Send sms using gsm module and pic microcontroller : this article explains how to send sms using gsm module and pic microcontroller. what is AT commands and their use to send and receive sms. I have already posted a article on gsm module interfacing with pic microcontroller. I suggest you to go through that article before proceeding in this that you may get an idea about gsm module SIM900D, its features and interfacing circuitry.

What are AT command?

AT commands are used to initialize whatever you want gsm module to do for you. SIMCOM a company of sim tech have a AT command complete document for SIM900. You can easily download it from google. For each SIM900D feature there are separate AT command available. User can easily use these commands to configure whatever functionality they want to use from gsm module available features. In this article I will discuss only AT commands use to send sms. But you will get an idea how to use rest of AT commands for using other features of gsm module. AT commands you need to know for sending sms through gsm module SIM900D and how to use while writing code:



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For example we want to send SMS “Welcome to”.

  1. AT+CMGF

There are two modes to send sms in gsm 1) in text mode  2) PDU in binary format but it is easier to send sms using text mode. To set gsm to text mode :

AT+CMGF = 1;


This command is used to selest character mode and set gsm character mode to



This command is used to select number of message recipient and message you wan to send to recipient.To select number and message follow the following procedure :

AT+CMGS = “+090078601”

when you send this command to modem, modem will respond you with greater than mark “>”. After that sign write your message you want to send to recipient and terminate your message with control+z in character form.I will show you in code how to write control+z in character form.

Above commands are necessary command to send sms through gsm module SIM900D. Below is a list of optional AT commands use to send sms :

  • AT + CSCA  is used to set message center number of sim which you are inserted in gsm module sim jacket
  • AT + CSMP  is used to set parameters of text mode


To know more about AT commands for SMS and their details, go through data sheet of AT commands by SIMCOM.