How to make Sim548c - GSM part working with arduino

[tarose78]

Hi,

I tried to make GSM part from sim548c working, So I can play around its AT Command.
I made the schema as follow.
The power source is from LM2596 adjusted at 4.2v with (+) connected to 4 pins VBAT. The status pin is connected to the led, so I know when it is turn-on. It is light-on, means the gsm part should be in active mode.
TX pin is connected to pin-2 of arduino.
Arduino code is very simple (taken from tronixstuff).

/* SparkFun Cellular Shield - Pass-Through Sample Sketch

SparkFun Electronics Written by Ryan Owens CC by v3.0 3/8/10

Thanks to Ryan Owens and Sparkfun for sketch */

#include <NewSoftSerial.h>  //Include the NewSoftSerial library to send serial commands to the cellular module.
#include <string.h>         //Used for string manipulations
char incoming_char=0;      //Will hold the incoming character from the Serial Port.
NewSoftSerial cell(2,3);  //Create a 'fake' serial port. Pin 2 is the Rx pin, pin 3 is the Tx pin.
void setup()
{
  //Initialize serial ports for communication.
  Serial.begin(9600);
  cell.begin(9600);
  Serial.println("Starting SIM548C Communication...");
}
void loop()
{
  //If a character comes in from the cellular module...
  if(cell.available() >0)
  {
    Serial.println("GSM Activated");
    incoming_char=cell.read();    //Get the character from the cellular serial port.
    Serial.print(incoming_char);  //Print the incoming character to the terminal.
  }
  //If a character is coming from the terminal to the Arduino...
  if(Serial.available() >0)
  {
    incoming_char=Serial.read();  //Get the character coming from the terminal
    cell.print(incoming_char);    //Send the character to the cellular module.
  }
}

Response From the terminal :

Starting SIM548C Communication...

Sometimes there is 2 lines of

GSM Activated
GSM Activated

Then no more response for more than 10minutes.

In my opinion, when the gsm part is activated there should be lines with "GSM Activated" over-and-over again.

Please help, Am I missing something here ?