GSM – SIM900A

Description

GSM/GPRS Modem-RS232 is built with Dual Band GSM/GPRS engine- SIM900A, works on frequencies 900/ 1800 MHz. The Modem is coming with RS232 interface,which allows you connect PC as well as microcontroller with RS232 Chip(MAX232). The baud rate is configurable from 9600-115200 through AT command. The GSM/GPRS Modem is having internal TCP/IP stack to enable you to connect with internet via GPRS. It is suitable for SMS, Voice as well as DATA transfer application in M2M interface.

gsm1_Sim900A GSM - SIM900A

gsm2_sim900A GSM - SIM900A


The onboard Regulated Power supply allows you to connect wide range unregulated power supply . Using this modem,you can make audio calls, SMS, Read SMS, attend the incoming calls and internet ect through simple AT commands

GSM/GPRS Modem Fetures 

  • High Quality Product (Not hobby grade)
  • Dual-Band GSM/GPRS 900/ 1800 MHz
  • RS232 interface for direct communication with computer or MCU kit
  • Configurable baud rate
  • Wire Amntenna ( SMA connector with GSM Antenna Optional )
  • SIM Card holder.
  • Built in Network Status LED
  • Inbuilt Powerful TCP/IP protocol stack for internet data transfer over GPRS.
  • Normal operation temperature: -20 °C to +55 °C
  • Input Voltage: 12V DC

Important Notes

1. We use SIM900 GSM Module – This means the module supports communication in 900MHz band. We are from India and most of the mobile network providers in this country operate in the 900Mhz band. If you are from another country, you have to check the mobile network band in your area. A majority of United States mobile networks operate in 850Mhz band (the band is either 850Mhz or 1900Mhz). Canada operates primarily on 1900 Mhz band.

2. Check the power requirements of GSM module – GSM modules are manufactured by different companies. They all have different input power supply specs. You need to double check your GSM modules power requirements. In this tutorial, our gsm module requires a 12 volts input. So we feed it using a 12V,1A DC power supply. I have seen gsm modules which require 15 volts and some other which needs only 5 volts. They differ with manufacturers. If you are having a 5V module, you can power it directly from Arduino’s 5V out.

BOOTING UP THE GSM

1. Insert the SIM card to module and lock it.

2. Connect the adapter to module and turn it ON!

3. Now wait for some time (say 1 minute) and see the blinking rate of ‘status LED’ (GSM module will take some time to establish connection with mobile network)

4. Once the connection is established successfully, the status LED will blink continuously every 3 seconds.

Connections

In this picture i have mentioned how to connect the GSM with any microcontrollers. 

Connection_gsm GSM - SIM900A

If you are giving different power supply from different source (socket or adapter)  like above you should connect the common ground. Otherwise no need to give common ground. 

Basic Commands

There are lots of commands used for GSM. Here we are going to use few commands. 

TO CHECK THE MODEM:

Send – AT

Receive – OK

TO CHANGE SMS SENDING MODE:

Send – AT+CMGF=1

Receive – OK

TO SEND NEW SMS:

Send – AT+CMGS=”MOBILE NO”

Send – <MESSAGE> “Your message”

Send – {CTRL+Z}  (0x1A)

TO MAKE A VOICE CALL:

Send – ATD0123456789  (0123456789 – Dial number)

TO REDIAL LAST NO:

Send – ATDL

TO RECEIVE INCOMING CALL:

Send – ATA

TO HANGUP OR DISCONNECT A CALL:

Send – ATH

TO SET A PARTICULAR BAUDRATE:

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

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

If you want all commands please download the Commands Here. Thank you.

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