1. Introduce the SIM900

  SIMCom Introduces The SIM900 is an extremely compact GSM / GPRS module designed for the global market. The SIM900 works in quad band GSM 850MHz, EGSM 900MHz, 1800MHz DCS and 1900MHz PCS as a terminal with a powerful single-core processor, enhancing key features based on the processor. The ARM926EJ-S, giving you the benefits of compact size (24x24 mm), meets the space requirements of M2M applications.




2. Test Breakout SIM900

  Before starting the test, you need a 3.2-4.8V - 3A power supply for Breakout sim900, AT-COM has researched and developed LM2576 STEP DOWN





and board communicate with the computer  USB to UART 




3. Diagram connecting computer with Break900 SIM900



We use the Terminal software to communicate with the Break900 SIM900

Terminal software interface as follows:




Breakout SIM900 test steps:


Step 1: Start SIM900

- After starting SIM900 we will see on the screen as follows ...




- The screen shows the 4 lines as above, ie the SIM900 has finished booting.


Step 2: Test the transmission line

  - To test the transmission, we send the AT command to the sim you type from the AT keyboard and press enter. At the same time, the screen will display:



- If you receive an OK message, the transmission is good.


Step 3: Test the call:

   - After successful AT test, we use another phone to call sim card on the SIM900 breakout to test the call.

SIM900 works fine and returns the screen as follows:



Step 4: Test to receive the message

First of all, we have to configure the message of SIM900 in text format

The command structure is as follows: AT + CMGF = 1 Type Enter

Now we will use another phone to send a message to SIM900. If the SIM900 works well, it will receive the following sequence:




Step 5: Test call

  - The next step is to test the sim to make a call using the command:

Command syntax: ATDxxxxxxxxxx; Type Enter (xxxxxxxxxxx: the phone number to call)

If you want to end the call using the ATH command to end the call.

  Command syntax: ATH Type Enter

Remember to hit the ATDxxxxxxxxxx command line afterwards; Type Enter followed by pressing Ctrl + z, the new sim will understand and make the call.



Step 6: Test the message

- To test message use command

  AT + CMGS = "xxxxxxxxxxx" (xxxxxxxxxxx: is the phone number needed for IM)

  > message content

- After entering the message content and finally the key combination Ctrl + z to simulate and send the message. Here are the steps:



- Sim returns an OK message successfully sent.


Step 7: Test the account:

- To check your account use ATD * 101 # for prepaid sim and

Command syntax: ATD * 112 # for sim pay later.