Arduino Cellular Shield Tutorial

The Arduino Cellular Shield allows you to make cellular telephone calls, and send text messages. The brains of this shield is the SM5100B which is a robust cellular module capable of performing many of the tasks of most standard cell phones. This shield requires use of a SIM card to connect to a cellular network. The tutorial that follows is a bare bones tutorial for initializing the shield, and both sending and receiving text messages, and telephone calls. To learn more about the module's functionality, be sure to check out the datasheets on Sparkfun's product page.

You will need:

(x1) Cellular shield
(x1) Stackable Arduino headers
(x1) Quad band antenna
(x1) Arduino Uno

(Note that some of the links on this page are affiliate links. This does not change the cost of the item for you. I reinvest whatever proceeds I receive into making new projects. If you would like any suggestions for alternative suppliers, please let me know.)

Insert the headers into the shield and solder them into place.

/*
SparkFun Cellular Shield - Pass-Through Sample Sketch
SparkFun Electronics
Written by Ryan Owens
3/8/10

Description: This sketch is written to interface an Arduino Duemillanove to a  Cellular Shield from SparkFun Electronics.
The cellular shield can be purchased here: http://www.sparkfun.com/commerce/product_info.php?products_id=9607
In this sketch serial commands are passed from a terminal program to the SM5100B cellular module; and responses from the cellular
module are posted in the terminal. More information is found in the sketch comments.

An activated SIM card must be inserted into the SIM card holder on the board in order to use the device!

This sketch utilizes the NewSoftSerial library written by Mikal Hart of Arduiniana. The library can be downloaded at this URL:
http://arduiniana.org/libraries/NewSoftSerial/

This code is provided under the Creative Commons Attribution License. More information can be found here:
http://creativecommons.org/licenses/by/3.0/

(Use our code freely! Please just remember to give us credit where it's due. Thanks!)
*/

#include <SoftwareSerial.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.

SoftwareSerial 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);
  
  //Let's get started!
  Serial.println("Starting SM5100B Communication...");
}

void loop() {
  //If a character comes in from the cellular module...
  if(cell.available() >0)
  {
    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
if(incoming_char == '~') // If it’s a tilde…

incoming_char = 0x0D;      // ...convert to a carriage return  

else if( incoming_char == '^') // If it’s an up caret…

incoming_char =  0x1A;    // ...convert to ctrl-Z  

cell.print( incoming_char ); // Send the character to the cellular module.
Serial.print( incoming_char ); // Echo it back to the terminal
}

}

/* SM5100B Quck Reference for AT Command Set
*Unless otherwise noted AT commands are ended by pressing the 'enter' key.

1.) Make sure the proper GSM band has been selected for your country. For the US the band must be set to 7.
To set the band, use this command: AT+SBAND=7

2.) After powering on the Arduino with the shield installed, verify that the module reads and recognizes the SIM card.
With a terimal window open and set to Arduino port and 9600 buad, power on the Arduino. The startup sequence should look something
like this:

Starting SM5100B Communication...
    
+SIND: 1
+SIND: 10,"SM",1,"FD",1,"LD",1,"MC",1,"RC",1,"ME",1

Communication with the module starts after the first line is displayed. The second line of communication, +SIND: 10, tells us if the module
can see a SIM card. If the SIM card is detected every other field is a 1; if the SIM card is not detected every other field is a 0.

3.) Wait for a network connection before you start sending commands. After the +SIND: 10 response the module will automatically start trying
to connect to a network. Wait until you receive the following repsones:

+SIND: 11
+SIND: 3
+SIND: 4

The +SIND response from the cellular module tells the the modules status. Here's a quick run-down of the response meanings:
0 SIM card removed
1 SIM card inserted
2 Ring melody
3 AT module is partially ready
4 AT module is totally ready
5 ID of released calls
6 Released call whose ID=<idx>
7 The network service is available for an emergency call
8 The network is lost
9 Audio ON
10 Show the status of each phonebook after init phrase
11 Registered to network

After registering on the network you can begin interaction. Here are a few simple and useful commands to get started:

To make a call:
AT command - ATDxxxyyyzzzz
Phone number with the format: (xxx)yyy-zzz

try ---- cell.print("ATDxxxyyyzzzz");

If you make a phone call make sure to reference the devices datasheet to hook up a microphone and speaker to the shield.

To send a txt message:
AT command - AT+CMGF=1
This command sets the text message mode to 'text.'
AT command = AT+CMGS="xxxyyyzzzz"(carriage return)'Text to send'(CTRL+Z)
This command is slightly confusing to describe. The phone number, in the format (xxx)yyy-zzzz goes inside double quotations. Press 'enter' after closing the quotations.
Next enter the text to be send. End the AT command by sending CTRL+Z. This character can't be sent from Arduino's terminal. Use an alternate terminal program like Hyperterminal,
Tera Term, Bray Terminal or X-CTU.

The SM5100B module can do much more than this! Check out the datasheets on the product page to learn more about the module.*/

Download and install SerialGSM into your Arduino library.

To send a text message visit the Tronixstuff cellular module tutorial and use example code 26.3:
http://tronixstuff.wordpress.com/2011/01/19/tutorial-arduino-and-gsm-cellular-part-one/

If you would like to run the example code to receive a text, connect an LED to pin 8 and put it in series with a 220 ohm resistor to ground.

To send a text message visit the Tronixstuff cellular module tutorial and use example code 26.5:
http://tronixstuff.wordpress.com/2011/01/19/tutorial-arduino-and-gsm-cellular-part-one/

Text one of the following commands to your cellular module:

//turns the LED on
#a1

//turns the LED off
#a0

Connect a microphone and speaker to the shield using grounded audio cable. The center signal wire should go to the audio plus terminals and the shielding should go to the respective negative terminals on the shield. These cables should be connected similarly on the microphone and speaker side.

