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.
Usage
The AT commands can be used with GSM and GPRS MODEMs or phone to access these services and information:
- SMS
- MMS
- Fax
- 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:
- Test: The test command is utilized to check the compatibility of a command by a modem.SYNTAX: AT<command name>=?
- Read: Read command is used for extracting the mobile or modem settings required for operations.SYNTAX: AT<command name>?
- Set: This commands is used to make changes into mobile phone or modem settings required for the operation.SYNTAX: AT<command name>=value1, value2, …, valueN
- Execution: As the name suggests, this command is used to execute the said operation.
SYNTAX: AT<command name>=parameter1, parameter2, …, parameterN
Most Commonly Used AT Commands
The below 7 are the most commonly used AT commands:
- 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.
- +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.SYNTAX: AT+CMGF=<mode>
- +CMGS : Used to send SMS to a particular phone numberSYNTAX: AT+CMGS= serial number of message to be send.
- ATD : Used to make call to a particular numberSYNTAX: ATD<Phone number>;(Enter)
- 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.SYNTAX: ATA(Enter)
- +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
- ATH : this commaned is utilized to disconnect a remote user with the GSM module.SYNTAX: ATH (Enter)
List of AT Commands
| Testing : | |
| Command | Description |
| AT | Checking communication between the module and computer. |
| Call control : | |
| Command | Description |
| ATA | Answer command |
| ATD | Dial command |
| ATH | Hang up call |
| ATL | Monitor speaker loudness |
| ATM | Monitor speaker mode |
| ATO | Go on-line |
| ATP | Set pulse dial as default |
| ATT | Set tone dial as default |
| AT+CSTA | Select type of address |
| AT+CRC | Cellular result codes |
| Data card Control : | |
| Command | Description |
| ATI | Identification |
| ATS | Select an S-register |
| ATZ | Recall stored profile |
| AT&F | Restore factory settings |
| AT&V | View active configuration |
| AT&W | Store parameters in given profile |
| AT&Y | Select Set as power up option |
| AT+CLCK | Facility lock command |
| AT+COLP | Connected line identification presentation |
| AT+GCAP | Request complete capabilities list |
| AT+GMI | Request manufacturer identification |
| AT+GMM | Request model identification |
| AT+GMR | Request revision identification |
| AT+GSN | Request product serial number identification (IMEI) |
| Phone control : | |
| Command | Description |
| AT+CBC | Battery charge |
| AT+CGMI | Request manufacturer identification |
| AT+CGMM | Request model identification |
| AT+CGMR | Request revision identification |
| AT+CGSN | Request product serial number identification |
| AT+CMEE | Report mobile equipment error |
| AT+CPAS | Phone activity status |
| AT+CPBF | Find phone book entries |
| AT+CPBR | Read phone book entry |
| AT+CPBS | Select phone book memory storage |
| AT+CPBW | Write phone book entry |
| AT+CSCS | Select TE character set |
| AT+CSQ | Signal quality |
| Computer data interface : | |
| Command | Description |
| ATE | Command Echo |
| ATQ | Result code suppression |
| ATV | Define response format |
| ATX | Response range selection |
| AT&C | Define DCD usage |
| AT&D | Define DTR usage |
| AT&K | Select flow control |
| AT&Q | Define communications mode option |
| AT&S | Define DSR option |
| AT+ICF | DTE-DCE character framing |
| AT+IFC | DTE-DCE Local flow control |
| AT+IPR | Fixed DTE rate |
| Service : | |
| Command | Description |
| AT+CLIP | Calling line identification presentation |
| AT+CR | Service reporting control |
| AT+DR | Data compression reporting |
| AT+ILRR | DTE-DCE local rate reporting |
| Network Communication parameter : | |
| Command | Description |
| ATB | Communications standard option |
| AT+CBST | Select bearer service type |
| AT+CEER | Extended error report |
| AT+CRLP | Radio link protocol |
| AT+DS | Data compression |
| Miscellaneous : | |
| Command | Description |
| A/ | Re-execute command line |
| AT? | Command help |
| AT*C | Start SMS interpreter |
| AT*T | Enter SMS block mode protocol |
| AT*V | Activate V.25bis mode |
| AT*NOKIATEST | Test command |
| AT+CESP | Enter SMS block mode protocol |
| SMS Text mode : | |
| Command | Description |
| AT+CSMS | Select message service |
| AT+CPMS | Preferred message storage |
| AT+CMGF | Message format |
| AT+CSCA | Service centre address |
| AT+CSMP | Set text mode parameters |
| AT+CSDH | Show text mode parameters |
| AT+CSCB | Select cell broadcast message types |
| AT+CSAS | Save settings |
| AT+CRES | Restore settings |
| AT+CNMI | New message indications to TE |
| AT+CMGL | List messages |
| AT+CMGR | Read message |
| AT+CMGS | Send message |
| AT+CMSS | Send message from storage |
| AT+CMGW | Write message to memory |
| AT+CMGD | Delete message |
| SMS PDU mode : | |
| Command | Description |
| AT+CMGL | List Messages |
| AT+CMGR | Read message |
| AT+CMGS | Send message |
| AT+CMGW | Write message to memory |
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