Modem AT commands
This page covers modem AT commands commonly used/provided by leading GSM/HF/CDMA/LTE modem manufacturers. It includes AT,AT+CFUN,ATD,ATA,ATH,AT+CGDCONT,AT+COPS,AT+CGMR,AT+CGATT and more.
AT commands are very popular to configure/monitor and put modem in various functionalities/modem. It is applicable to various modems from different technologies which include HF, GSM, CDMA, LTE and more.
AT commands vary manufacturer to manufacturer as each one design and develop their own set of commands catering to various functionalities. Basic set is derived from Hayes standard AT commands.
Following is the list of AT commands commonly used across various modem manufacturers.
| AT command | Description |
| AT | This command is used to check communication between the module and the computer. |
| AT+CMGF=<mode> AT+CMGF AT+CMGL AT+CMGR AT+CMGS AT+CMSS AT+CMGW AT+CMGD |
set the SMS mode(PDU mode or text mode). Message format List messages Read message Send message Send message from storage Write message to memory Delete message |
| AT +CFUN=value | -Set functionality to various modes such as GSM, CDMA and LTE. It is mainly used in modem providing multi-RAT support. -Value=some number 0 to 6 or more. 1 means full functionality |
| ATD <number> | used to call a phone number. |
| ATA | used to answer an incoming call |
| ATH | used to disconnect the established call |
| AT+CGDCONT=1,"IP address","APN" | AT command to define PDP context,APN is gateway between GPRS network & internet. |
| AT+COPS=1,2,26201 | Manual PLMN selection |
| AT+COPS? | Will provide PLMN information set in the modem |
| AT+CGMR | Display the version of the software loaded on the modem |
| AT+CGATT | Used to activate and deactivate GPRS or PS connection AT+CGATT=0 deactivates and AT+CGATT=1 activates the GPRS |
Useful references on AT commands
1. www.3gpp.org/ftp/Specs/html-info/27-series.htm
2. ETSI GSM 07.07 AT commands, GPRS
3. ETSI GSM 07.05 AT commands for Short Message Service (SMS) and Cell Broadcast Service (CBS)
Useful Links
GSM Tutorial
GSM mobile originated call flow
GSM Mobile Terminated Call flow
GSM protocol stack
GSM physical layer
GPRS protocol stack
GPRS tutorial