AT commands' syntax
Case Sensitivity -
The AT commands are generally used in uppercase letters. However some MODEMs and mobile phones allow both uppercase and small case letters.
Single Command -
The AT commands include a prefix AT which indicates the beginning of the command to MODEM; and a carriage return which indicates the end of the command.
However string ‘AT’ itself is not the part of the command. For example in ATD, D is the command name not ATD.
The extended AT commands have a ‘+’ in the command name.
For example: AT+CGMI<Carriage return>
Command Line -
Multiple AT commands can be sent to MODEM in a single command line. The commands in a line are separated by a semi-colon (;).
For example: AT+CGMI; +CBS<Carriage return>
String in Command Line -
Strings in a command line are enclosed in double quotes.
For example: AT+CGML=”ALL”<Carriage return>