AT commands are a list of commands that you can use to communicate with any kind of a mobile phone or a GSM module serially. First you have to identify the GSM module and it’s own AT commands list first. In a case that you don’t have a GSM module, you can use a basic mobile phone connected to the pc as a gsm module. (note it’s not working stand alone, always with the PC)
After connecting the mobile/GSM module to the PC via serial or USB try to communicate with it with using a hyper terminal(win XP) or Putty client(any OS). Download putty from here.
http://www.youtube.com/watch?v=Nvf_QBez8w0
Same way find the serial port of the GSM module and try to communicate.
There are various at commands to select sms mode, dial a number, Bluetooth(mobiles with bluetooth), access sim memory and all operations.
Ex: ATD 0711234567;
//dials the number
ATH
Hang the phone
Note : if you are using a mobile phone, there’s a big possibility of it’s not supporting the text mode but the PDU mode. To check the format it supports, type AT+CMGF=? in the terminal. If the device returns “0” it supports only the pdu mode. That implies you can’t send a text as it’s but need to convert into PDU format.
If it returns 1 or 0,1 it says it supports text mode and both respectively.
Interfacing with the IC
After you are done with your mobile/gsm module and understand the AT commands, use ISIS to simulate the circuit.
AT commands can be issued to the device via HSEROUT/TX pin of the IC. And will be received by the RX pin of the device. (Module or the phone. If it’s a micro usb phone, u don’t need to worry about the TX,RX of the device)
To output a command to the device using hardware serial port of the PIC,
hserout [“ATD 711234567;”,13,10];
//13 : carriage return , 10: new line character
