All You Wanted To Know About AT And GSM AT Commands

Read on to know what AT commands are and what do they do.



What are AT commands?

AT commands are commands which are used to control the modems where AT stands for Attention. These commands were derived from Hayes commands which were used by the Hayes smart modems. Every wireless as well as the dial up modems require an AT command to interact with a computer machine. These AT commands along with other extended commands also require Hayes command set as a subset.


The AT commands can be used with GSM module and GPRS MODEMs or phone to access these services and information:




Voice link and other data over mobile network

Information and configuration concerning the mobile devices or MODEM and SIM card.

Types of AT Command

There are 4 basic types of AT commands:

  1. Test: The test command is utilised to check the compatibility of a command by a modem.


2. Read: Read command is used for extracting the mobile or modem settings required for operations.


3. Set: This commands is used to make changes into mobile phone or modem settings required for the operation.

SYNTAX: AT=value1, value2, …, valueN

4. Execution: As the name suggests, this command is used to execute the said operation.

SYNTAX: AT=parameter1, parameter2, …, parameterN

Most Commonly Used AT Commands

The below 7 are the most commonly used AT commands:

  1. AT : Used to check the interaction between the computer and the module. This command is usually replied with an OK if the port and the module can connect correctly, else wise it comes back with a result code ERROR.

2. +CMGF : Used to setup the SMS mode. By adding 1 or 0 with the command text or PDU mode can be selected. Here the text mode is easy to operate although it only allows a few limited features of SMS. Where as the PDU mode allows a more detailed access to the SMS service, although to use this you require some basic knowledge of TDPU.


3. +CMGS : Used to send SMS to a particular phone number

SYNTAX: AT+CMGS= serial number of message to be send.

4. ATD : Used to make call to a particular number


5. ATA : Used to answer the incoming calls. The calls are denoted by a message ‘RING’ which duplicated for every ring of the call. After the call ends a message saying ‘NO CARRIER’ is displayed.


6. +CMGW: Used to store a message in the SIM. After the execution of the command, the ‘>’ sign appears in the next line where the message can be entered.

SYNTAX: AT+CMGW=” Phone number”> Message to be stored Ctrl+z

7. ATH : this commaned is utilized to disconnect a remote user with the GSM module.


List of AT Commands

Testing :
ATChecking communication between the module and computer.
Call control :
ATAAnswer command
ATDDial command
ATHHang up call
ATLMonitor speaker loudness
ATMMonitor speaker mode
ATOGo on-line
ATPSet pulse dial as default
ATTSet tone dial as default
AT+CSTASelect type of address
AT+CRCCellular result codes
Data card Control :
ATSSelect an S-register
ATZRecall stored profile
AT&FRestore factory settings
AT&VView active configuration
AT&WStore parameters in given profile
AT&YSelect Set as power up option
AT+CLCKFacility lock command
AT+COLPConnected line identification presentation
AT+GCAPRequest complete capabilities list
AT+GMIRequest manufacturer identification
AT+GMMRequest model identification
AT+GMRRequest revision identification
AT+GSNRequest product serial number identification (IMEI)
Phone control :
AT+CBCBattery charge
AT+CGMIRequest manufacturer identification
AT+CGMMRequest model identification
AT+CGMRRequest revision identification
AT+CGSNRequest product serial number identification
AT+CMEEReport mobile equipment error
AT+CPASPhone activity status
AT+CPBFFind phone book entries
AT+CPBRRead phone book entry
AT+CPBSSelect phone book memory storage
AT+CPBWWrite phone book entry
AT+CSCSSelect TE character set
AT+CSQSignal quality
Computer data interface :
ATECommand Echo
ATQResult code suppression
ATVDefine response format
ATXResponse range selection
AT&CDefine DCD usage
AT&DDefine DTR usage
AT&KSelect flow control
AT&QDefine communications mode option
AT&SDefine DSR option
AT+ICFDTE-DCE character framing
AT+IFCDTE-DCE Local flow control
AT+IPRFixed DTE rate
Service :
AT+CLIPCalling line identification presentation
AT+CRService reporting control
AT+DRData compression reporting
AT+ILRRDTE-DCE local rate reporting
Network Communication parameter :
ATBCommunications standard option
AT+CBSTSelect bearer service type
AT+CEERExtended error report
AT+CRLPRadio link protocol
AT+DSData compression
Miscellaneous :
A/Re-execute command line
AT?Command help
AT*CStart SMS interpreter
AT*TEnter SMS block mode protocol
AT*VActivate V.25bis mode
AT*NOKIATESTTest command
AT+CESPEnter SMS block mode protocol
SMS Text mode :
AT+CSMSSelect message service
AT+CPMSPreferred message storage
AT+CMGFMessage format
AT+CSCAService centre address
AT+CSMPSet text mode parameters
AT+CSDHShow text mode parameters
AT+CSCBSelect cell broadcast message types
AT+CSASSave settings
AT+CRESRestore settings
AT+CNMINew message indications to TE
AT+CMGLList messages
AT+CMGRRead message
AT+CMGSSend message
AT+CMSSSend message from storage
AT+CMGWWrite message to memory
AT+CMGDDelete message
SMS PDU mode :
AT+CMGLList Messages
AT+CMGRRead message
AT+CMGSSend message
AT+CMGWWrite message to memory


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