Need Help with SIM900 GSM Module

Hi,

I need help with the following:

I am creating a product wherein a person can control electrical appliances via remote SMS.

I want to SWITCH ON & SWITCH OFF electrical appliance with remote sms.

Here I am using four hardware:

1. A tubelight as electrical appliance.
2. Microcontroller AT89S52 of 8051 Family to intrepret received SMS and take action accordingly (On/Off).
3. SIM900 GSM Module to receive SMS from GSM Mobile and pass it to Microcontroller.
4. GSM Mobile Phone to send SMS.

SMS Formats:

1. "ON" to switch on.
2. "OFF" to switch off.

I have mounted the hardware properly and can ring the SIM latched on the SIM900 GSM Module.

But further I am stuck:

1. When I am sending SMS to SIM900 GSM Module ... I don't know how to pass the received SMS to Microcontroller.

2. And what shall be the format of communication between SIM900 GSM Module and Microcontroller AT89S52 of 8051 Family.

Any help, advice or guidance needed urgently.

Thx & Rgds

Nivesh Sharma - Electronics Engineer

Hello,
What you need to do is use the USART of your microcontroller to monitor RX of module, when it receives any message your programmed function will store it in buffer and bring it to u manipulate it as desired.
I do not know if u have experience in programming microcontrollers, but you can search for examples, it is easy and you will find lots of information on the internet.

@Nivesh,

It is a simple UART communication..Only you need to confirm the baud rate of SIM900 as whether it is 9600,8,N,1 or 115200,8,N,1.

The default baud rate will be 115200,8,N,1. Try communicating only with the hyperterminal...i.e.Connect the module to your laptop and try to communicate or execute the AT commands in hyperterminal first...Get a first and then proceed further to interface with the MCU..