Basic AT commands for GSM Modem

June 30, 2012 — 1 Comment

A GSM modem is a wireless modem that works with a GSM wireless network. A wireless modem behaves like a dial-up modem. The main difference between them is that a dial-up modem sends and receives data through a fixed telephone line while a wireless modem sends and receives data through radio waves.

     A GSM modem can be an external device or a PC Card / PCMCIA Card. Typically, an external GSM modem is connected to a computer through a serial cable or a USB cable. A GSM modem in the form of a PC Card / PCMCIA Card is designed for use with a laptop computer. It should be inserted into one of the PC Card / PCMCIA Card slots of a laptop computer.
     Like a GSM mobile phone, a GSM modem requires a SIM card from a wireless carrier in order to operate. As mentioned in earlier sections of this SMS tutorial, computers use AT commands to control modems. Both GSM modems and dial-up modems support a common set of standard AT commands. You can use a GSM modem just like a dial-up modem.

In addition to the standard AT commands, GSM modems support an extended set of AT commands. These extended AT commands are defined in the GSM standards. With the extended AT commands, you can do things like:
  • Reading, writing and deleting SMS messages.
  • Sending SMS messages.
  • Monitoring the signal strength.
  • Monitoring the charging status and charge level of the battery.
  • Reading, writing and searching phone book entries.
The number of SMS messages that can be processed by a GSM modem per minute is very low — only about six to ten SMS messages per minute.

Connect your GSM modem to Serial modem of the PC.  Open Hyper Terminal window on PC (Start -> All program -> Accessories -> Communications -> Hyper Terminal)

Open the new connection with default settings and get response from GSM modem on terminal. Once confirmation of GSM modem detection type the following basic commands to use your GSM modem.

Basic AT(attention) commands for GSM modem:

  • AT (Attention command)
  • AT+CREG? (To check signal)
  • AT+CMGS=”” (To send sms)
  • AT+CMGR= (To read sms)
  • AT+CMGD= (To delete sms)
  • ATD98414XXXXX; (To make call)

Implement the same concept in microcontrollers to send AT commands to serial via microcontroller. So that you can control your applications / appliances using mobile with the help of Microcontorllers.




One response to Basic AT commands for GSM Modem

  1. Kindly help me how to make a call using usb modem using AT Command, using ATSMS Library i can able to give call by call method, phone received the call but in pc I can’t able to here the sound of dialing how to here the sound of dialing for that what i have to do.

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