Differences among different GSM modems

Archived from groups: alt.cellular.gsm (More info?)

A. Thirupathi Reddy wrote:

> Hello All,
> I am curious to know what kind of differences exists among
> different GSM modems. If some OEM says his GSM modem confirms
> to GSM standards, that should mean that it interprets all the
> GSM standard AT commands. But that is not the case, as some
> existing GSM modems do not implement all the GSM AT commands.
> So if i am writing a generic GSM modem driver that works
> with all kinds of GSM modems, what aspects should i keep in
> mind? I have noticied the following differences till now. If
> some body could add more points to this list, it will be of
> great help in developing my driver fast.
> - different initialization commands
> - physical connection (USB, RS 232, IRDA etc.)
> - more

You need to keep in mind that implementation of many AT commands
is entirely optional for modems compliant with GSM 07.07 and
07.05.

The major mechanism for accommodating this is detailed in
section 4 of GSM 07.07. Most AT commands have 3 syntactic
variants, with the "test command" form used to "test the
existence of the command and to give information about the type
of its subparameters".

John