19.1. Using the AT
Command +CSMS to Check if Mobile-originated SMS Messages and
Mobile-terminated SMS Messages are Supported
One
use of the AT command +CSMS (command name in text: Select Message
Service) is to check the message types supported by the GSM/GPRS
modem or mobile phone. There are three message types:
mobile-originated SMS messages, mobile-terminated SMS messages and
cell broadcast messages.
Mobile-originated
SMS messages refer to SMS messages that are sent from a mobile device
to an SMSC, i.e. outbound SMS messages.
Mobile-terminated
SMS messages refer to SMS messages that are sent from an SMSC to a
mobile device, i.e. inbound SMS messages.
Cell
broadcast messages are text messages pushed to subscribers located in
a certain mobile network area by the network operator. These text
messages may contain news, weather information, etc.
Here
is an example that demonstrates how to use the +CSMS AT command to
check if mobile-originated and mobile-terminated SMS messages are
supported. First, send the read command "+CSMS?" to the
GSM/GPRS modem or mobile phone. The response returned from our Nokia
6021 to HyperTerminal is shown below:
AT+CSMS? +CSMS:
0,1,1,1
OK
As
you can see, the information response contains four values. The
second, third and fourth values indicate whether Nokia 6021 supports
mobile-terminated SMS messages, mobile-originated SMS messages and
cell broadcast messages respectively. If the value is 1, it means the
message type is supported. If the value is 0, it means the message
type is not supported.
For
Nokia 6021:
The
third value in the information response is 1, which indicates Nokia
6021 supports mobile-originated SMS messages. So, Nokia 6021 is
capable of sending SMS messages to an SMSC.
The
second value in the information response is 1, which indicates Nokia
6021 supports mobile-terminated SMS messages. So, Nokia 6021 is
capable of receiving SMS messages from an SMSC.
If
the final result code "ERROR" is returned (as shown below),
it is likely that the +CSMS AT command is not supported by the mobile
device.
AT+CSMS? ERROR
To
confirm, send the test command "+CSMS=?" to the GSM/GPRS
modem or mobile phone. If the final result code "ERROR" is
returned (as shown below), it means the mobile device does not
support the +CSMS AT command.
AT+CSMS=? ERROR
Note
that +CSMS is a mandatory command in the AT command set for SMS
messaging. If it is not supported, normally the whole AT command set
for SMS messaging is not supported.
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