[OpenWrt Wiki] How to send AT commands to device (2024)

AT commands (“attention commands” formally, the Hayes command set), are used to communicate directly with a modem device and configure it.

From OpenWrt

To send AT commands directly from OpenWrt, you can simply use echo to send them to the right device. However, you will not get any errors, confirmation or any other answer from the modem.

A better solution is using a proper terminal application like picocom, which can both send commands and print the modem's answers. There are other alternatives available like socat.

Once the appropriate serial driver is loaded (typically - kmod-usb-serial-option), the modem will expose a number of /dev/ttyUSBx interfaces. Usually only one or two of them will respond to AT commands.

As an example, popular Quectel EP06 LTE modem will create 4 serial devices, /dev/ttyUSB0 through to /dev/ttyUSB3.

To find the serial devices added to the system, try looking through logread and/or dmesg output. Something like the following may help:

dmesg | grep -A 1 -B 12 ttyUSB

For some modems ttyACM devices will be created instead of ttyUSB.

picocom

picocom is a simple terminal program that is installed in a standard way with opkg install picocom or through the web interface.

Sample command line:

picocom /dev/ttyUSB2

Adding --q on the command line will suppress extra output with some help and other information.

socat

socat will open a prompt where you can enter AT commands (see examples in the section below).

Here is a command line example:

socat - /dev/ttyUSB2,crnl

In this example socat will send a carriage return (cr) and a new line (nl) after each command.

To quit socat, use ctrl+C.

echo

See examples below. echo -e is used to send escaped characters such as quotation marks.

Alternative solution - use echo with socat: echo -e ATI | socat - /dev/ttyUSB2,crnl

From a computer

To send ATcommands to a LTE modem, you need to first connect the device/modem to the computer, most likely using an adapter (built-in modem slots are very rare these days) and access it with a COM terminal.

If you are not familiar with using COM terminals, you might want to use a graphical tool like: CuteCom or minicom. Installation of these are beyond the scope of this page.

These settings should work fine:

Device: /dev/ttyUSB0Connection: 115200 @ 8-N-1Line end: CR

Examples of AT commands

To test things are working, you can issue a standard ATI command which should return basic information such as brand, model and firmware revision.

AT+CSQ can be used to get signal strength. The values returned are the RSSI (received signal strength indication, higher is better) and BER (bit error rate, lower is better)

Huawei E392

Send: ATOKSend: AT^SETPORT=?Recieve: 1:MODEMRecieve: 2:PCUI Recieve: 3:DIAGRecieve: 4:PCSCRecieve: 5:GPSRecieve: 6:GPS CONTROLRecieve: 7:NDISRecieve: A:BLUE TOOTHRecieve: B:FINGER PRINTRecieve: D:MMSRecieve: E:PC VOICERecieve: A1:CDROMRecieve: A2:SDRecieve: OKSend: AT^SETPORT?Recieve: A1,A2;1,2,3,A1,A2Recieve: OKSend: AT^SETPORT="A1;2,7,A2"Recieve: OKSend: AT^SETPORT?Recieve: A1;2,7,A2Recieve: OK

Explanations:

AT^SETPORT=? - Lists the Available interfaces and their numbers AT^SETPORT? - Show current configuration AT^SETPORT="A1;2,7 - Sets configuration.

Modem configuration is split into 2 parts: before ; and after.

Once a modem is plugged-in, it should declare itself in first configuration (normally with at least: A1 - virtual CD drive with Drivers and application). If the drivers are installed, they will see the modem and issue a special command to switch to a “working” configuration - this is 2,7 interfaces in this example.

[OpenWrt Wiki] How to send AT commands to device (1) Warning: Never turn Off the AT Command interface! (“PCUI” in Huawei terms) You will lose the ability to access modem with terminal and change the configuration.

You can add more interfaces to be active i.e. SD card:

AT^SETPORT="A1,A2;2,7,A2"

If you get an ERROR, maybe the numerical mode is not sorted (16,2,7)→(2,7,16). If your device answers to set command with OK but AT^SETPORT? doesn't show your desired settings, you can try using space in between numerical modes(2,7) and alphabetical modes(A2) like so:

AT^SETPORT="A1,A2;2,7,A2"

Or with multiple modes:

AT^SETPORT="A1,A2;2,7,A1,A2"

Quectel modems

How to force LTE connection

Format:

AT+QCFG="nwscanmode"[,<scanmode>[,<effect>]]

Parameters

<scanmode> Number format, network search mode0 AUTO1 GSM only2 UMTS only3 LTE only<effect> Number format, when to take effect0 Take effect after UE reboots1 Take effect immediately

Examples:

Set modem to LTE only:

echo -e "AT+QCFG=\"nwscanmode\",3,1" > /dev/ttyUSB2

Set it back to “auto”:

echo -e "AT+QCFG=\"nwscanmode\",0,1" > /dev/ttyUSB2

Further references

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[OpenWrt Wiki] How to send AT commands to device (2024)

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