AT Commands (AT-SMS)

AT-SMS Protocol

Introduction

AT-SMS protocol is a private set of AT commands supported by Advantech cellular routers. It can be used to access the cellular module in the router directly via AT commands, work with short messages (SMS), and retrieve cellular module state information and settings. AT commands listed here can be sent to the router via TCP or via a serial line. This functionality must be enabled in the router configuration.

Caution

Only the commands supported by Advantech routers are listed in this application note. For other AT commands, the OK response is always sent. There is no support for processing complex AT commands, so in such cases the router sends an ERROR response.

Enabling AT-SMS Protocol

In the web interface of the router, navigate to Services → SMS in the Configuration section. Enable AT-SMS protocol on the desired interface — serial or TCP. Click the Apply button.

Tips

You can test the AT-SMS protocol using any TCP client (Enable AT-SMS protocol over TCP must be enabled). In the figure below, an example shows a test using Hercules TCP Client with the configuration from the previous figure (TCP port 54321). The response to the AT+CMGF? command is "0", indicating that SMS messages are in PDU mode.

Example of sending AT command via TCP client

Caution

Note: When Enable remote control via SMS is activated on the router, any received SMS is immediately deleted after processing! (See the figure above.) This behavior might cause confusion if you intend to use the AT-SMS protocol to read received SMS messages. For detailed information, refer to your router's Configuration Manual. If remote control via SMS is enabled, the command contained in the SMS is executed, and then the SMS is deleted. If an unknown command is received, the script /var/scripts/sms is executed, and then the SMS is deleted.

Caution

AT commands sent to the router's cellular module using gsmat and gsmat2 (as described in the Command Line Interface Application Note, e.g. via SSH) are not processed as AT-SMS protocol commands. These are general AT commands, and their support may vary among different cellular module models.

Available AT Commands

ATE

The ATE<value> command determines whether or not the device echoes characters. By default, this function is disabled, but it may be useful for debugging.

"<value>" is 0 — characters are not echoed
"<value>" is 1 — characters are echoed

ATE1             <press Enter key>
OK

AT+CMGF

To set the presentation format of short messages, use the AT+CMGF=<mode> command.

"<mode>" is 0 — PDU mode
"<mode>" is 1 — text mode

AT+CMGF=1        <press Enter key>
OK

Tips

To determine the SMS format currently set, execute AT+CMGF?.

AT+CMGS

This command allows you to send a short message to a specified number. After issuing the command AT+CMGS="<number>" and pressing the Enter key, wait for the prompt >. At that point, type your message. The message is sent by pressing CTRL+Z (this may take some time). To cancel message composition, press the Esc key.

AT+CMGS="+420465717171"                    <press Enter key>
>Hello World!                              <CTRL+Z shortcut key>
OK

If you want to send an SMS in PDU mode, you must first convert your message text to PDU format, including the recipient's phone number (e.g., using an online converter).

The example below shows the string "test" sent to the phone number +420465717171. In PDU mode, sending an SMS is similar to text mode, but instead of a phone number, the binary length of the PDU message is provided:

AT+CMGS=18                                 <press Enter key>
>0011000C912440561717170000FF04F4F29C0E    <CTRL+Z shortcut key>
OK

AT+CMGW

This command allows you to write a short message to SIM storage. After issuing the command AT+CMGW="<length>" (where "<length>" specifies the maximum message length in bytes) and pressing the Enter key, wait for the prompt >. Then type your message. The message is stored by pressing CTRL+Z (this may take some time). To cancel SMS composition, press the Esc key. The response includes the storage location of the message.

AT+CMGW="140"         <press Enter key>
>Hello World!         <CTRL+Z shortcut key>
+CMGW: 2

AT+CMSS

The AT+CMSS command sends a message from SIM storage at the specified <index>. The index corresponds to the value returned by the AT+CMGW command. The response is a reference value.

