Using a Cellular Modem and SIM Card on TechNexion Products

Introduction

This guide lines out how to scan and connect to a 3G phone network using TechNexion products with a SIM card slot.

Getting Started

To follow this guide a SIM-card and a (PCIe) 3G modem is needed.

Plug in the SIM card in the SIM card slot, and the modem in the corresponding PCIe / M2 slot.

Compile a driver for your modem and boot up your system.

Scanning for Networks

The communication with the SIM card will be performed by the modem, and controlled with old-fashioned AT-commands.

First enable the modem driver if not built-in, example driver loading could be:

    # modprobe usb_wwan

or

    # modprobe option

but the exact modules to load depend on the modem used.

After the modem is initialized, a USB serialk interface should appear as something like /dev/ttyUSB0 or /dev/ttyACM0.

Use a terminal emulator client for interactive communication with the modem, i.e.

    # minicom -D /dev/ttyUSB0

In the terminal emulator, some usefule commands are:

• ATI -- list device information
• AT+COPS=? -- scan and list available phone networks
• AT+COPS=0,2,short_name -- connects to network by its short name
• AT^SYSINFO -- connection status

The connection status string is of the format

    ^SYSINFO:2,3,0,5,1,,4

, where:

• the first number after the colon indicate the connection status; 0 = No connection, 2 = OK
• the second is connection type; 0 = No connection, 1 = data, 2 = phone, 3 = both
• the third number is roaming state; 0 = No roaming, 1 = roaming on
• the fourth is service mode; 0 = No, 3 = GSM, 5 = WCDMA
• the fifth number is SIM status; 0 = NG, 1 = OK, 2-4 = partially OK, 255 = No SIM card detected

Example session

    ATI
    ---------
    OK
    ---------
    AT+CFUN=1
    ---------
    OK
    ---------
    AT+CPIN="0000"

Some of the commands below requires to wait 2~3 mins to get response

    AT+COPS=?
    --------------------------------------------------------------------
    +COPS: (2,"Chunghwa Telecom","Chunghwa","46692",2),(1,"TW Mobile","TWM","46697",2),(1,"Far EasTone","FET","46601",2),,(0,1,2,3,4),(0,1,2)
    ---------------------------------------------------------------------

    AT+COPS=0,2, Chunghwa
    ---------------------
    OK
    ---------------------

    AT^SYSINFO
    -------------------------------------------------
    ^SYSINFO:2,3,0,5,1,,4
    -------------------------------------------------