Re: RS232 GSM Modem

[Dan Williams <dcbw redhat com>]

On Wed, 2010-04-28 at 09:37 +0200, toabctl wrote:
> Hi,
> 
> i want to use network-manager 0.8 in debian embedded system. I want to
> connect the system with network/modem manager to the gsm network and
> have a Siemens TC63i modem for that available.
> I can manually use the modem with the AT-Commands, but i don't know
> how to setup the connection with network/modem manager.
> Question:
> 1) How does network-manager detect that the modem is connected? Or how
> can i tell networkmanager on which port the modem is attached? I use a
> rs232<->usb adapter so the port is /dev/ttyUSB0 .

ModemManager uses udev for device detection.  It listens for udev events
(which you can also listen for with udevmonitor) and when it receives a
notification of a new serial port, it will inspect that port and attempt
to probe it.  There are a number of requirements of the port though; it
verifies that the kernel has assigned a driver name to the port or one
of the port's parents, and it attempts to grab the port's physical
device.  Given that it's USB, it *should* work.  But if it doesn't, and
you have a chance to grab the ModemManager source [1], there's a tool
called 'lsudev' in the test/ directory that can give us an idea of the
udev-provided information of the device.

> 2) How does the connection-config looks like?

ModemManager is just a tool to control the modem, it doesn't store any
configuration about it.  The configuration is provided by a program that
tells ModemManager what to do.  There are a few ways to do that;
NetworkManager provides a general modem control solution, but you can
also write your own app that uses D-Bus to tell ModemManager what to do
with the modem.  See test/mm-test.py for a short example of how to use
python and D-Bus to make MM connect the modem and get information out of
it.

Dan