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gsmat-commandmodem

about types of AT-COMMAND

While I was reading about AT-COMMANDS and their functions, I realized that there are types of them according to the character that came after AT.

Like +, %, $, #, *, &, \ or a letter.

1.What do each of these characters refer to? "I need details"

I'm interested in commands that have #, but my modem doesn't get me any of them when I entered AT+CLAC.

2.Can I activate those command by another `AT-COMMAND` or not?

NOTE:

I'm working on a phone modem.

Solution

  • The following is good to keep in mind. GSM modems have a number of standards that they "adhere" too. Basically the standards build ontop of each other in the following manner:

    1. Serial Asynchronous Automatic Dialling and Control (V.25ter)
    2. AT command set for GSM Mobile Equipment (GSM 07.07)
    3. AT Command extended command syntax (manufacturer specific - you will need a manual from them)

    Two very important facts to help you out when you don't want to read through too many documents are:

    1. You can verify if a AT Command is supported by using the =? syntax. Normally when a command is supported by a modem then you will get a response with acceptable command values and an OK. Otherwise you will get an ERROR response back when it is not supported.
    2. Some (not all) modems support the AT+CLAC command which outputs all supported AT commands.

    So going back to the original question 1 :)

    "+" are usually standard GSM AT Commands which you will find in the GSM 07.07 specification or the V.25ter specification.

    "&" are usually low level serial configuration AT commands based upon V.25ter.

    "%" tend to be manufacturer specific AT commands. So best bet here is to check your modem manufacturers AT Command Set documentation if it exists.

    "$" tend to be manufacturer specific AT commands. So best bet here is to check your modem manufacturers AT Command Set documentation if it exists.

    "#" tend to be manufacturer specific AT commands. So best bet here is to check your modem manufacturers AT Command Set documentation if it exists.

    "*" tend to be manufacturer specific AT commands. So best bet here is to check your modem manufacturers AT Command Set documentation if it exists.

    Moving onto your second question...

    Unfortunately you cannot "activate" commands. They are built into the firmware of your modem. And as you see above there are manufacturer specific AT commands that are not implemented on every GSM modem out there.

    There is one thing that you can double check and that is if you are really connected to your AT Command interface. There are usually a number of interfaces for example for GPS, manufacturer propriatory, and PPP interfaces. With the latter (PPP interfaces) you can infect execute AT commands but the command set is extremely restricted. This you can verify by executing an ATI command. I know for example with Sierra Wireless modems PPP interfaces are identified as APP1, APP2, and APP3. But this is again modem manufacturer specific.