Quick Reference

AT Commands

AT commands are text-based instructions sent to a modem (communication module) over a serial interface. They are used to control the modem's behavior, check its status, and configure its connection settings. The name comes from the word "attention" - each command begins with the prefix AT to signal the modem that an instruction follows.

AT commands are standardized by 3GPP and ETSI, which means that a core set of commands works across modems from different manufacturers. However, each manufacturer may also provide additional vendor-specific commands. This page covers the generic, standards-based commands that apply to most cellular modems.

Overview

When working with cellular IoT devices, you may need to interact directly with the modem to:

• Verify that the modem detects the SIM and reads its identity
• Check whether the modem is registered to a network
• Inspect the signal quality at the device's location
• View or change the selected network operator
• Configure the APN (Access Point Name) and data connection settings
• Enable or disable modem functionality

AT commands give you direct control over these operations, making them essential for initial device setup, troubleshooting connectivity issues, and verifying modem behavior in the field.

Accessing the AT Command Interface

To send AT commands, you need a serial or USB connection between your computer (or terminal) and the modem. The typical setup involves:

1. Connect your computer to the modem's serial or USB interface using an appropriate cable or adapter.
2. Open a serial terminal application and connect to the correct port at the modem's configured baud rate.

Common serial terminal applications include:

• Windows: PuTTY or Tera Term, connected to the COM port where the modem is attached.
• macOS / Linux: The screen or minicom command, connected to a device file such as /dev/tty.usbmodem* or /dev/ttyUSB*. For example: screen /dev/ttyUSB0 115200 or minicom -D /dev/ttyUSB0 -b 115200.

Some devices also provide access to the AT command interface through a built-in console, web interface, or debug port. Check your device's documentation for details.

Command Format and Responses

Every AT command starts with the AT prefix and ends with a carriage return. Commands are not case-sensitive, but uppercase is conventional.

There are three standard forms for most commands:

After you send a command, the modem responds with one of the following:

• OK indicates the command was accepted and executed successfully.
• ERROR or +CME ERROR: <code> indicates the command failed. The error code provides details about what went wrong. By default, some modems return only a generic ERROR response. Setting AT+CMEE=2 configures the modem to return readable error descriptions instead of numeric codes, which can simplify troubleshooting. Look up CME error codes in your modem's AT command manual for specific details about each error.

Safety Considerations

Before sending AT commands, be aware of the following:

• Persistent settings: Some commands change modem settings that survive a reboot. Incorrect values can affect the modem's ability to connect until they are corrected.
• Connection loss: Commands such as AT+CFUN=0 disable the modem's radio, which immediately drops any active connection. If you are connected to the device remotely, this can make it unreachable.
• Network disruption: Changing the APN, authentication, or operator selection to incorrect values can prevent the modem from reconnecting to the network.
• Read before write: Use the read form (AT+CMD?) before using the write form (AT+CMD=<value>) so you understand the current configuration before changing it.

Common AT Commands

The following commands are defined by 3GPP standards and are supported by most cellular modems. For each command, the expected response format and key values to look for are described.

Error Reporting

AT+CMEE=2

Enable verbose error reporting. By default, some modems return only a generic ERROR response when a command fails. This command configures the modem to return readable error descriptions, which simplifies troubleshooting.

AT+CMEE=2
OK

The available modes are:

Modem and SIM Identification

ATI

Display modem identification information.

ATI
Quectel
BG96
Revision: BG96MAR02A07M1G

OK

The response format varies by manufacturer but typically includes the modem model and firmware version.

AT+CIMI

Display the IMSI (International Mobile Subscriber Identity) stored on the SIM.

AT+CIMI
295050012345678

OK

The response should be a 15-digit number that matches the IMSI of your Soracom IoT SIM.

AT+CCID

Display the ICCID (Integrated Circuit Card Identifier) of the SIM.

AT+CCID
+CCID: 8942310000012345678

OK

The response should be a 19- or 20-digit number that matches the ICCID of your Soracom IoT SIM.

AT+CPIN?

Check the SIM card status, including whether a PIN is required.

