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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.
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  

RF and Wireless Terminologies

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