AT+CMSS=2             <press Enter key>
+CMSS: 12

AT+CMGL

The AT+CMGL command is used to list messages with a specific status from a message storage area. When you use the command in the form AT+CMGL="ALL", it returns a list of all stored messages. Note that if a message is "received unread", retrieving it with AT+CMGL changes its status to "received read".

+CMGL: "<index>", "<status>", "<sender number>", ,"<date>","<time>"
   SMS text

Parameters:

"<index>" — location of the message in the message storage area
"<status>" — specifies the message status:
- REC UNREAD — received unread
- REC READ — received read
- STO UNSENT — stored unsent
- STO SENT — stored sent
- ALL — lists all messages (Note: This option does not work in PDU mode. Use AT+CGML=4 in PDU mode instead.)
"<sender number>" — telephone number from which the message was received
"<date>" — date when the message was received
"<time>" — time when the message was received

AT+CMGL="ALL"                   <press Enter key>
+CMGL: 1,"REC UNREAD","+420465717171", ,"08/02/02, 10:33:26+04"
Hello World!

AT+CMGR

The AT+CMGR command is used to read a message from a message storage area. The message's location is specified by an <index> number. If the message is "received unread", retrieving it changes its status to "received read". Each message is displayed in the following format:

+CMGR: "<index>","<status>","<sender number>", ,"<date>","<time>"
   SMS text

AT+CMGR=1                 <press Enter key>
+CMGR: 1,"REC READ","+420465717171", ,"08/01/12, 9:48:04+04"
Hello World!

AT+CMGD

This command deletes a message at the specified <index> location.

AT+CMGD=1                 <press Enter key>
OK

AT+CPMS

To select SMS memory storage types for reading, writing, deleting, sending, or receiving messages, use the AT+CPMS command. For a SIM card, use "SM". The expected response is in the following format:

+CPMS: "<used1>","<max1>","<used2>","<max2>","<used3>","<max3>",

Here, the used values indicate the current number of messages stored, and the max values indicate the maximum number of messages that can be stored.

AT+CPMS="SM","SM"         <press Enter key>
+CPMS: 1,10,1,10
OK

AT+CSCA

This command sets the short message service center (SMSC) number used for sending SMS text messages.

AT+CSCA="+491710760000"         <press Enter key>
OK

AT+CSCS

To change the character set, use the AT+CSCS=<set> command. If you enter AT+CSCS=?, the response lists the supported character sets.

AT+CSCS=?                       <press Enter key>
+CSCS: ("GSM","IRA","HEX")

AT+CSCS="HEX"                   <press Enter key>
OK

AT+CPIN

The AT+CPIN? command queries whether a PIN code is required. If the response is +CPIN: READY, no PIN is needed and the SIM card is ready for use. If the SIM card requires a PIN (response: +CPIN: SIM PIN), enter it using AT+CPIN=<PIN>. If the PIN is entered incorrectly more than three times, the SIM card is blocked and a PUK code is required (response: +CPIN: SIM PUK).

AT+CPIN="2654"                  <press Enter key>
OK

AT+CIMI

Executing this command returns the International Mobile Subscriber Identity number (IMSI). This unique 15-digit identifier is assigned to the SIM card by the mobile operator. The first 3 digits represent the Mobile Country Code (MCC), followed by the Mobile Network Code (MNC) — either 2 digits (European standard) or 3 digits (North American standard), with the length determined by the MCC value — and the remaining digits form the Mobile Subscription Identification Number (MSIN).

AT+CNUM

Executing this command returns the phone number of the SIM card, if it is stored on the SIM (by the mobile operator). Note that typically, the mobile operator does not store a phone number on the SIM card.

AT+CREG

The AT+CREG command displays network registration status. When you execute AT+CREG?, the response appears in the following format:

+CREG: "<n>","<stat>",

Here, <n> corresponds to one of the following values:

0 — disable network registration unsolicited result code
1 — enable network registration unsolicited result code

And <stat> (registration status) corresponds to:

0 — not registered, not searching for a new operator
1 — registered, home network
2 — not registered, currently searching for a new operator
3 — registration denied
4 — unknown
5 — registered, roaming

AT+CREG?         <press Enter key>
+CREG: 0,1

AT+COPS?

