RFID (SoftwareSerial) influences/breaks connection with SD (SPI)

Question

I'm creating a RFID logger with Arduino. I connected a RFID scanner, RTC module and a SD card reader. All parts are working fine together but when i started combining different sketches a problem occured.

Reading files and writing to files on the SD card is no problem as long as i don't scan a RFID card. When input is received from the RFID scanner it is no longer possible to read or write to the sd card. The connection seems to be "disconnected" as soon as RFID input is received.

I tried using different pins for the RFID scanner, another sequence of initializing in the setup but it doesn't make a difference.

Is this a limitation of the Arduino or am I doing something wrong?

I'm using a ATS125KRW RFID shield and a Catalex MicroSD card adpater in combination with a Arduino Mega.

// SD
#include <SD.h>
File myFile;
char idArray[100][11];
char nameArray[100][11];

// RTC
#include <Wire.h>
#include "RTClib.h"
RTC_DS1307 rtc;

// RFID
#include <SoftwareSerial.h>
SoftwareSerial rfid = SoftwareSerial(A8 , A9); //(RX,TX)
String cardID; //string to store card id
char c;
char cardArray[11];

int incomingByte = 0;   // for incoming serial data

String rfidInput;
boolean logtosd;

void setup()
{
  Serial.begin(9600);
   initializeRFID();

  initializeSD();
  initializeRTC();

  readfromSD();

}

void loop()
{       
  while(rfid.available()>0)
  {
      c = rfid.read(); 
      rfidInput += c;    
  } 

  if(rfidInput.length() >=12)
  {
        Serial.print("SCanned: ");
        Serial.println(rfidInput);
        //writetoSD(rfidInput);
        writetoSD("kaart");
      rfidInput = "";

  }

    while(Serial.available()>0)
  {
      c = Serial.read(); 
      cardID += c;
  } 

  if(cardID.length() >= 2)
  {
    writetoSD(cardID);

    cardID = "";
  }  

}

void initializeSD()
{
    // GND en VCC aansluiting via pin 48 en 49
  pinMode(48, OUTPUT);           // set pin to output
  digitalWrite(48, LOW);         // GND pin dus LOW
  pinMode(49, OUTPUT);           // set pin to output
  digitalWrite(49, HIGH);         // VCC pin dus HIGH

  pinMode(53, OUTPUT);

 if (!SD.begin(53)) 
 {
    Serial.println("SD   initialization failed");
    return;
  }
  Serial.println("SD   initialized");
}

void readfromSD()
{
  //open the file for reading:
  myFile = SD.open("db.txt");

  if (myFile) 
  {
     char line[25];         //Array to store entire line 
     int linenumber = 0;
     int arrayPlace = 0;

     while (myFile.available()) 
     {
        char ch = myFile.read();
        if(ch != '\n')
        {
          line[arrayPlace] = ch;
          arrayPlace ++;
        }

        else
        {      
          char id[11];
          char name[11];

          //get ID from entire line
          for(int x = 0; x <= 10 ; x++)
          {
            id[x] = line[x];
          }

          //Get NAME from entire line
          for(int x = 11; x <= 19 ; x++)
          {
            if (line[x] != ';')
            {
              name[x-11] = line[x];
            }
            else
            { 
              // NULL TERMINATE THE ARRAY
              name[x-11] = '\0';
              //STOP
              x = 20;
            }
          }

          // save name to nameArray       
          for(int x = 0; x <= 11 ; x++)
          {
            nameArray[linenumber][x] = name[x];
          }

          // NULL TERMINATE THE ARRAY
          id[10] = '\0';

          // save id to idArray
          for(int x = 0; x <= 11 ; x++)
          {
            idArray[linenumber][x] = id[x];
          }

          linenumber +=1;
          arrayPlace = 0;
        } //else  
     } //while

      // close the file:
      myFile.close();
  } 
  else 
  {
    // if the file didn't open, print an error:
    Serial.println("error opening db.txt");
  }
}

void writetoSD(String cardID)
{
  //open file for writing
  myFile = SD.open("test.txt", FILE_WRITE);

  // if the file opened okay, write to it:
  if (myFile) 
  {
    Serial.println("Writing time to test.txt...");

    DateTime now = rtc.now();  
    myFile.print(now.day(), DEC);
    myFile.print('/');
    myFile.print(now.month(), DEC);
    myFile.print('/');
    myFile.print(now.year(), DEC);
    myFile.print(' ');
    myFile.print(now.hour(), DEC);
    myFile.print(':');
    myFile.print(now.minute(), DEC);
    myFile.print(':');
    myFile.print(now.second(), DEC);
    myFile.print('\t');

    Serial.println("Writing string to test.txt...");
    myFile.println(cardID);

    // close the file:
    myFile.flush();
    Serial.println("done.");
  } 
  else 
  {
    // if the file didn't open, print an error:
    Serial.println("error opening test.txt");
  }
}

void initializeRTC()
{
   // GND en VCC aansluiting via pin 18 en 19
  pinMode(18, OUTPUT);           // set pin to output
  digitalWrite(18, LOW);         // GND pin dus LOW
  pinMode(19, OUTPUT);           // set pin to output
  digitalWrite(19, HIGH);         // VCC pin dus HIGH

  #ifdef AVR
  Wire.begin();
  #else
  Wire1.begin(); // Shield I2C pins connect to alt I2C bus on Arduino Due
  #endif
  rtc.begin();

  Serial.print("RTC  Initialized: ");

  DateTime now = rtc.now();

    Serial.print(now.day(), DEC);
    Serial.print('/');
    Serial.print(now.month(), DEC);
    Serial.print('/');
    Serial.print(now.year(), DEC);
    Serial.print(' ');
    Serial.print(now.hour(), DEC);
    Serial.print(':');
    Serial.print(now.minute(), DEC);
    Serial.print(':');
    Serial.print(now.second(), DEC);
    Serial.println();

}

void initializeRFID()
{
    rfid.begin(9600);
    Serial.println("RFID initialized"); 
}

score 0 · Answer 1 · answered Sep 11 '15 at 09:23

I think you are running out of RAM ,i have done a lot of data logging on SD card with Arduino and its a very resources taking job for the minial 2kb ram on the UNO (assuming u using UNO). Try using MemoryFree() library before every place you see there might be problem to see if you are running outta memory?

RFID (SoftwareSerial) influences/breaks connection with SD (SPI)

1 Answers1