Gsm module SIM900 interfacing with arduino

Learn to interface GSM module with arduino uno to send or recieve messages and to dial a number with AT commands.

In this section, we will learn How to interface GSM module sim900 interfacing with arduino using softserial library, and code to control lights by sending sms to your sim module.

SIM900A module work on AT commands. AT commands are instructions used to control a modem and is the abbreviation of  ‘attention’. some of AT commands are listed below, we will use these command in our Arduino code.

To check modem:                               AT
To change sms sending mode:        AT+CMGF=1
Make a voice call:                              ATD +91Mobilenumber
To send New SMS:                            AT+CMGS=”MOBILE NO” “MESSAGE”  “^z”
To disconnect a call:                         ATH
To recieve incoming call:                 ATA
To redial last number:                      ATDL
To set a particular baud rate:          AT+IPR=?         (To view the baud rate values)
AT+IPR=0         (To set the modem to auto-baud mode)

Materials required

Arduino uno
max232 for serial output
GSM module (SIM900A in my case)
Relay (to control output)

Source Code :