GSM Interfacing with 8051 Microcontroller

Mobile communication is an emerging technology these days. GSM is the acronym for Global System for Mobile Communication. GSM module is wireless modem that transmits data using radio waves. GSM architecture is similar to the mobile architecture. GSM modems are generally used in many electronic applications and they are required to interface with the microcontrollers. This article describes interfacing of a GSM modem to an AT89C51 microcontroller.

GSM Interfacing with 8051 Microcontroller Circuit Principle:

The main principle of this circuit is to interface a GSM modem with the microcontroller. The microcontroller used is AT89C51 microcontroller. To communicate with GSM modem, AT commands are required. Microcontroller sends these commands to the GSM modem, which is then activated to perform the required operation.

The following AT commands are frequently used to control the operations of GSM modem.

Command –  Operation

AT+CSMS    –    Select message service.

AT+CMGF   –    Message format.

AT+CMGL   –    List messages.

AT+CMGR   –    Read message.

AT+CMGS   –    Send message.

AT+CMGD   –   Delete message.

ATA              –    Answer a call.

ATD              –   Dial a number.

ATDL            –  Dial the last outgoing number.

ATH             –   Hang up the call.

GSM Modem Interfacing with 8051 Microcontroller Circuit Diagram:

Circuit Components:

• MAX232 IC.
• AT89C51 microcontroller.
• GSM modem.
• Capacitors C1, C2, C3, C4, C5, C6.
• Crystal oscillator.
• Liquid crystal display.
• Potentiometer. 

How to Operate GSM Interfacing with 8051 Microcontroller Circuit?

• Initially, connect the circuit as shown in the circuit 8051 Microcontroller diagram.
• Switch on the power supply.
• Now send a message from any other phone to the SIM present in the GSM module.
• Whenever a message is received by the GSM, it is displayed on the LCD.
• If you want to send a message press the button B1 connected to port B.
• This sends a message written in the code.