After testing the communication between the PC and GSM/GPRS modem/mobile phone, the next thing that you may want to do is to check if the GSM/GPRS modem or mobile phone supports the use of AT commands to send, receive and read SMS messages. Most GSM/GPRS modems support all three functions. However, only some mobile phones support all of them.
Sending SMS Messages
To find out whether a GSM/GPRS modem or mobile phone supports the sending of SMS messages through AT commands, you have to:
Use the AT command +CSMS (command name in text: Select Message Service) to check whether mobile-originated SMS messages are supported.
Perform test operations to check whether +CMGS (command name in text: Send Message) and/or +CMSS (command name in text: Send Message from Storage) are supported.
(You may want to check the AT commands +CMGW [command name in text: Write Message to Memory] and +CMGD [command name in text: Delete Message] in addition as they are sometimes used together with +CMSS.)
Receiving SMS Messages and Reading SMS Messages from Message Storage
To find out whether a GSM/GPRS modem or mobile phone supports the receiving and reading of SMS messages through AT commands, you have to:
Use the AT command +CSMS (command name in text: Select Message Service) to check whether mobile-terminated SMS messages are supported.
Perform test operations to check whether +CNMI (command name in text: New Message Indications to TE), +CMGL (command name in text: List Messages) and/or +CMGR (command name in text: Read Message) are supported.
If the GSM/GPRS modem or mobile phone supports the +CNMI AT command, it can send a notification or directly forward the message to the PC whenever a new SMS message arrives.
If the GSM/GPRS modem or mobile phone does not support +CNMI but supports +CMGL and/or +CMGR, the PC has to poll the GSM/GPRS modem or mobile phone repeatedly in order to know if any new SMS messages have arrived.
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.
Checking if the AT Commands Required for Sending, Receiving and Reading SMS Messages are Supported
The next thing to do is to check if the AT commands required for sending, receiving and reading SMS messages are supported by the mobile phone or GSM/GPRS modem. As pointed out earlier in this SMS tutorial, you can check if a certain AT command is supported by performing a test operation. Simply execute an AT command with "=?" attached at its end. For example, "AT+CMGS=?".
Before we begin the check, let's go through an overview of the AT commands that are required for sending, receiving and reading SMS messages. You will learn which AT commands should be checked and get a general idea about when these AT commands should be used.
1. Overview of the AT Commands Required
For Sending SMS Messages
To send SMS messages via AT commands, the GSM/GPRS modem or mobile phone has to support either +CMGS (command name in text: Send Message) or +CMSS (command name in text: Send Message from Storage). You may also find +CMGW (command name in text: Write Message to Memory) and +CMGD (command name in text: Delete Message) useful, since they are sometimes used together with +CMSS. +CMSS is used to send an SMS message located in the message storage area. If an SMS message does not exist in the message storage area, you must first use the AT command +CMGW to write the SMS message to the message storage area before you can use the AT command +CMSS to send the SMS message to the SMSC. After message submission, you may use the AT command +CMGD to delete the SMS message to free some space from the message storage area.
For Receiving and Reading SMS Messages
To receive and read SMS messages via AT commands, the GSM/GPRS modem or mobile phone has to support the AT command +CNMI (command name in text: New Message Indications to TE. TE stands for Terminal Equipment, which is the equipment that controls the GSM/GPRS modem or mobile phone. For example, a PC / computer), +CMGL (command name in text: List Messages), or +CMGR (command name in text: Read Messages).
The AT command +CNMI is used to specify how newly arrived SMS messages should be handled. You can tell the GSM/GPRS modem or mobile phone either to forward newly arrived SMS messages directly to the PC, or to save them in message storage and then notify the PC about their locations in message storage.
The AT command +CMGL is used to read all SMS messages that have a certain status (e.g. "received unread", "received read", etc) from the message storage area, while the AT command +CMGR is used to read the SMS message saved at a certain location of the message storage area.
2. Beginning the Check
Now that you've learned the AT commands required for outbound and inbound SMS messaging are +CMGS, +CMSS, +CNMI, +CMGL and +CMGR. You can begin the check by performing a test operation with each of the AT commands. For example, you can execute the command line "AT+CMGS=?" to check whether +CMGS is supported, like this:
AT+CMGS=?
OK
The final result code "OK" indicates the AT command +CMGS is supported. If the GSM/GPRS modem or mobile phone returns the final result code "ERROR", it means the command is not supported.
A quicker way is to copy and paste the following command line to the terminal program and execute it:
AT+CMGS=?;+CMSS=?;+CNMI=?;+CMGL=?;+CMGR=?
As an example, here shows the response returned from my Nokia 6021 to HyperTerminal after the execution of above command line:
AT+CMGS=?;+CMSS=?;+CNMI=?;+CMGL=?;+CMGR=?
+CNMI: (0-2),(0-3),(0,2,3),(0-2),(0,1)
+CMGL: (0-4)
OK
The return of the final result code "OK" indicates all AT commands under test are supported. If the final result code "ERROR" is returned, it means one or more AT commands are not supported.
Source Article : http://www.developershome.com/sms/
