID = readID;
     File oginneFile = SD.open("oginne.txt");
      if (oginneFile) {
        while (oginneFile.available()) 
        {
          Serial.write(oginneFile.read());
        }
        
        oginneFile.close();
      } 
      else 
      {
        Serial.println("No Borrowed books");
      }
     readID = "";
     i = 0;   
     bookS = "";
   }
   
   if ((readID == "24848484848566556576851683"))
   {
     Serial.println("Darryl Cacho");
     cID = readID;
     File darrylFile = SD.open("darryl.txt");
      if (darrylFile) {
        while (darrylFile.available()) 
        {
          Serial.write(darrylFile.read());
        }
        
        darrylFile.close();
      } 
      else 
      {
        Serial.println("No Borrowed books");
      }
     readID = "";
     i = 0;   
     bookS = "";
   }
   
      if ((readID == "24865484856575348665354543"))
   {
     Serial.println("Mayee Perdon");
     cID = readID;
     File mayeeFile = SD.open("mayee.txt");
      if (mayeeFile) {
        while (mayeeFile.available()) 
        {
          Serial.write(mayeeFile.read());
        }
        
        mayeeFile.close();
      } 
      else 
      {
        Serial.println("No Borrowed books");
      }
     readID = "";
     i = 0;   
     bookS = "";
   }
   
   if ((readID == "24865484856576966556849533"))
   {
     Serial.println("Fae");
     cID = readID;
     File faeFile = SD.open("fae.txt");
      if (faeFile) {
        while (faeFile.available()) 
        {
          Serial.write(faeFile.read());
        }
        
        faeFile.close();
      } 
      else 
      {
        Serial.println("No Borrowed books");
      }
     readID = "";
     i = 0;   
     bookS = "";
   }
}

void borrow()
{  
  scan();
  
  if ((cID == "24848484848565555565270663") && (i == 3))
   {
     books();
     File oginneFile = SD.open("oginne.txt", FILE_WRITE);
     Serial.println(bookS);
     oginneFile.println(bookS);
     oginneFile.close();
     i = 0;
  }
  
    if ((cID == "24865484856575348665354543") && (i == 3))
   {
     books();
     File mayeeFile = SD.open("mayee.txt", FILE_WRITE);
     Serial.println(bookS);
     mayeeFile.println(bookS);
     mayeeFile.close();
     i = 0;
  }
  
      if ((cID == "24848484848566556576851683") && (i == 3))
   {
     books();
     File darrylFile = SD.open("darryl.txt", FILE_WRITE);
     Serial.println(bookS);
     darrylFile.println(bookS);
     darrylFile.close();
     i = 0;
  }
  
      if ((cID == "24865484856576966556849533") && (i == 3))
   {
     books();
     File faeFile = SD.open("fae.txt", FILE_WRITE);
     Serial.println(bookS);
     faeFile.println(bookS);
     faeFile.close();
     i = 0;
  }
}

void books()
{
  if ((readID == "24857484849556570685654573"))
    {
      bookS = "Book of cheese";
      readID = "";
    }

  if ((readID == "24857484849557066516968663"))
    {
      bookS = "Book of math";
      readID = "";
    }

  if ((readID == "24857484849556570515156503"))
    {
      bookS = "Engineering Electromagnetics";
      readID = "";
    }

   if ((readID == "24857484849564851555754663"))
    {
      bookS = "Engineering Communications";
      readID = "";
    }
}

void returnBooks()
{
  
   if ((cID == "24848484848565555565270663"))
     {
       SD.remove("oginne.txt");
       Serial.println("Books are cleared for Oginne Lapuz");
     }
     
      if ((cID == "24848484848566556576851683"))
     {
       SD.remove("mayee.txt");
       Serial.println("Books are cleared for Mayee Perdon");
     }
     
       if ((cID == "24865484856575348665354543"))
     {
       SD.remove("darryl.txt");
       Serial.println("Books are cleared for Darryl Cacho");
     }
 
}

Thanks for any input!

#2 
String pie;
String readID;
String readB;
String cID;
String cB;
String bookS;
String BB;

There’s your problem right there.

  c = c + 1;

Did you ever wonder why the language that we use to program the Arduino was called C++ rather than C=C+1?

  if ((Rx == 1))

((((((Maybe you need more parentheses)))))))

It’s time for you to do some research, and see just how much memory your Arduino has, and how much of it you are using.
http://playground.arduino.cc/Code/AvailableMemory

#3

Thanks for your reply!

I agree on the string part, and the memory. I solved the problem by converting the strings into integers, and I noticed that it made a huge improvement!

The C++, well, I am still learning the ropes, and it just seemed like the first step into it. Thanks for the tip!

I'll give a look into the parenthesis. The arduino IDE should have an auto-arrange shortcut.

Thanks for the link. I already suspected a memory issue, and I was just asking for comments. I am planning to clean up the code further once the operation is quite solid to my design.

Thanks for your reply once again!

#4