What are mobile AT commands? And how to use them?

As mobile technology continues to evolve, engineers are always on the lookout for new ways to interact with mobile devices. One way to achieve this is through the use of AT commands. These commands allow engineers to communicate with mobile devices directly and control their functions. In this article, we will discuss what AT commands are, how they work, and how to use them to interact with mobile devices.

What are AT Commands?

AT commands are short strings of characters that are used to interact with modems, mobile devices, and other communication devices. The term AT stands for Attention, which is the prefix used to initiate a command. These commands are typically sent using a serial interface or a USB connection. They are used to configure, control, and query various settings on mobile devices.

AT commands are standardized by the ITU-T, which is a UN agency that deals with international telecommunications standards. The standard defines a set of basic commands that can be used to communicate with modems and other communication devices. These commands include basic commands for dialing, hanging up, and controlling the flow of data.

How Do AT Commands Work?

AT commands work by sending a sequence of characters to a mobile device. These commands are interpreted by the device’s firmware, which then executes the requested action. The firmware is a set of software instructions that control the device’s hardware. It is responsible for handling all the low-level tasks of the device, such as reading and writing to the device’s memory, controlling the device’s peripherals, and communicating with other devices.

When an AT command is received by a mobile device, the firmware checks the command’s syntax and executes the appropriate action. If the command is valid, the device will respond with an OK message. If the command is invalid, the device will respond with an error message.

AT commands are typically sent using a serial interface. This interface allows engineers to send and receive data from a mobile device using a standard communication protocol. The protocol used is typically RS-232, which is a standard for serial communication.

How to Use AT Commands

Using AT commands requires some basic knowledge of the command syntax and the device’s firmware. Different devices may have different command sets, so it’s important to refer to the device’s documentation to ensure that the correct commands are being used.

To use AT commands, engineers need to connect their device to a computer using a serial or USB interface. They can then use a terminal emulator program to send commands to the device. The terminal emulator program allows engineers to type in commands and see the device’s response.

One popular terminal emulator program is PuTTY, which is a free and open-source program that can be used to communicate with mobile devices. PuTTY supports serial and USB interfaces and allows users to send and receive data using a terminal interface.

When using PuTTY, engineers can open a serial connection to the device and start sending commands. They can use the AT command prefix to initiate a command and then type in the command’s syntax. For example, to check the device’s signal strength, engineers can send the following command:

How to Use AT Commands

Using AT commands is straightforward with the right tools. Here’s a basic guide:

1. Connect the Device: Connect your device to a computer via a serial or USB interface.
2. Open a Terminal Emulator: Use a terminal emulator, like PuTTY, which is free and supports serial/USB interfaces.
3. Start Sending Commands: Open the connection in PuTTY, initiate commands with "AT," and type in the desired command syntax.

Example: To check signal strength, type:

Copy code:

This command asks the device to report its signal strength in decibels. The device will respond with a message that indicates the signal strength. Engineers can then use this information to determine the quality of the device’s connection.

Some common AT commands that can be used with mobile devices include:

• AT+CGSN – Query the device’s IMEI number
• AT+CIMI – Query the device’s IMSI number
• AT+CPIN – Enter the device’s SIM PIN
• AT+COPS – Set the device’s operator
• AT+CREG – Register the device on the network
• AT+CSQ – Query the device’s signal strength
• AT+CSMP – Set the device’s SMS parameters

Practical Applications

Engineers use AT commands for various purposes, such as troubleshooting network issues, configuring IoT devices, and optimizing device settings. These commands allow for efficient testing and quick adjustments without a graphical interface, making them invaluable for field diagnostics and remote device management.