Data transfer with GSM modem / module

GSM modems / GSM modules offers SMS, data calls, fax and voice calls. The AT  command set of a GSM modem inludes nearly 100 different AT commands. A few of that AT commands are equal to normal PSTN modem, so that it is possible to change a PSTN modem to a GSM modem in a lot of data applications. Please note that a GSM modem needs the PIN like your GSM handset, after power on. You have to send a PIN with the command AT+CPIN or you have to ask your GSM operator for SIM cards without PIN. Not every GSM operator offers SIM cards, where you can turn the PIN off.

List of Short Message handling commands in a GSM module

• AT+CSCA, AT+CMG, AT+CMGR, AT+CMGS, AT+CMSS, AT+CMGW, AT+CMGD, AT+CSMS

• AT+CPMS. AT+CMGF,  AT+CSMP, AT+CSDH, AT+CSCS, AT+CNMI, AT+CSCB

It depents on your application which of the commands you have to use.

Manuals and specifications

As a minimum you will need the documantation as below.

• Manual for GSM modem ( module)

• ETSI Specifications:  GSM 07.05, GSM 07.07, GSM 03.40,  GSM 03.38

Nice to have

• International  Telecommunication Union :  V25ter