AT+CPIN?
+CPIN: READY

OK

Common response values:

If the response is anything other than READY, the modem cannot register to a network. Verify that the SIM is correctly inserted and that the correct PIN has been provided.

Terminal / Command Session

ATE

Enable or disable command echo.

ATE1
OK

ATE1 enables echo, causing the modem to send back each character it receives before processing the command. ATE0 disables modem echo, so only the command response is shown. Note that some terminal programs may display local echo independently of the modem setting.

Disabling echo is typically preferred when sending commands programmatically from scripts or software, while enabling echo can be helpful for interactive debugging in a terminal.

Modem Functionality

AT+CFUN?

Query the current modem functionality level.

AT+CFUN?
+CFUN: 1

OK

A value of 1 means full functionality is enabled (radio on). A value of 0 means the radio is disabled. A value of 4 means flight mode (radio off, SIM accessible).

AT+CFUN=0

Disable the modem radio (minimum functionality). The modem deregisters from the network and drops any active data connection.

AT+CFUN=0
OK

AT+CFUN=1

Enable full modem functionality (turn on the radio).

AT+CFUN=1
OK

AT+CFUN=4

Enable flight mode. The radio is turned off, but the SIM remains accessible. This is useful when you need to read SIM data or change modem configuration without maintaining a network connection.

AT+CFUN=4
OK

Network Operator Selection

AT+COPS=?

Scan for available network operators. This command typically takes 2-3 minutes to complete.

AT+COPS=?
+COPS: (2,"T-Mobile","T-Mo","310260",7),(1,"AT&T","AT&T","310410",7)

OK

Each entry follows the format (status,"long name","short name","PLMN",access technology). The status value indicates the operator's availability:

The access technology value indicates the network type. The most common values are listed below; refer to 3GPP TS 27.007 for the full set:

In the example above, T-Mobile (status 2) is the currently registered operator on 4G, and AT&T (status 1) is available on 4G.

AT+COPS?

Display the currently selected network operator.

AT+COPS?
+COPS: 0,0,"T-Mobile"

OK

The response format is +COPS: <mode>,<format>,"<operator>". The mode indicates how the operator was selected:

The format indicates how the operator name is displayed (0 = long alphanumeric, 1 = short alphanumeric, 2 = numeric PLMN). Use AT+COPS=3,<format> to change the display format.

AT+COPS=0

Return to automatic network operator selection.

AT+COPS=0
OK

AT+COPS=1,2,"<PLMN>"

Manually select a network operator by its PLMN code. For example, to select AT&T in the United States:

AT+COPS=1,2,"310410"
OK

The parameters are: 1 = manual selection mode, 2 = numeric PLMN format.

AT+COPS=3,<format>

Set the format used when displaying operator information in AT+COPS? responses, without changing the current operator selection. The format values are:

For example, to display the operator as a numeric PLMN code:

AT+COPS=3,2
OK

AT+COPS?
+COPS: 0,2,"310260"

OK

AT+COPS=4,2,"<PLMN>"

Attempt manual operator selection first, and fall back to automatic selection if the manual selection fails. This is useful when you prefer a specific operator but want the modem to find an alternative if that operator is unavailable.

AT+COPS=4,2,"310410"
OK

The parameters follow the same format as manual selection (AT+COPS=1), but with mode 4 instead of 1.

AT+CPLS and AT+CPOL

These commands allow you to view and configure the UPLMN (User-controlled PLMN selector with Access Technology) list stored on the SIM. The UPLMN list defines which network operators the modem should prefer when searching for networks, and which radio access technologies to use with each operator.

AT+CPLS selects which PLMN list subsequent AT+CPOL commands will read or modify:

AT+CPOL? displays the entries in the currently selected PLMN list.

AT+CPOL= adds or modifies entries in the UPLMN list. The parameters are: slot number, format (2 = numeric PLMN), PLMN code, followed by flags for each supported radio access technology.

For example, to configure the UPLMN list with T-Mobile US on all radio access technologies and AT&T on 4G only:

AT+CPLS=0
OK

AT+CPOL=1,2,"310260",1,0,1,1
OK

AT+CPOL=2,2,"310410",0,0,0,1
OK

The radio access technology flags in AT+CPOL are positional:

A value of 1 enables the radio access technology and 0 disables it. In the example above, T-Mobile is configured with 2G, 3G, and 4G enabled (1,0,1,1), while AT&T is configured with 4G only (0,0,0,1).

