GSM Sim900A with Arduino Complete Guide with GSM based Projects Examples

(Last Updated On: February 28, 2020)

GSM Sim900A

GSM Sim900A Description:

GSM Sim900A– the GSM SIM900A by the SIMCom is designed for global market, SIM900A is a dual-band GSM/GPRS engine that works on frequencies EGSM 900MHz and DCS 1800MHz. SIM900A 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 24mm x 24mm x 3mm, SIM900A can meet almost all the space requirements in your applications, such as M2M, smart phone, PDA and other mobile devices.

GSM Sim900A

The physical interface to the mobile application is a 68-pin SMT pad, which provides all hardware interfaces between the module and customers’ boards.

The SIM900A is designed with power saving technique so that the current consumption is as low as 1.5mA in SLEEP mode.

The SIM900A is integrated with the TCP/IP protocol; extended TCP/IP AT commands are developed for customers to use the TCP/IP protocol easily, which is very useful for those data transfer applications.


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SIM900A key features:

GSM Sim900A

GSM SIM900A Functional Diagram:

GSM Sim900A

The above figure shows a functional diagram of the SIM900A and illustrates the mainly functional parts:

  • The GSM baseband engine
  • Flash and SRAM
  • The GSM radio frequency part
  • The antenna interface
  • The Other interfaces

GSM SIM900A Pin Description:

GSM Sim900A

GSM SIM900A by the SIMCom is a 68 terminal device as shown in the pin diagram given above. I will describe the function of each pin.

Pin Number Pin Name Description
1 PWRKEY Voltage input for PWRKEY.  PWRKEY should be pulled low to power on or power off the system.

The user should keep pressing the key for a short time when power on or power off the system because the system need margin time in order to assert the software.

2 PWRKEY_OUT Connecting PWRKEY and PWRKEY_OUT for a short time then release also can power on or power off the module.
3 DTR Data terminal Ready  [Serial port ]
4 RI Ring indicator  [Serial port ]
5 DCD Data carry detect  [Serial port ]
6 DSR Data Set Ready  [Serial port ]
7 CTS Clear to send [Serial port ]
8 RTS Request to send [Serial port ]
9 TXD Transmit data [Serial port ]
10 RXD Receive data [Serial port ]
11 DISP _CLK Clock for display [Display interface]
12 DISP_DATA Display data output [Display interface]
13 DISP _D/C Display data or command select [Display interface]
14 DISP _CS Display Enable [Display interface]
15 VDD_EXT 2.8V output power supply
16 NRESET External reset input
17,18,29,39,45,

46,53,54,58,59,

61,62,63,64,65

GND Ground
19 MIC_P Microphone Positive
20 MIC_N Microphone Negative
21 SPK_P Speaker Positive
22 SPK_N Speaker Negative
23 LINEIN_R Right Channel input [External line inputs are available to directly mix or multiplex externally generated analog signals such as polyphonic tones from an external melody IC or music generated by an FM tuner IC or module.]
24 LINEIN_L

 

Left Channel Input
25 ADC General purpose analog to digital converter.
26 VRTC Current input for RTC when the battery is not supplied for the system.

Current output for backup battery when the main battery is present and the backup battery is in low voltage state.

27 DBG_TXD Transmit pin [Serial interface for debugging and firmware upgrade ]
28 DBG_RXD Receive pin [Serial interface for debugging and firmware upgrade ]
30 SIM_VDD Voltage supply for SIM card
31 SIM_DATA SIM data output
32 SIM_CLK SIM clock
33 SIM_RST SIM reset
34 SIM_PRESENCE SIM detect
35 PWM1 PWM Output
36 PWM2 PWM Output
37 SDA Serial Data [I2C]
38 SCL Serial Clock [I2C]
40,41,42,43,44

&

47,48,49,50,51

KBR0 to KBR4

&

KBC4 to KBC0

Keypad interface  [ROWS & COLUMNS]
52 NETLIGHT Indicate net status
55,56,57 VBAT Three VBAT pins are dedicated to connect the supply voltage. The power supply of SIM900A has to be a single voltage source of VBAT= 3.4V to 4.5V. It must be able to provide sufficient current in a transmit burst which typically rises to 2A.
60 RF_ANT Antenna connection
66 STATUS Indicate working status
67 GPIO 11 General Purpose Input/output
68 GPIO 12 General Purpose Input/output


GSM SIM900A Applications

  • Cellular Communication
  • Home Automations
  • Security based projects
  • Sensors monitoring
  • Robotics
  • Mobile Phone Accessories
  • Servers
  • Computer Peripherals
  • Automobile
  • USB Dongles

How to use the SIM900A:

GSM Sim900A

It’s seems quite impossible for a beginner to do all the soldering, I will never do this, in fact I don’t have to do this, because readymade modules are already available in the market.

GSM Sim900A Module:

GSM Sim900A

This is the GSM Sim900A mini Module. The first thing that you will notice about this GSM module is that, it has no onboard voltage regulator, so be very careful while applying the voltage; Because voltages greater than 5 volts can easily damage this module. Ideal voltage for this GSM module is 4.7v but you can easily power up this GSM Sim900A module using a 5v adaptor. if you don’t have a 5v adaptor then you can make your power supply using lm317t adjustable variable voltage regulator, I have a very detailed tutorial on lm317t explaining everything.

There are a few things that I really like about the GSM sim900A module which are

  1. This is the cheapest GSM module available on the Market.
  2. Another cool thing is, it can be easily interfaced with 5V supported controller boards like Arduino Uno, Arduino mega, Arduino Nano etc and also with 3.3v controller boards like Nodemcu ESP8266 Wifi Module and ESP32 etc. The GSM Sim900A module interfacing with Nodemcu ESP8266 and ESP32 will be explained in one of my future articles.


