22.4. Example Demonstrating How to Use the +CPMS AT Command to Select the Message Storage Areas to be Used

Now let's see an example that demonstrates how to use the +CPMS AT command to select the message storage areas to be used for various SMS operations.

Finding the Message Storage Areas Supported by the GSM/GPRS Modem or Mobile Phone

First, enter the command line "AT+CPMS=?" in a terminal program (for example, Windows' HyperTerminal program) to find the message storage areas supported by the GSM/GPRS modem or mobile phone. Below shows the response returned from my Nokia 6021 to Windows' HyperTerminal program after the execution of the command line "AT+CPMS=?":

AT+CPMS=?
+CPMS: ("ME","SM"),("ME","SM"),("MT")

OK

The information response above indicates Nokia 6021 supports the use of "ME" or "SM" for SMS reading, deleting, sending and writing, while it only supports the use of "MT" for storing inbound SMS messages.

Selecting Message Storage Areas

After knowing what message storage areas are selectable, we can now perform a set operation to select the message storage areas. For example, let's say you want to instruct the GSM/GPRS modem or mobile phone to use:

• the phone message storage area for SMS reading and deleting,

• the SIM message storage area for SMS writing and sending, and

• both the phone message storage area and SIM message storage area for storing inbound SMS messages.

You should assign the string values "ME", "SM" and "MT" to the +CPMS AT command. Following shows the response returned from my Nokia 6021 mobile phone to HyperTerminal:

AT+CPMS="ME","SM","MT"
+CPMS: 2,150,2,10,4,160

OK

As you can see, there are six values in the information response of the +CPMS AT command. Following is a description of them.

The First and Second Fields: 2,150

The value 2 indicates there are currently two messages stored in the ME message storage area. 150 is the maximum number of messages that can be stored in the ME message storage area.

The Third and Fourth Fields: 2,10

The value 2 indicates there are currently two messages stored in the SM message storage area. 10 is the maximum number of messages that can be stored in the SM message storage area.

The Fifth and Sixth Fields: 4,160

The value of the fifth field of the +CPMS information response, 4, indicates there are currently four messages stored in the MT message storage area. The same result can also be obtained by calculating manually like this:

Number of messages currently stored in the ME message storage area + Number of messages currently stored in the SM message storage area
= 2 + 2
= 4

The value of the sixth field of the +CPMS information response, 160, is the maximum number of messages that can be stored in the MT message storage area. The same result can also be obtained by calculating manually like this:

Maximum number of messages that can be stored in the ME message storage area + Maximum number of messages that can be stored in the SM message storage area
= 150 + 10
= 160

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