Attention Commands or, more commonly referred to as, AT commands are the method in which one communicates to modems. The following guide runs down some of the more common commands used when interfacing with a modem and establishing a connection to the cellular network.
To begin, use your favorite terminal program (Teraterm, Putty, GTKTerm, etc.), to establish a serial connection to your Modem. Confirm that you are connected to the modem by sending over
AT the modem should respond with OK. For more on this check out this guide for Sending AT Commands to a Nova, which applies to all devices that you can communicate with via serial.
Before we dive into some of these commands, we need to go over the three operators you will find while using AT Commands.
- Question Mark ? - A question mark is the read operator which queries the current state of the command. So, for example, for the functionality command,
AT+CFUN?, the question mark reads the state of the command and lets you know what functionality the modem is on.
- Equals Sign = - An equals sign is the set operator and, as the name suggests, sets the command on the right of the symbol to the value on the left of the symbol.
AT+CFUN=1changes the functionality to mode 1.
- Equals Sign and Question Mark =? - An equals sign followed by a question mark is the test operator which shows you the different options you have to set that command to. Using it on
AT+CFUNwill show you all the different functionality modes the modem has. Using =? on the network registration command,
AT+COPS, shows you which networks are in reach of the modem.
The list below is a compilation of the most commonly used commands for debugging.