How to Access the AT Command Line via AT Over COM on RobustOS Routers

How to Access the AT Command Line via AT Over COM on RobustOS Routers

Overview

This guide describes how to use the AT Over COM feature on Robustel RobustOS devices. This function allows users to send AT commands directly to the cellular module through the gateway's physical serial (COM) port. This is particularly useful for scenarios requiring manual cellular module control or sending SMS messages via serial integration.


What You'll Need

Before starting, ensure you have the following hardware and software ready to avoid interruptions:

  • Hardware List:
  • 1x Robustel Gateway (e.g., R3000) running RobustOS.
  • 1x Active SIM card with a valid SMS/Data plan.
  • 1x Serial cable (RS232 or RS485 depending on your model).
  • 1x Power supply for the gateway.


  • Software/Firmware:
  • "AT Over COM" App (Note: If the "AT Over COM" App is not available in your system, please contact Robustel technical staff to obtain it.)
  • A serial terminal tool installed on your PC (e.g., SecureCRT).


Step-by-Step Configuration Guide

Step 1: Verify Cellular Connectivity

Ensure the device is connected to the network before attempting to send AT commands related to cellular functions.

  1. Log into the Web GUI.
  2. Navigate to Interface > Link Manager.
  3. Confirm the Status >Link Status shows Connected and an IP address is assigned.



Step 2: Install the AT Over COM App

The feature requires a specific application to be installed on RobustOS.

  1. Navigate to System > App Center.
  2. In the App Install section, click Choose File and select the downloaded "AT Over COM" .rpk file.
  3. Click Install.


Step 3: Enable AT Over COM Services

  1. Navigate to Services > AT Over COM.
  2. Set Enable to ON.
  3. Configure the Serial Settings to match your PC's connection (Default is usually Baud Rate: 115200, Data Bits: 8, Stop Bits: 1, Parity: None).
  4. Click Submit and then Save & Apply.



Step 4: Configure PC Terminal Software

  1. Connect the gateway to your PC via the serial cable.
  2. Open Device Manager on your PC to identify the COM Port number (e.g., COM3).

  1. Open SecureCRT (or a similar tool) and create a new Serial connection.
  2. Match the parameters set in the gateway: Port: COM3, Baud rate: 115200, Data bits: 8, Parity: None, Stop bits: 1.
  3. Ensure Flow Control is disabled.


Verification & Testing

Testing Basic AT Communication

  1. In your terminal window, type AT and press Enter.
  2. The module should reply with OK.

Note: The characters you type may be hidden depending on your terminal settings.


Sending an SMS via AT Commands

To confirm full functionality, you can send a test SMS:

  1. Type AT+CMGF=1 (Sets SMS to Text Mode) and press Enter.
  2. Type AT+CMGS="+[Phone Number]" (Replace with your actual mobile number) and press Enter.
  3. Type your message (e.g., Welcome to Robustel).

  1. Press Ctrl+Z to send the message.
  2. Verification is successful if you receive the message on your phone.


Troubleshooting / FAQ

  • Q: My terminal does not show "OK" when I type "AT". What should I check?
  • A: First, verify the physical serial cable connection and ensure the Baud Rate matches the device settings. Because input characters may be hidden by default, you can enter the command ATE1 and press Enter to enable the local echo of AT commands.


  • Q: Can I use RS485 instead of RS232?
  • A: Yes, provided you change the Com Type in the AT Over COM Settings to match your physical wiring.


Revision History

Version

Date

Author

Changes

1.0

2026-01-15

Steven

Initial document.


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