<pre>//**********************************************************************************
// MAKE A CALL
//
// BUFFERING CODE BASED UPON:
// <a href="http://jayeshprojects.blogspot.com/2010/04/real-time-mobile-gps-tracker-with.html">  http://jayeshprojects.blogspot.com/2010/04/real-t...>
//
//**********************************************************************************

#include <SoftwareSerial.h>
#define BUFFSIZ 90

//Set up buffer array
char at_buffer[BUFFSIZ];
char buffidx;

//Network state variables
int network_registered;
int network_AT_ready;

//Code state variables
int firstTimeInLoop = 1;
int firstTimeInOtherLoop = 1;
int x;
 
//Will hold the incoming character from the Serial Port.
char incoming_char=0;

//Create a 'fake' serial port. Pin 2 is the Rx pin, pin 3 is the Tx pin.
SoftwareSerial cell(2,3);  


void setup() {
  
  //Initialize Arduino serial port for debugging.
  Serial.begin(9600);
  
  //Initialize virtual serial port to talk to Phone.
  cell.begin(9600);

  //Hello World.
  Serial.println("Starting SM5100B Communication...");
  delay(1000);

  //Set initial network state
  network_registered = 0;
  network_AT_ready = 0;

}


//Read AT strings from the cellular shield
void readATString(void) {

  char c;
  buffidx= 0; // start at begninning
  for (x = 0; x < 10000; x ++) {    
    if(cell.available() > 0) {
      c=cell.read();
      if (c == -1) {
        at_buffer[buffidx] = '\0';
        return;
      }
      if (c == '\n') {
        continue;
      }
      if ((buffidx == BUFFSIZ - 1) || (c == '\r')){
        at_buffer[buffidx] = '\0';
        return;
      }
      at_buffer[buffidx++]= c;
    }
  }
}




//Process the AT strings
void ProcessATString() {

  if( strstr(at_buffer, "+SIND: 8") != 0 ) {
    network_registered = 0;
    Serial.println("network Network Not Available");
  }

  if( strstr(at_buffer, "+SIND: 11") != 0 ) {
    network_registered=1;
    Serial.println("network Registered");
  }
  
  if( strstr(at_buffer, "+SIND: 4") != 0 ) {
    network_AT_ready=1;
    Serial.println("network AT Ready");
  }
}

 
void loop() {

/* If called for the first time, loop until network and AT is ready */

if(firstTimeInLoop == 1) {

  firstTimeInLoop = 0;
  while (network_registered == 0 || network_AT_ready == 0) {
    readATString();
    ProcessATString();
    }
  }

//LET'S MAKE A PHONE CALL!
if(firstTimeInOtherLoop == 1){
  
     //Change the 10 digit phone number to whatever you wish
     cell.println("ATD4155551212");
     firstTimeInOtherLoop = 0;
   }
}

<pre>//**********************************************************************************
// ANSWER A CALL
//
// BUFFERING CODE BASED UPON:
// <a href="http://jayeshprojects.blogspot.com/2010/04/real-time-mobile-gps-tracker-with.html">  http://jayeshprojects.blogspot.com/2010/04/real-t...>
//
//**********************************************************************************

#include <SoftwareSerial.h>
#define BUFFSIZ 90

//Set up buffer array
char at_buffer[BUFFSIZ];
char buffidx;

//Network state variables
int network_registered;
int network_AT_ready;

//Code state variables
int firstTimeInLoop = 1;
int firstTimeInOtherLoop = 1;
int x;
 
//Will hold the incoming character from the Serial Port.
char incoming_char=0;

//Create a 'fake' serial port. Pin 2 is the Rx pin, pin 3 is the Tx pin.
SoftwareSerial cell(2,3);  


void setup() {
  
  //Initialize Arduino serial port for debugging.
  Serial.begin(9600);
  
  //Initialize virtual serial port to talk to Phone.
  cell.begin(9600);

  //Hello World.
  Serial.println("Starting SM5100B Communication...");
  delay(1000);

  //Set initial network state
  network_registered = 0;
  network_AT_ready = 0;

}


//Read AT strings from the cellular shield
void readATString(void) {

  char c;
  buffidx= 0; // start at begninning
  for (x = 0; x < 10000; x ++) {    
    if(cell.available() > 0) {
      c=cell.read();
      if (c == -1) {
        at_buffer[buffidx] = '\0';
        return;
      }
      if (c == '\n') {
        continue;
      }
      if ((buffidx == BUFFSIZ - 1) || (c == '\r')){
        at_buffer[buffidx] = '\0';
        return;
      }
      at_buffer[buffidx++]= c;
    }
  }
}




//Process the AT strings
void ProcessATString() {

  if( strstr(at_buffer, "+SIND: 8") != 0 ) {
    network_registered = 0;
    Serial.println("network Network Not Available");
  }

  if( strstr(at_buffer, "+SIND: 11") != 0 ) {
    network_registered=1;
    Serial.println("network Registered");
  }
  
  if( strstr(at_buffer, "+SIND: 4") != 0 ) {
    network_AT_ready=1;
    Serial.println("network AT Ready");
  }
}

 
void loop() {

/* If called for the first time, loop until network and AT is ready */

if(firstTimeInLoop == 1) {

  firstTimeInLoop = 0;
  while (network_registered == 0 || network_AT_ready == 0) {
    readATString();
    ProcessATString();
    }
  }

if(firstTimeInOtherLoop == 1){
  //Look for incoming call
  if( strstr(at_buffer, "+CPAS: 3") != 0 ) {
     //Answer the phone
     cell.println("ATA");
     firstTimeInOtherLoop = 0;
   }
 }
}