Hello,

I have to make several dataloggers with gsm modules. I want to transmit data and alarms to common computer which archieves all the data.

At first my plan was to exchange data by two-way DTMF. Our mobile operator does not charge calls less than 4 seconds long. Since there is only 20 bytes in a package I guess I would manage to do in 4 sec window, using DTMF, so data exchange would be free. But in case our mobile operator policy changes there would be high data transmition costs. (about 10cents/data package). So I think of GPRS data exchange.

Is there a simple way to exchange data between two gsm phones/modules over GPRS? I have looked some scripts to send email etc. and they looked relatively simple. But what in case raw data exchange? Has anybody done it? Which (!low cost!) GSM module do you recommend?

I searched for similar, but didn't find anything similar. Everybody wants to use tcp/ip.

thank you for your help

regards, Damjan