1.    Test GPRS ON Sim900:

     To test the GPRS as well as test other functions on the Sim900, the first thing to prepare is a Sim900 module, a USB to UART computer connection circuit, a 3.3V LM2596 STEP DOWN and PC terminal software. test guide Sim900 module)


Step 1: Boot Module:


      Start Sim900 module is completed we will receive the message on the terminal as follows ...





Step 2: Check the connection:


      After the boot is complete we check the connection between the Sim900 and the PC. From the terminal on the PC type AT command, if successfully connected Sim900 will return OK

    From this step we start to configure the GPRS for Sim900, to understand the sequence of steps you can refer to AT command set about GPRS.


Step 3: Register GPRS for sim:

 It is important you have to determine the sim you use registered GPRS with the network or not? If you have registered, you can skip this step and follow the next steps.

       The GPRS registration order is:



      APN, username and password are dependent on the network you use, for example some popular cellular networks in Vietnam


















Vietnam mobile











     For example, the GPRS registration command on the mobifone network is as follows:

 >> AT+CIPCSGP=1,”m-wap”,”mms”,”mms”

<< OK

       There are many ways to configure GPRS for the Sim900 with AT Command provided by SIMCom, AT-COM introduces you to the configuration, you can develop your own configuration as long as you can. The operation is stable.

 Step 4: Disconnect GPRS:

       To ensure stable operation for the Sim900 during GPRS connection we need a disconnect from the beginning to prevent the Sim from being connected. The disconnected command has the following syntax:


       If the command is successful we are on the terminal screen as follows:



 Step 5: Start connecting to the server:

       Starting to connect to the server, from here we can confirm that the GPRS configuration is successful or not. The execution order has the following syntax:

                                                  AT+CIPSTART=”MODE”,”Domain name/IP address”,”port”

       Mode here is that the connection protocol can be TCP or UDP

       Domain name / IP address is the domain name of the server or IP of the server depending on the connection of each person

       Port is the port that the server allows to connect to.

       For example, a sample command connected to google on port 80 is as follows:

>> AT+CIPSTART=”TCP”,”google.com.vn”,”80”


      If successful, the server will respond CONNECT OK

      From here it can be seen that the GPRS test completed we can also test the data transfer to the server by command with the following syntax:


      After typing the AT + CIPSEND command, followed by the message body and finally send the message with the key combination Ctrl + Z.

       For example sending a string to google as follows:


 <<  >

 >> GET / HTTP/1.1

 >>Host: www.google.com

 >>Connection: Keep-Alive

 >>Accept: */*

 >>Accept-Language: en-us


 << // the server's data will be received here //

 The following is the result on the terminal performs the entire GPRS Sim900 test process:





2. GPRS application to transfer data to PC:

    AT-COM introduces you to a GPRS application for sending data to a PC. The request is to use the Sim900's GPRS transmission line to send analog data to a PC using the microcontroller.

Circuit diagram of the whole circuit:



      Client block principle diagram:




      Source block diagram:




      Practical picture of whole circuit:



      In order for the server to receive data sent by the client, a server program should be used to handle that. AT-COM introduces a server program provided by SIMCom.