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modem-at-commands.md

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Sending AT commands to GSM USB modem

Chan dongle software enables users to send so called AT commands to your GSM stick. AT stands for Attention and these commands are used for controlling GSM modems.

You can send AT commands to any GSM modem (GSM USB stick) with commands:

sudo su
asterisk -rvvv
dongle cmd <device> <AT_command>

For instance, sending command to device dongle0:

sudo su
asterisk -rvvv
dongle cmd dongle0 ATI

This AT command will get relevant information from modem.

Some useful AT commands you can use:

AT command                    Description
AT+CCWA=0,0,1                 disable call-waiting
AT+CFUN=1,1                   reboot modem
AT^CARDLOCK="<code>"          send unlock code
AT^SYSCFG=13,0,3FFFFFFF,0,3   modem 2G only, automatic search any band, no roaming
AT^SYSCFG=2,0,3FFFFFFF,2,4    Any
AT^SYSCFG=13,1,3FFFFFFF,2,4   2G only
AT^SYSCFG=14,2,3FFFFFFF,2,4   3G only
AT^SYSCFG=2,1,3FFFFFFF,2,4    2G preferred
AT^SYSCFG=2,2,3FFFFFFF,2,4    3G preferred
AT^U2DIAG=0                   enable modem function only
ATI                           get relevant information from modem
ATZ                           reset modem configuration
AT+CIMI                       read IMSI
AT+CLCK="SC",0,"<pin>"        disable PIN verification

Using 2G network only

In some cases USB dongles are not working properly. You can find out that they are using connectivity. If you will issue a command dongle show device state dongle0 in that case, GSM Registration Status will be Not registered or something similar.

The problem is, that GSM modem is sometimes "flipping" between 2G and 3G network. Solution is, that you instruct the modem to stay on 2G network only. You can do this by typing these commands:

sudo su
asterisk -rvvv
dongle cmd dongle0 AT^SYSCFG=13,1,3FFFFFFF,2,4

But because you want this to be set automatically when the system boots up, just add this line into your root crontab (sudo crontab -e):

@reboot /usr/sbin/asterisk -rx 'dongle cmd dongle0 AT^SYSCFG=13,1,3FFFFFFF,2,4'

After reboot, your USB GSM modem will be automatically instructed to use 2G network only.

Some other dongle commands

There are several useful commands you can send to your dongle through terminal.

For instance, you can see the dongle status:

sudo su
/usr/sbin/asterisk -rx 'dongle show device state dongle0'

Or dongle statistics:

sudo su
/usr/sbin/asterisk -rx 'dongle show device statistics dongle0

If you want to stop GSM dongle completely from the terminal, you can enter this command:

sudo su
/usr/sbin/asterisk -rx 'dongle stop gracefully dongle0'

Another way to stop GSM dongle (quickly):

sudo su
/usr/sbin/asterisk -rx 'dongle stop now dongle0'

You can start dongle with command:

sudo su
/usr/sbin/asterisk -rx 'dongle start dongle0'

And then you can check it's status:

sudo su
/usr/sbin/asterisk -rx 'dongle show device state dongle0'