AT commands are used to control MODEMs. AT is the abbreviation for Attention. These commands come from Hayes commands that were used by the Hayes smart modems. The Hayes commands started with AT to indicate the attention from the MODEM. The dial-up and wireless MODEMs (devices that involve machine-to-machine communication) need AT commands to interact with a computer. These include the Hayes command set as a subset, along with other extended AT commands.
AT commands with a GSM/GPRS MODEM or mobile phone can be used to access the following information and services:
1. Information and configuration pertaining to mobile device or MODEM and SIM card.
2. SMS services.
3. MMS services.
4. Fax services.
5. Data and Voice link over the mobile network.
The Hayes subset commands are called the basic commands and the commands specific to a GSM network are called extended AT commands.
What can AT commands be used for?
AT commands enable you to control everything around the modem, device, and SIM:
- Wake the device or put it in sleep mode
- Configuration of power-saving modes
- Scan for and register to available networks and radio types
- Get updates about network condition changes
- Read/send SMS and USSD
- Send data (TCP/IP)
- Get hardware and SIM information (IMEI, IMSI, etc.)
- and much more
To get started, we will talk about the syntax or the types of AT commands that can be sent to the modem.
List of AT commands:
The AT commands for both, the GSM module and the mobile phone, are listed below. Some of these commands may not be supported by all the GSM modules available. Also, there might be some commands which won’t be supported by some mobile handsets.
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 online |
| 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 a 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 center 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 a 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 a message to memory |