Network Registration

AT+CREG?

Check network registration status (2G/3G networks).

AT+CREG?
+CREG: 0,5

OK

AT+CEREG?

Check network registration status (4G/LTE networks).

AT+CEREG?
+CEREG: 0,5

OK

In both responses, the second value indicates the registration status:

When using a Soracom IoT SIM with a global coverage plan such as plan01s, the expected value is 5 (registered, roaming). For plans with local coverage, the expected value is 1 (registered, home network).

Signal Quality

AT+CSQ

Query signal strength (RSSI) and bit error rate.

AT+CSQ
+CSQ: 15,99

OK

The first value is the RSSI index:

The second value is the bit error rate. A value of 99 means it is not available, which is normal for most network types.

AT+CESQ

Query extended signal quality measurements. This command provides more detailed metrics than AT+CSQ, including values specific to 3G and 4G networks.

AT+CESQ
+CESQ: 99,99,255,255,20,55

OK

The response contains six values:

Values of 99 or 255 indicate that the measurement is not available, which is expected for metrics that do not apply to the current network type. In the example above, the device is connected to a 4G network, so only RSRQ and RSRP contain valid measurements.

For RSRP, higher values indicate stronger signal. The approximate dBm equivalent is value - 141:

For RSRQ, higher values indicate better signal quality. The approximate dB equivalent is (value / 2) - 20:

APN and Data Connection

AT+CGDCONT?

Query the current PDP context configuration.

AT+CGDCONT?
+CGDCONT: 1,"IP","soracom.io","",0,0

OK

AT+CGDCONT=1,"IP","soracom.io"

Define a PDP (Packet Data Protocol) context with Soracom's APN settings. This saves the configuration to PDP context slot 1.

AT+CGDCONT=1,"IP","soracom.io"
OK

AT+CGAUTH=1,2,"sora","sora"

Set CHAP (Challenge-Handshake Authentication Protocol) authentication credentials for PDP context 1. The parameters are: 1 = PDP context identifier, 2 = CHAP authentication type, followed by the username and password.

AT+CGAUTH=1,2,"sora","sora"
OK

AT+CGATT?

Check whether the modem is attached to the packet domain.

AT+CGATT?
+CGATT: 1

OK

A value of 1 means the modem is attached. A value of 0 means it is not attached.

AT+CGACT?

Check whether a PDP context is activated.

AT+CGACT?
+CGACT: 1,1

OK

The first value is the PDP context identifier and the second value is the activation status. 1 = activated, 0 = deactivated.

AT+CGPADDR=1

Display the IP address assigned to PDP context 1.

AT+CGPADDR=1
+CGPADDR: 1,"10.0.123.45"

OK

If the modem has been assigned an IP address, the data connection is established and the device should be able to send and receive data.

Generic vs. Manufacturer-Specific Commands

The commands described above are defined by 3GPP standards and are supported by most cellular modems. However, modem manufacturers often provide additional proprietary commands that offer:

• More detailed diagnostic information (such as serving cell details, band information, or connection quality metrics)
• Simplified configuration for device-specific features
• Access to hardware-specific functionality not covered by the 3GPP standard

For the full set of commands available on your modem, refer to the AT command manual published by your modem's manufacturer. If you cannot find the manual, contact the manufacturer directly.

Example: Generic vs. Vendor-Specific Signal Information

The generic AT+CSQ command returns a basic signal strength index:

AT+CSQ
+CSQ: 15,99

OK

This provides a general indication of signal strength but limited detail. Some modem manufacturers offer proprietary commands that return much more detailed information. For example, a vendor-specific command might return the serving cell details including the frequency band, channel number, and additional signal quality measurements such as SINR:

AT+VENDORCMD="servingcell"
+VENDORCMD: "servingcell","NOCHANGE","LTE","FDD",310,260,BFD3,318E202,100,7,5,5,-95,-8,15,25

OK