The AT+COPS? command is used to identify available mobile networks. After executing the command and pressing Enter, the response appears in the following format:

+COPS: "<mode>","<format>","<operator>",

Where <mode> specifies the registration mode:

0 — automatic
1 — manual
2 — de-register from network
4 — manual/automatic (if manual selection fails, automatic mode is used)

And <operator> displays the operator identity in the format specified by <format>:

0 — long alphanumeric format
1 — short alphanumeric format
2 — numeric format

AT+COPS?                <press Enter key>
+COPS: 0,0,"O2 - CZ"

AT+CSQ

This command returns the signal strength of the registered network. The response is in the form +CSQ: <rssi>,<ber>, where <rssi> represents the received signal strength (ranging from 0 for -113 dBm or lower, to 31 for -51 dBm or higher, or 99 if unknown), and <ber> represents the channel bit error rate. The BER can be measured only during an active call; at all other times its value is 0 or 99. When measurable, <ber> ranges from 0 to 7.

AT+CSQ            <press Enter key>
+CSQ: 28,99

ATI

Use the ATI<value> command to transmit manufacturer-specific information about the device. The <value> parameter selects among various types of identification information, starting at 0 (which corresponds to AT+GMM).

AT+CGMI

Executing this command returns the manufacturer identity of the cellular module.

AT+CGMI                  <press Enter key>
+CGMI: Quectel

(Example for a router with the Quectel EC25 cellular module.)

AT+GMI

See the previous command AT+CGMI.

AT+CGMM

Executing this command returns the manufacturer-specific model identity of the cellular module.

AT+CGMM              <press Enter key>
+CGMM: "EC25"

(Example for a router with the Quectel EC25 cellular module.)

AT+GMM

See the previous command AT+CGMM.

AT+CGMR

Executing this command returns the manufacturer-specific model revision identity of the cellular module.

AT+CGMR                  <press Enter key>
+CGMR: EC25EUGAR06A03M4G

(Example for a router with the Quectel EC25 cellular module.)

AT+GMR

See the previous command AT+CGMR.

AT+CGSN

This command returns the serial number of the cellular module.

AT+CGSN                  <press Enter key>
+CGSN: 865546040009660

Item	Description
AT+CGMI	Returns the manufacturer specific identity
AT+CGMM	Returns the manufacturer specific model identity
AT+CGMR	Returns the manufacturer specific model revision identity
AT+CGPADDR	Displays the IP address of the Mobile WAN interface
AT+CGSN	Returns the product serial number
AT+CIMI	Returns the International Mobile Subscriber Identity number (IMSI)
AT+CMGD	Deletes a message from the location
AT+CMGF	Sets the presentation format of short messages
AT+CMGL	Lists messages of a certain status from a message storage area
AT+CMGR	Reads a message from a message storage area
AT+CMGS	Sends a short message from the device to a specified telephone number
AT+CMGW	Writes a short message to SIM storage
AT+CMSS	Sends a message from a specified SIM storage location
AT+CNUM	Returns the phone number, if available (stored on SIM card)
AT+COPS?	Identifies the available mobile networks
AT+CPIN	Queries the SIM card state and allows PIN entry
AT+CPMS	Selects SMS memory storage types for message operations
AT+CREG	Displays network registration status
AT+CSCA	Sets the short message service center (SMSC) number
AT+CSCS	Selects the character set
AT+CSQ	Returns the signal strength of the registered network
AT+GMI	Returns the manufacturer specific identity
AT+GMM	Returns the manufacturer specific model identity
AT+GMR	Returns the manufacturer specific model revision identity
AT+GSN	Returns the product serial number
ATE	Determines whether or not the device echoes characters
ATI	Transmits the manufacturer specific information about the device