Trouble with GSM / GPRS Modem

I've been trying to use the following modem from my arduino to send sms but have been unsuccessful.

So after several attempts i'm here. When I try AT commands from the Hyperterminal it works fine however the same commands from the arduino do not bring any reaction(no sms sent!)

The only thing that occurred to me was that this modem has a serial interface with a max232 and perhaps this was causing some unwanted conversions between the modem and the arduino. So i tried plugging out the max232 and plugging the rx/tx from the arduino into pin9/pin10 Slots of the Max232 IC base. This did not work and then i tried swaping them. It didnt work. Now I'm very much sure all of this has to do something with the way arduino talks to the gsm modem but i'm unable to figure out what it is. I would appreciate if someone can take a look at the datasheet of the modem and give me an idea. I cant figure much from the datasheet.

Pracas :-/

plugging the rx/tx from the arduino into pin9/pin10 Slots of the Max232 IC base

Just to make sure, did you connect arduino GND to the appropriate GND pin on the IC socket too? The module and the arduino need to have a common ground to be able to communicate.

Bingo! i didn't do that.... something i always seem to forget. Thanks a ton! lemme try and let you know!

It works now! Thanks once again

No worries - I'll just assume that the cheque is in the mail.

BTW how much did you pay for the module? That site is terrible to navigate - I can't find a price.

about 60$... in INR


I'm interfacing an Arduino with the libelium GPRS/GSM module that has the Hilo Sagem modem and Im having trouble sending SMS by the arduino. Im able to send SMSs in the terminal with AT commands but when I follow the tutorial that they provide the SMS is never sent. After I upgraded to firmware v7 it was able to send an SMS once but thats it. Any idea what could be the problem?

Tutorial I followed to upgrade firmware:

Tutorial for the Module and Sending SMS

Any suggestions will be appreciated.