thanx a lot.

On 10/30/06, Alexandre Pereira Nunes <> wrote:
Rajagopalan Parthasarathy escreveu:

> hi
> thanx a lot for the info. The GSM module(MC75) is class B(GPRS). So
> does it mean that i have to implement the pin Ring0 using some other
> pin(GPIO, as dave said) in software(in the driver)??

As far as I know, only if you need to be able to get incoming call info
while connected to gprs/csd.  I've developed quite a few solutions in
gsm world, with class b modems, inclusive, without needing this
functionality at all. But there are indeed some scenarios where you
can't avoid that. It depends on what you're planning to do. For the
basics all you'll ever need is tx, rx and ground.

If I were to do it, I would just poll a regular GPIO in software and
take actions from there. It's the easy way to go. You don't need
performance or have latency issues (disconnecting the modem for
answering the call takes quite a long time anyway) on this case, so you
can just use /proc/gpio as described on the wiki.

> Also can you give pointers to sites that have general info on GSM
> modules/modems?

All I ever used was the documentation provided by the modems. At least
the motorola series has public documents, but for the siemens I had to
sign a  NDA (and I only got docs for some models), so I can't point you
to these (you probably already have them anyway).

The thing is that altough there are GSM standards, and lots of tutorials
on doing things like sending/receiving SMS that are useful for almost
all brands of GSM phones/modems, there are other things such as GPRS
connection setting/stablishing that most companies prefer to do the hard
way (by not following the standards and doing it using a proprietary
syntax; But even when they go the other way, there are both newer and
outdated [incompatible] standards, some go one way, some go the other,
and the rest do it proprietarly. So much for standards).

In other words, you generally gain by going straight to the source (the
manufacturer's documents) rather than trying to adapt a tutorial based
on something else to work with a specific brand. Also, it's not uncommon
for modems series from the same manufacturer to be incompatible with
each other.

Good luck,


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