CHAPTER 1:

GSM

GSM stands for Global System for Mobile Communications formerly called as Groupe Spcial Mobile.

This is a standard set developed by the European Telecommunications Standards Institute (ETSI) to describe technologies for second generation (or "2G") digital cellular networks. The GSM standard initially was used originally to describe switched circuit network for full duplex voice telephony to replace first generation analog cellular networksThe standard was expanded over time to include first circuit switched data transport, then packet data transport via GPRS(General packet radio service). Packet data transmission speeds were later increased via EDGE. The GSM standard is succeeded by the third generation (or "3G") UMTS standard developed by the 3GPP. GSM networks will evolve further as they begin to incorporate fourth generation (or "4G") LTE Advanced standards. "GSM" is a trademark owned by the GSM Association.

GSM networks operate in a number of different carrier frequency ranges (separated into GSM frequency ranges for 2G and UMTS frequency bands for 3G), with most 2G GSM networks operating in the 900MHz or 1800MHz bands. Where these bands were already allocated, the 850MHz and 1900MHz bands were used instead (for example in Canada and the United States). In rare cases the 400 and 450MHz frequency bands are assigned in some countries because they were previously used for first-generation systems.

IndiaGSM 9005 carriers

GSM 900/18003 carriers

Regardless of the frequency selected by an operator, it is divided into timeslots for individual phones to use. This allows eight full-rate or sixteen half-rate speech channels per radio frequency. These eight radio timeslots (or eight burst periods) are grouped into a TDMA frame. Half rate channels use alternate frames in the same timeslot. The channel data rate for all 8 channels is 270.833kbit/s, and the frame duration is 4.615ms.

The transmission power in the handset is limited to a maximum of 2 watts in GSM850/900 and 1 watt in GSM1800/1900

One of the key features of GSM is the Subscriber Identity Module, commonly known as a SIM card. The SIM is a detachable smart card containing the user's subscription information and phone book. This allows the user to retain his or her information after switching handsets. Alternatively, the user can also change operators while retaining the handset simply by changing the SIM. Some operators will block this by allowing the phone to use only a single SIM, or only a SIM issued by them; this practice is known as SIM locking.We are be using SIM300 GSM Module in our Project.SIM300 is a Tri-band GSM/GPRS engine from SIMCOM Ltd., that works on frequencies EGSM 900 MHz, DCS 1800 MHz and PCS 1900 MHz. SIM300 features GPRS multi-slot class 10/ class 8 (optional) and supports the GPRS coding schemes CS-1, CS-2, CS-3 and CS-4.

With a tiny configuration of 40mm x 33mm x 2.85 mm , SIM300 can fit almost all the space requirement in an application, such as Smart phone, PDA phone and other mobile device.

The physical interface between SIM300 and the mobile application is through a 60 pins board-to-board connector, which provides all hardware interfaces from module to customers boards except the RF antenna interface.

The keypad and SPI LCD interface will give you the flexibility to develop customized applications.

Two serial ports can help you easily develop your applications.

Two audio channels include two microphones inputs and two speaker outputs. These audio interfaces can be easily configured by AT command.

One ADC input

Two GPIO ports and SIM card detection port

Both 1.8V and 3.0V SIM Cards are supported. The SIM interface is powered from an internal regulator in the module having nominal voltage 2.8V. All pins reset as outputs driving low.

Reference circuit of 6PIN SIM cardYou can use AT Commands "AT" meaning attention , to communicate with the SIM card. The SIM interface supports the functionality of the GSM Phase 1 specification and also supports the functionality of the new GSM Phase 2+ specification for FAST 64 kbps SIM (intended for use with a SIM application Tool-kit).The "AT" or "at" prefix must be set at the beginning of each command line. To terminate a command line enter . Commands are usually followed by a response that includes . Testing and General commands for GSM1. Steps to test the GSM ModuleWe can use the PC Hyper Terminal to interact with the GSM Module.

First insert the SIM card to the GSM Module,

Connect the Serial cable RS232 to the PC via DB9 pin connector on the GSM Module.

Give the power supply. The power supply indicating LED will be ON continuously.

Another LED on the Module starts blinking to indicate the availability of network.

If the network is available then the delay between the blinking is less.

If the network is not available then the delay between the blinking is more.

Each GSM modem will have a unique id called IMEI.

Open Hyper Terminal in the PC , apply the below settings

Connect using(COM1

Bits per second(9600

Data bits

(8

Parity

(None

Stop bits

(1

Flow control

(None Type AT on HyperTerminal and press ENTER ( OK will be display as a response from the GSM Module.

AT

OK

Below are few more commands and response from the Module

AT+CGMI - To check Manufacturer Identification

FLYFOT M260 MODEM

OK

AT+CGMM

MULTIBAND 900 1800 1900

OK

2. Commands in detailA . Manufacturer identification +CGMI

Description:

This command gives the manufacturer identification.Syntax:

Command syntax: AT+CGMI

B. New message indication +CNMI

Description:

This command selects the procedure for message reception from the network.Syntax :

Command syntax : AT+CNMI=,,,,

C. Send message +CMGS

Description :

The field is the address of the terminal to which the message is sent. To send the message, simply type, character (ASCII 26). The text can contain all existing characters except and (ASCII 27). This command can be aborted using the character when entering text. In PDU mode, only hexadecimal characters are used (09,AF).

