GSM Module Help - SIM900A

[Suraj143]

I want to make a call & send ASCII characters via a GSM modem.

Can this be done using SIM900A GSM modules?

I don't want to do this by sending SMS AT commands.

I want to do this by making a call & send characters not from SMS.

In simply I want to control 4 relays wirelessly using two GSM modules.

 

[Nigel Goodwin]

Most GSM modems will probably allow you to do other things (such an Internet or FTP), but using simple GSM text messages is by FAR the easiest way to do it.

Why would you want to do it any other way?.

 

[Suraj143]

Hi Nigel.

I need a speed link.SMS is too slow to deliver depending upon sms center tower delays etc......

I need to do this as old modems does.First make a call link & then send ascii while in an online link.

 

[Nigel Goodwin]

It's going to be FAR more complicated then, but your first job is to download the GSM datasheet and study it.

I would also suggest you should first connect PC's to both GSM modems, and initially write the software on the PC's (due to FAR better and faster programming, testing, and debugging). Once you have the modems doing exactly what you want, then see about porting to the processors you want to use - the PC experience could also determine what type of processor you might need?.

 

[Diver300]

This seems to show how you detect the tones:-

http://www.mt-system.ru/sites/default/files/sim900_ddet_application_note_v1.00.pdf

 

[Suraj143]

Thanks diver thats a very useful link.

By the way I hope there is AT commands for sending DTMF tones as well