Technology Blog Dietmar Zlabinger

The Drei “Internet to go” mobile broadband prepaid-package comes with an Option Icon72 USB modem. The original driver supports MS Windows, but of course, running it under Linux is much more interesting.

The Option Icon72 (GTM378) is an UMTS-modem with an USB interface. It is very similar to the popular Huawei E220 modem. The difficult part is to switch this modem from mass-storage mode (Windows driver) to the USB-serial mode. There is a tool for the old Option 3,6 MBit-box called “icon_switch” written by Josua Dietze. Unfortunately the newer Icon72 uses different initialization commands. A newer and more flexible – tool “USB_modeswitch” written by the same author includes a configuration file for the Icon72 but that configuration did not work with my Icon72 (firmware version 2.2.0Hd, Date: Apr 13 2007, Time: 12:09:19).

By sniffing the USB communication under Windows using “SniffUSB” I found a number of commands sent to the device. Sending the same sequence allowed me use the device under Linux. The result of my work was a modified version of icon_switch, I named it icon_switch72 which supports switching the Option Icon72 into modem-mode.

Download: icon_switch72.c (static binary: icon_switch72static)

For the rest (how to compile and how to configure ppp) I basically refer to the page of Alrecht Gebhard, but:

• use icon_switch72 instead of the original source file named icon_switch
• modprobe usbserial vendor=0×0af0 product=0×6901
• the modem requires a specific init sequence (again, result of sniffing – the original sequence was a bit longer)
  
• to connect to Drei use the APN “drei.at“

The whole solution is by far not as mature as the original Windows driver, in the original setup, a number of parameters are checked before the connection is set up, and also during the connection a second (and third?) serial port are used to control the quality and/or to send and receive SMS (under Linux this would require a different concept for the ppp daemon).

This entry was posted on Sunday, December 9th, 2007 at 1:03 am and is filed under Uncategorized. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.