Syntax :Command syntax in PDU mode :

AT+CMGS=

PDU is entered

The message reference, , which is returned to the application is allocated by the product. This number begins with 0 and is incremented by one for each outgoing message (successful and failure cases); it is cyclic on one byte (0 follows 255).3. Few Worked Examples

Command to send SMSAT+CMGS="9845843843"

> HI

+CMGS: 9

OK

at+cpin?

// To check network connectivity

+CPIN: READY

AT+COPS?

+COPS: 0,0,"Hutch-Kamataka"

AT&F

// To store Factory default

OK

// Use the next 2 commands if we face any problem to send and receive SMS.

// If we type SMS send command, then error comes.

// If we enable in SMS receive command, then the SMS received will be in numbers and alphabets format.

AT+CMGF=1

OK

AT+CMGR=1

+CMGR: "REC READ","+919880147756",,"10/03/08,17:48:53+22"

Ok

Command to set in receive mode

AT+CNMI=2,2,0,0,0

OK

+CMT: "+919845843843",,"10/05/12,08:18:40+22"

// Total 45 characters

SYSTEM STARTS

AT+CNMI=2,2,0,0,0

OK

+CMT: "+919845843843",,"09/12/25,23:44:42+22"

Hello

List of other SIM 300 AT Commands in DetailAT+CBC? - To check for Battery StarusAT+CBC=?

AT+CBC

AT+CBC=1

0: battery not in charge

1: battery in charge

2: battery full

3: battery low

0: battery level 0

25: battery level 1

50: battery level 2

75: battery level 3

100: battery level 4+CBC: n,m

OK

+CBC: (0-3), (0-100)

OK

+CBC: n,m

OK

+CME ERROR 3

Note: not support

AT+CGMIThis command gives the manufacturer identification.

AT+CGMI

Note: Get manufacture identification

AT+CGMI=?

AT+CGMI?

AT+CGMI=1FLYFOT MODEM

OK

Note: Command valid, FLYFOT modem

OK

+CME ERROR 3

Note: not support

AT+CPASThis command returns the activity status of the mobile equipment.

AT+CPAS

Note :Current activity status

AT+ CPAS?

AT+ CPAS=?

AT+ CPAS=1

0: ready (allow commands from TA/TE)

1: unavailable (does not allow commands)

2: unknown

3: ringing (ringer is active)

4: call in progress

5: asleep (low functionality)+CPAS:

OK

+CME ERROR 3

Note: not support

AT+CMGS= The field is the address of the terminal to which the message is sent. To send the message, simply type,

AT+CMGS=.28.

0031000BA13105119226F40000AD0AA8C3F6

30885E9ED301 +CMGS:

OK

Note : Successful transmission

AT+CNMI=,,,,This command selects the procedure for message reception from the network.

AT+CNMI=2,1,0,0,0

Note : =1

AT+CNMI=2,2,0,0,0

Note : =2

AT+CNMI=2,0,0,1,0

Note : =1

AT+CNMI=2,0,0,0,0

Note : =0

at+cnmi?

Note : Read

at+cnmi=? : controls the processing of unsolicited result codes

Important note: only =2 is supported.

: sets the result code indication routing for SMS-DELIVER indications.

: defines the rules for storing the received CBMs (Cell Broadcast Message) types.

for SMS-STATUS-REPORTs. Default is 0.

Default is 0.OK

Note: message received and saved in sim, then route the SMS-DELIVERS with unsolicited result codes: +CMTI: SM,

OK

Note: message received, then route the

SMS-DELIVERS with unsolicited result codes: +CMT: [,]

OK

Note: SMS-STATUS-REPORTS are routed using unsolicited code:

+CDS :

OK

Note: No SMS-STATUS-REPORTs are routed.

+CNMI: 2,2,0,1,0

Will return the previous status.

+CNMI: (0-3),(0-3),(0-3),(0-1),(0,1)

AT+CMGR=This command allows the application to read stored messages

AT+CMGR=1

Note : Read the message+CMGR: 1,,24

0891683108100005F0040D91683185716393

F900005001429042802304B0182C06

OK

AT+CMGL=This command allows the application to read stored messages, by indicating the type of the message to read.

Does not work. possible values

received unread messages(0)

received read messages(1)

stored unsent messages(2)

stored sent messages(3)

all messages(4)

AT+CMGS= The field is the address of the terminal to which the message is sent. To send the message, simply type,

AT+CMGS=.28.

0031000BA13105119226F40000AD0AA8C3F6

30885E9ED301 +CMGS:

OK

Note : Successful transmission

Interfacing the GSM Module with Microcontroller . A SIM card is inserted to the GSM module. After checking as shown in the steps above, RS232 cable is directly connected between DB9 of the module and the DB9 on the controller port. This establishes the serial communication between them. The GSM commands embedded in the controller takes care to communicate with the GSM Module via RS232 cable-MAX232-Serial I/O pins of the Controller.

MAX232

GSM Send SMS Flow Chart

Initialize using AT Enter command Use ASCII value of Enter = 0x0D

Test GSM Module after inserting SIM as shown in steps above and connect it to the Controller

Command Format AT+CMGS=mob num Enter ( which will transmitted serially to GSM module through UART0 of the Controller

Send AT+CMGS= String

Send 0x22(ASCII value of )

Send Mobile number

Send 0x22(ASCII value of )

Send 0x0D(ASCII value of carriage return)