Must-Read for Overseas LTE Modem Users: Quick Start Guide to AT Command Set
In an intelligent transformation project at an iron mine in Queensland, Australia, engineers swiftly diagnosed the issue of insufficient signal strength in LTE Modem devices using the "AT+CSQ" command. Within just 15 minutes, they adjusted the antenna position, avoiding hours of troubleshooting. This case highlights the core value of the AT command set in the Industrial Internet of Things (IIoT)—achieving efficient device configuration and fault localization through standardized commands. This article will systematically analyze the application methods of the AT command set for LTE modems, incorporating real-world scenarios of overseas users.
1. AT Command Set: The "Neural Language" of LTE Modems
The AT command set is a standardized protocol for communication between LTE modems and external devices, with its core value reflected in three aspects:
Protocol Compatibility: Supports the 3GPP TS 27.007 standard and vendor-extended commands, adaptable to mainstream global communication modules.
Debugging Efficiency: Enables real-time parameter querying and modification through a "question-and-answer" interaction.
Remote Management: Supports three command delivery methods: serial port, network, and SMS.
Taking USR-G771 from USR IOT (Jinan YouRen IoT) as an example, its AT command set encompasses 12 major functional modules, including basic parameter querying, network configuration, and serial port settings. In Australian mining scenarios, engineers can swiftly configure the TCP connection between the LTE Modem and SCADA system using the "AT+SOCKA" command, reducing the parameter setting process from 30 minutes to just 3 minutes.
2. Core Command Analysis: From Beginner to Expert
2.1 Device Status Diagnosis
Signal Strength Query:
AT+CSQ
Return Example: +CSQ:28,99
The value 28 indicates signal strength (range 0-31), with 99 being an unused field.
Australian mining site test data shows that a signal strength ≥15 ensures data transmission stability.
Module Information Query:
AT+INFO
Return Example: +OK=USR-G771,V1.0.3,20240520
Obtains key information such as device model, firmware version, and production date.
During device failures, this command aids in quickly identifying firmware version issues.
2.2 Network Configuration
APN Setting (Example for Telstra Network in Australia):
AT+APN="telstra.internet"
Return: +OK
Correct APN parameters must be configured according to operator requirements.
Incorrect configuration will prevent the device from accessing the network.
Multi-Center Server Configuration:
AT+SVRCNT=2
AT+IPAD1="192.168.1.100"
AT+PORT1=5000
AT+IPAD2="backup.server.com"
AT+PORT2=5000
Supports simultaneous connection to primary and backup servers, enhancing system reliability.
In remote Australian mining areas, this feature prevents device offline status due to single network failures.
2.3 Serial Port Parameter Settings
Baud Rate Modification:
AT+IPR=115200
Return: +OK
Must match the host computer software settings.
Australian lithium mine project tests reveal that baud rate mismatches cause over 30% data packet loss.
Data Bit and Parity Bit Settings:
AT+DATABIT=8
AT+PARITY=NONE
AT+STOPBIT=1
3. Typical industrial scenario configuration: 8 data bits, no parity, 1 stop bit.
Incorrect configurations may lead to communication interruptions.
Practical Applications in Typical Scenarios
Scenario 1: Remote Debugging of Equipment in Australian Mining Areas
Problem Description: A LTE Modem device at a gold mine fails to upload data, with no professional engineers on-site.
Solution:
Send diagnostic commands via SMS:
usr.cn#AT+CSQ[0D][0A]
Return: +CSQ:5,99
A signal strength of 5 (<10) indicates the need for antenna position adjustment.
Remotely modify APN parameters:
usr.cn#AT+APN="mines.apn"[0D][0A]
Return: +OK
Device communication is restored within 30 minutes.
Scenario 2: Multi-Device Collaborative Control in Western Australian Lithium Mines
Requirement: Achieve real-time linkage between 128 hydraulic supports and a coal mining machine.
Solution:
Configure LTE Modem Socket multi-connections via AT commands:
AT+SOCKCNT=4
AT+SOCK1="192.168.1.10",5000,TCPC
AT+SOCK2="192.168.1.11",5000,TCPC
...
Set data forwarding rules:
AT+SOCKFWD=1,2
Enables real-time transmission of support status data to the control center.
System response time is reduced from 2s in traditional solutions to 200ms.
4. Solutions to Common Problems
4.1 No Response to Commands
Troubleshooting Steps:
Verify command format correctness (must start with "AT").
Confirm device is in command mode (USR-G771 requires sending "+++a" to enter).
Validate matching serial port parameters (baud rate, data bits, etc.).
Case: An iron mine engineer repeatedly sent "AT+CSQ" without response, eventually discovering the serial port baud rate was incorrectly set to 9600 (actual should be 115200).
4.2 Parameter Modification Failure
Typical Error:
AT+IPR=200000
Return: ERROR
Reason: USR-G771 supports a maximum baud rate of 115200bps.
Solution: Refer to the device manual for supported parameters.
4.3 Network Connection Abnormalities
Diagnostic Process:
Send "AT+CGATT?" to check network attachment status.
Send "AT+CSQ" to check signal strength.
Send "AT+SOCKSTA" to check Socket connection status.
Australian mining site test data: TCP connection success rate drops by 67% when signal strength <10.
Advanced Application Techniques
5.1 Batch Configuration Management
Implement multi-device parameter synchronization through scripting:
python
| # Example: Batch modify APN parameters |
| devices = ["LTE Modem001","LTE Modem002","LTE Modem003"] |
| fordevindevices: |
| send_command(dev,"usr.cn#AT+APN=\"new.apn\"[0D][0A]") |
