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Accessing the CR48's SIM slot

Here's what has been found:
The Gobi 2000 does support AT&T, and it's unlocked. To switch carriers, you need to swap firmwares. Google was nice enough to provide most of the common carrier firmwares.

  • The various firmwares live in /opt/Qualcomm/Images2k/Novatel
  • Google includes firmware for these carriers:
  • 1 ("Verizon Wireless")
  • 2 ("AT&T")
  • 3 ("Sprint")
  • 6 ("UMTS")
  • 14 (???)
  • generic UMTS (not sure why it's different from 6.)

For reference, see

Google made it easy to switch firmwares.
Here are the relevant tools at your disposal:

  • /usr/bin/modem - Google's user-friendly Cr48 modem management tool (shell script)
  • /usr/bin/modem status your new best friend
  • /usr/bin/modem factory-reset /org/chromium/ModemManager/Gobi/# spc 000000 factory reset; replace # with number from modem status
  • /usr/bin/modem activate-manual ... CDMA manual activation only
  • /usr/bin/modem_set_carrier - Google's undocumented firmware swapping tool (shell script)
  • /usr/bin/dbus-send - Direct access to D-Bus, allowing you to send custom commands
  • /usr/bin/mm-cromo-wrapper - Google's user-friendly wrapper for dbus-send
  • /usr/bin/dbusxx-introspect - Navigate an object's D-Bus interface for methods, properties, and signals
  • /opt/Qualcomm/bin/gobi-factory-reset spc 000000 - Resets your modem to its default settings. Does not clear activation data.
  • /usr/lib/ - Google's shell script library for interfacing with the modem. No UI, but worth looking at.
  • /usr/share/mobile-broadband-provider-info/serviceproviders.xml - The list of all service providers supported by Chromium OS, with their APN info. AT&T's is listed and correct (unless you're on the iPhone data plan).

So, how far did I get? So close.

  • modem status to get the path for the modem. replace # below.
  • modem factory-reset /org/chromium/ModemManager/Gobi/# 000000
  • modem_set_carrier "AT&T"
  • modem status

At this point, I see lots of good things. My AT&T SIM's cell phone number is listed as my MDN. The modem is set up to use UMTS, and claims to have signal.

The problem is activation. It looks like we need to use org.freedesktop.ModemManager.Modem.Simple.Connect. The problem is, this command takes a mixed array ({string,variant}) -- which can't be created using any of the provided command line tools.
In the method documentation for "ActivateManualDebug" in Google's spec "mm-modem-cdma.xml", they make note of this bug. ("Workaround for the fact that dbus-send cannot send dictionaries of variants. Calls ActivateManual, with system_id converted to int.")

So, given the limited information I have, it looks like we can't activate an UMTS connection without writing our own (C++/Python) D-Bus interface to facilitate activation. I'm a newb with all of this D-Bus nonsense, so take my conclusion with a grain of salt. But this is where I gave up.

Relevant docs:

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