23.4. Example
Demonstrating How to Use the +CMGW AT Command to Write SMS Text
Messages to Message Storage in SMS Text Mode
Now
let's see a more detailed example that demonstrates how to use the
+CMGW AT command to write SMS text messages to message storage in SMS
text mode and how the +CMGW AT command should be used together with
other AT commands.
Instructing
the GSM/GPRS Modem or Mobile Phone to Operate in SMS Text Mode
First,
enter the command line "AT+CMGF=1" in a terminal program
(for example, HyperTerminal in Microsoft Windows) to instruct the
GSM/GPRS modem or mobile phone to operate in SMS text mode. This step
is necessary because the default mode is SMS PDU mode. Below shows
the response returned from Nokia 6021 to HyperTerminal after the
execution of the command line "AT+CMGF=1":
AT+CMGF=1
OK
The
final result code OK indicates the +CMGF AT command was executed
successfully. If the final result code ERROR is returned, it is
likely that the GSM/GPRS modem or mobile phone does not support SMS
text mode. To check whether the GSM/GPRS modem or mobile phone
supports SMS text mode, enter the command line "AT+CMGF=?"
in the terminal program. Here is the response returned from Nokia
6021 to HyperTerminal:
AT+CMGF=?
+CMGF:
(0,1)
OK
The
values in the parentheses indicate the modes that the GSM/GPRS modem
or mobile phone can operate in. The value 0 represents SMS PDU mode
and the value 1 represents SMS text mode. From the above response, we
know that Nokia 6021 can operate in either SMS PDU mode or SMS text
mode. See the section titled "Selecting
the Operating Mode (AT+CMGF)" of this SMS tutorial if you
want to learn further details about the +CMGF AT command.
Selecting
the Message Storage Area to Write SMS Text Messages to
Second,
use the AT command +CPMS (command name in text: Preferred Message
Storage) to select the message storage area to write SMS text
messages to. For example, to instruct the GSM/GPRS modem or mobile
phone to use the message storage area in the SIM card for the AT
command +CMGW, assign the string value "SM" to the second
parameter of the +CPMS AT command, like this:
AT+CPMS="ME","SM"
The
first parameter of the +CPMS AT command is used to select the message
storage area for reading and deleting SMS messages. It has no use to
us here. So, it does not matter what value is assigned to the first
parameter.
Now
press the Enter key on the keyboard and you should see something
similar to this:
AT+CPMS="ME","SM"
+CPMS:
2,150,2,10,4,160
OK
Detailed
information about the +CPMS AT command is available in the earlier
section "Preferred Message
Storage (AT+CPMS)" of this SMS tutorial.
Setting
the SMSC Number to be Stored with the SMS Text Message
Third,
use the AT command +CSCA (command name in text: Service Centre
Address) to set the SMSC number to be stored with the SMS text
message. Later if you send the SMS text message, it will be
transmitted via the SMSC at this number. Usually the default setting
is correct and you do not need to make any changes. Below
demonstrates how to use the +CSCA AT command to set "+85290000000"
as the SMSC number:
AT+CSCA="+85290000000"
OK
Detailed
information about the +CSCA AT command can be found in the "Setting
or Reading the Service Center Address / SMSC Address (AT+CSCA)"
section of this SMS tutorial.
Writing
Text Messages
Fourth,
you can now use the +CMGW AT command to write a text message to the
message storage area. Suppose you want the destination mobile phone
number to be +85291234567 and the message status to be "stored
unsent", you should enter something like this in the terminal
program:
AT+CMGW="+85291234567",145,"STO
UNSENT"
Then,
press the Enter key of the keyboard to send a carriage return
character to the GSM/GPRS modem or mobile phone. The GSM/GPRS modem
or mobile phone will send back a prompt
formed by four characters. They are the carriage return character,
the linefeed character, the ">" character and the space
character. If all characters are to be displayed, the
characters you have sent to and received from the GSM/GPRS modem or
mobile phone so far are:
AT+CMGW="+85291234567",145,"STO
UNSENT"<CR>
<CR><LF>><Space>
However,
the carriage return character and linefeed character have special
meanings to a terminal program. When a terminal program sees a
carriage return character, it moves the cursor to the beginning of
the current line. When it sees a linefeed character, it moves the
cursor to the same position on the next line. So, here is what you
will actually see in a terminal program such as HyperTerminal:
AT+CMGW="+85291234567",145,"STO
UNSENT"
>
If
you want to cancel the write command at this point, press the Esc key
on the keyboard. The GSM/GPRS modem or mobile phone will then return
the OK final result code. Here shows the response returned from Nokia
6021:
AT+CMGW="+85291234567",145,"STO
UNSENT"
>
OK
Some
mobile devices return a slightly different response. One example is
Philips 598:
AT+CMGW="+85291234567",145,"STO
UNSENT"
>
OK
If
you do not want to cancel the write command, enter the body of the
SMS text message that you want to write to the message storage area.
Press Enter on the keyboard if you want to start a new line. When
finished, press Ctrl+z on the keyboard. The GSM/GPRS modem or mobile
phone then attempts to write the text message to the message storage
area and returns a response to the computer / PC. Suppose the SMS
text message is "It is easy to write text messages.". Below
shows what you should see in a terminal program:
AT+CMGW="+85291234567",145,"STO
UNSENT"
> It is easy to write text messages.
+CMGW:
3
OK
The
value in the information response is the index that indicates the
location where the SMS text message is stored in the message storage
area. In the above example, the information response tells us that
the SMS text message "It is easy to write text messages."
has been written to the memory location at index 3.
The
final result code OK tells us the execution of the +CMGW AT command
is successful. If it fails, the GSM/GPRS modem or mobile phone will
return either the final result code ERROR or +CMS ERROR. For example,
if the message storage area is out of storage space, the GSM/GPRS
modem or mobile phone will return +CMS error 322, like this:
AT+CMGW="+85291234567",145,"STO
UNSENT"
> It is easy to write text messages.
+CMS
ERROR: 322
|
Feedback Form (ExpandCollapse)
|
|
