Problem with NFC on Arduino MEGA

Question

My Objective :

I am trying to send my Mifare's unique number with some other parameters to my server database. As soon as the tag come closer to NFC, it detects, and some additional details are passed to the server Database.

Steps done :

1. I have Arduino UNO, Arduino GSM shield and Adafruit NFC shield . I had tried my test with UNO and works well. But to add some more features, due to memory salvation it could not be achieved through UNO. Then we moved to MEGA.

2. There are some changes need to be done with MEGA to make [url]http://arduino.cc/en/Guide/GSMShieldLeonardoMega[/url] GSM shield coordinate with the microcontroller[Take the Pin 2 out from GSM shield and with jumper connect Pin 2 with Pin 10]. Then we did and we tested it with GSM web client example and worked fine.

3. Now to accomplish our goal, when we placed NFC shield above the GSM shield and executed same GSM web client example, it is not working. And Suddenly once in a blue moon it connects to the GSM network and works . But often, it fails.

[code]

/*
  Web client

 This sketch connects to a website through a GSM shield. Specifically,
 this example downloads the URL "http://arduino.cc/asciilogo.txt" and 
 prints it to the Serial monitor.

 Circuit:
 * GSM shield attached to an Arduino
 * SIM card with a data plan

 created 8 Mar 2012
 by Tom Igoe

 http://arduino.cc/en/Tutorial/GSMExamplesWebClient

 */

// libraries
#include <GSM.h>

// PIN Number
#define PINNUMBER ""

// APN data
#define GPRS_APN       "GPRS_APN" // replace your GPRS APN
#define GPRS_LOGIN     "login"    // replace with your GPRS login
#define GPRS_PASSWORD  "password" // replace with your GPRS password

// initialize the library instance
GSMClient client;
GPRS gprs;
GSM gsmAccess; 

// URL, path & port (for example: arduino.cc)
char server[] = "arduino.cc";
char path[] = "/asciilogo.txt";
int port = 80; // port 80 is the default for HTTP

void setup()
{
  // initialize serial communications and wait for port to open:
  Serial.begin(115200);
  while (!Serial) {
    ; // wait for serial port to connect. Needed for Leonardo only
  }

  Serial.println("Starting Arduino web client.");
  // connection state
  boolean notConnected = true;

  // After starting the modem with GSM.begin()
  // attach the shield to the GPRS network with the APN, login and password
  while(notConnected)
  {
    if((gsmAccess.begin(PINNUMBER)==GSM_READY) &
      (gprs.attachGPRS(GPRS_APN, GPRS_LOGIN, GPRS_PASSWORD)==GPRS_READY))
      notConnected = false;
    else
    {
      Serial.println("Not connected");
      delay(1000);
    }
  }

  Serial.println("connecting...");

  // if you get a connection, report back via serial:
  if (client.connect(server, port))
  {
    Serial.println("connected");
    // Make a HTTP request:
    client.print("GET ");
    client.print(path);
    client.println(" HTTP/1.1");
    client.print("Host: ");
    client.println(server);
    client.println("Connection: close");
    client.println();
  } 
  else
  {
    // if you didn't get a connection to the server:
    Serial.println("connection failed");
  }
}

void loop()
{
  // if there are incoming bytes available 
  // from the server, read them and print them:
  if (client.available())
  {
    char c = client.read();
    Serial.print(c);
  }

  // if the server's disconnected, stop the client:
  if (!client.available() && !client.connected())
  {
    Serial.println();
    Serial.println("disconnecting.");
    client.stop();

    // do nothing forevermore:
    for(;;)
      ;
  }
}

What is the problem? and where is the problem ?

Answer 1

It is likely that placing the GSM shield between the Arduino Mega and the NFC shield is interfering with the GSM antenna. Antennas react in strange and usually less useful ways when large conductors are placed nearby.

You could try reversing the order of attaching the shields, or you could try spacing the shields further apart using "stackable Arduino headers" (you can do a web search for suppliers). If there is an option for an external antenna, that would be even better.

If you get GSM working, you might still have some trouble with the NFC shield, as it's possible that the GSM transmitter being so close could interfere with the NFD's circuitry - not because they use the same frequences, but just because any conductor so close might pick up electrical noise, and there will be various sensitive circuitry in the NFC electronics.

Answer 2

if your design allows , the NFC is available on a module rather than a shield allowing you to separate the GSM and NFC. like this on ebay