GSM Sim900A specifications:

GSM Sim900A Power Supply:

As I said earlier the GSM Sim900A Module has no onboard voltage regulator. Although it has a power supply pin which can be connected with the Arduino’s 5 volts. When no sensors are connected with the Arduino then you can Run this GSM module without any problem. But the time you start connecting different sensors with the Arduino, then Arduino cannot provide enough current to the Sim900A Module due to which the Arduino starts resetting.

So, my recommendation is use an external regulated 5v power supply.

GSM Sim900A pin configuration:

GSM Sim900A

The white connector labeled with 4.7 – 5V, This is where we connect the external 5volt regulated power supply. It has a total of 9 male headers. The three male headers on the right side are not connected.

  • Pin number 1 is the VCC which can be connected with the Arduino’s 5volts. In my case as I will power up this module using the external power supply so I will leave this pin unconnected.
  • Pin number 2 is the ground, which will be connected with the Arduino’s ground.
  • Pin number 3 is the 5v TXD,
  • Pin number 4 is the 5v RXD,
  • Pin number 5 is the 3.3v TXD, and
  • Pin number 6 is the 3.3v RXD.


GSM Sim900A AT commands:

TO CHECK THE MODEM:

AT

OK

TO CHANGE SMS SENDING MODE:

AT+CMGF=1

OK

TO SEND NEW SMS:

AT+CMGS=”MOBILE NO.”

<MESSAGE

{CTRL+Z}

PREFERRED SMS MESSAGE STORAGE:

AT+CPMS=?

+CPMS: (“SM”),(“SM”),(“SM”)

OK

AT+CPMS?

+CPMS: “SM”,19,30,”SM”,19,30,”SM”,19,30



TO MAKE A VOICE CALL:

ATD923339348223;

TO REDIAL LAST NO:

ATDL

TO RECEIVE INCOMING CALL:

ATA

TO HANGUP OR DISCONNECT A CALL:

ATH

OPERATOR  SELECTION:

AT+COPS=?

OK

AT+COPS?

+COPS: 0,0,”AirTel”

OK

TO SET A PARTICULAR BAUDRATE:

AT+IPR=?         {To view the baud rate values}

AT+IPR=0         {To set the modem to autobauding mode}

READ OPERATOR NAMES.

AT+COPN=?

OK

AT+COPN

+COPN: “472001”,”DHIMOBILE”

+COPN: “60500

+COPN: “502012”,”maxis mobile”

+COPN:

+COPN: “502013”,”TMTOUCH”

+COPN

+COPN: “502016”,”DiGi”

+COPN: “502017”,”TIMECel””

+COPN: “502019”,”CELCOM GSM”


AT+CRC SET CELLULAR RESULT CODES FOR INCOMING CALL INDICATION:

AT+CRC=?

+CRC: (0-1)

OK

AT+CRC?

+CRC: 0

OK

AT+CRC=1

OK

+CRING: VOICE

GPRS COMMANDS:

Command Description

AT+CGATT                   ATTACH/DETACH FROM GPRS SERVICE

AT+CGDCONT              DEFINE PDP CONTEXT

AT+CGQMIN               QUALITY OF SERVICE PROFILE (MINIMUM ACCEPTABLE)

AT+CGQREQ               QUALITY OF SERVICE PROFILE (REQUESTED)

AT+CGACT                PDP CONTEXT ACTIVATE OR DEACTIVATE

AT+CGDATA               ENTER DATA STATE

AT+CGPADDR              SHOW PDP ADDRESS

AT+CGCLASS              GPRS MOBILE STATION CLASS

AT+CGEREP               CONTROL UNSOLICITED GPRS EVENT REPORTING

AT+CGREG                NETWORK REGISTRATION STATUS

AT+CGSMS                SELECT SERVICE FOR MO SMS MESSAGES

AT+CGCOUNT              GPRS PACKET COUNTERS


GSM Sim900A with Arduino:

Following are some of the projects which explain GSM Sim900A interfacing with Arduino and GSM Sim900A Arduino Code.

Following are the detailed GSM Sim900A based projects.

Arduino Fire Alarm System with GSM Alert Text Message & Buzzer

Arduino Fire Alarm System with GSM Alert Text Message & Buzzer

Flood Monitoring System with SMS Alert using Arduino and GSM

Flood Monitoring System with SMS Alert using Arduino and GSM


Door Lock System using Arduino and GSM, Wireless Electronic Lock

Door Lock System using Arduino and GSM, Wireless Electronic Lock

Door Opening GSM alarm Wireless home security system using Arduino

Door Opening GSM alarm Wireless home security system using Arduino


How to use GSM and Bluetooth Together To monitor Any Sensors wirelessly using Arduino

How to use GSM and Bluetooth Together To monitor Any Sensors wirelessly using Arduino

RFID & GSM based student Attendance Alert message to parents

RFID & GSM based student Attendance Alert message to parents

Arduino GSM Project: Security Alert message to multiple numbers

Arduino GSM Project: Security Alert message to multiple numbers


Request Temperature Data Using GSM and Arduino

Request Temperature Data Using GSM and Arduino

Arduino and Gsm based laser security system

Arduino and Gsm based laser security system



Car accident location tracking using GSM, GPS, and Arduino

Car accident location tracking using GSM, GPS, and Arduino

GSM Alarm System Using Arduino and a PIR Sensor

GSM Alarm System Using Arduino and a PIR Sensor

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About the Author: Engr Fahad

My name is Shahzada Fahad and I am an Electrical Engineer. I have been doing Job in UAE as a site engineer in an Electrical Construction Company. Currently, I am running my own YouTube channel "Electronic Clinic", and managing this Website. My Hobbies are * Watching Movies * Music * Martial Arts * Photography * Travelling * Make Sketches and so on...

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