Detailed Explanation of AT Command Set for Serial to Ethernet Adapters: A Guide to Custom Message Formats and Trigger Rule Settings

In industrial IoT scenarios, serial to Ethernet adapter serve as the core hub connecting traditional serial devices to Ethernet networks, with their communication protocol flexibility and stability directly impacting data transmission efficiency. However, traditional serial to Ethernet adapter often face three major pain points: rigid message formats leading to poor compatibility, single trigger rules unable to meet complex scenario requirements, and a debugging process that relies on professional tools and is time-consuming and labor-intensive. This article will take the USR-N520 dual serial to Ethernet adapter as an example to provide an in-depth analysis of how to achieve custom message formats and trigger rules through the AT command set, helping enterprises break through technical bottlenecks and improve system integration efficiency.

1. Analysis of the Three Major Pain Points of Traditional Serial to Ethernet Adapters

1.1 Rigid Message Formats: Limited Device Compatibility

In a smart factory case, a customer needed to connect 200 truck scale instruments of different brands (supporting the Modbus RTU protocol) to a cloud platform. Traditional serial to Ethernet adapters only supported fixed frame header and frame tail formats, causing some instruments to be unable to parse data due to mismatched check bits. Eventually, an additional protocol conversion module had to be developed, increasing hardware costs by 30%.

1.2 Single Trigger Rules: Insufficient Scenario Adaptability

A logistics and warehousing project required sensor data to immediately trigger an alarm when the temperature exceeded limits or the device went offline. However, traditional devices only supported timed polling mode, resulting in an alarm delay of up to 15 minutes and causing cargo losses. Such scenarios urgently need an event-based dynamic response mechanism.

1.3 Debugging Reliance on Professional Tools: Low Operational Efficiency

During the deployment of an energy monitoring system, engineers had to carry equipment such as oscilloscopes and logic analyzers to the site for debugging, with a single maintenance session taking more than 4 hours. If remote parameter configuration could be achieved through AT commands, operational and maintenance costs could be significantly reduced.

2. Core Advantages of the USR-N520 Serial to Ethernet Adapter: The Key to Solving Industry Challenges

As an industrial-grade dual serial to Ethernet adapter, the USR-N520 is equipped with a Cortex-M7 core running at 400MHz and supports independent operation of dual serial ports. It features three major technological breakthroughs:

• Deep protocol compatibility: Supports Modbus RTU/TCP mutual conversion, allows custom message formats, and is compatible with various heterogeneous devices.
• Flexible trigger rules: Supports 8 modes including conditional triggering, timed triggering, and heartbeat triggering, with a response delay of less than 50ms.
• Convenient and efficient debugging: Provides a dual interface of AT command set + web configuration and supports remote firmware upgrades.
  (Here, you can insert a product image: The USR-N520 dual serial to Ethernet adapter features an industrial-grade design and supports operation in a wide temperature range of -40 to 85℃.)

N520

Ethernet Serial Server2*RS485MQTT+SSL

3. Guide to Implementing Custom Message Formats

3.1 Design of Message Structure Elements

Based on the AT command set of the USR-N520, a message format containing the following elements can be defined:
[Frame Header][Device Address][Command Code][Data Length][Data Field][Check Code][Frame Tail]
Example: When connecting a temperature sensor, design the following format:
0xAA 0x01 0x03 0x02 0x00 0x1A 0x55 0xBB

• Frame Header: 0xAA (fixed identifier)
• Device Address: 0x01 (sensor number)
• Command Code: 0x03 (read temperature command)
• Data Length: 0x02 (2-byte data)
• Data Field: 0x00 0x1A (temperature value of 26℃)
• Check Code: 0x55 (CRC16 check)
• Frame Tail: 0xBB (end identifier)

3.2 AT Command Configuration Process

Send the following commands through a serial debugging tool to complete the configuration:

3.3 Practical Application Scenario

In a smart agriculture project, the linkage between a soil moisture sensor and an irrigation system is achieved through custom messages:
[0xAA][0x02][0x04][0x01][0x32][0x55][0xBB]
When the data field value 0x32 (50% humidity) is below the threshold, the system automatically triggers an irrigation command.

4. Advanced Configuration Methods for Trigger Rules

4.1 Conditional Trigger Mode

Set data thresholds to trigger alarms through AT commands:

Application case: A cold chain logistics enterprise achieved real-time monitoring of drug transportation temperatures through this mode, increasing the alarm accuracy rate to 99.2%.

4.2 Timed Trigger Mode

Set data collection and reporting every 5 minutes:

Advantage: Compared to traditional polling mode, network bandwidth usage is reduced by 75%.

4.3 Heartbeat Trigger Mode

Maintain device online status detection:

Technical principle: If no heartbeat packet is received within 60 seconds, the system automatically marks the device as offline and sends an alert.

5. Practical Tips for Debugging and Optimization

5.1 Three-Step Quick Diagnosis Method

• Basic connectivity test: Send an AT command and confirm normal communication by receiving an "OK" response.
• Parameter consistency check: Query the current configuration through AT+PARAM? to ensure it matches the device requirements.
• Data flow monitoring: Use AT+LOG=1 to enable debugging logs and track data flow in real time.

5.2 Batch Configuration Script Example

Achieve batch configuration of parameters for 20 devices through a Python script:

5.3 Performance Optimization Suggestions

• Baud rate matching: Choose 115200bps (default) or 230400bps according to the data volume.
• Data framing processing: It is recommended to split data exceeding 128 bytes for transmission.
• Watchdog mechanism: Enable AT+WDT=1 to prevent device crashes.

6. Industry Solution Case Library

6.1 Smart Factory Device Networking Solution

An automobile manufacturing enterprise achieved the following through the USR-N520:

• Seamless connection between 300 PLCs (Modbus RTU) and the MES system.
• Custom message formats compatible with devices from 6 brands.
• Trigger rules enabling the location of faulty devices within 30 seconds.

6.2 Environmental Monitoring System Solution

After adopting this solution, an environmental monitoring station achieved the following:

• Reduced the data reporting delay of air quality sensors from 15 seconds to 2 seconds.
• Supported the simultaneous connection of 8 types of sensors including GPS, temperature, and humidity.
• Reduced annual operational and maintenance costs by 60%.

7. Contact Us: One-on-One Communication with PUSR Experts

• Requirement : Clearly define key parameters such as device type, communication protocol, and trigger conditions.
• Solution customization: Contact the technical team to obtain the "USR-N520 Industry Solution White Paper".

Usher in a New Era of Intelligent Connectivity

Through in-depth customization using the AT command set, the USR-N520 upgrades traditional serial to Ethernet adapters into programmable intelligent communication hubs. According to actual test data from a customer, after adopting this solution, the system integration cycle was shortened by 40%, and data transmission stability was increased to 99.97%. In the wave of Industry 4.0, this flexibility will become the core competitiveness for enterprises' digital transformation. Consult now to obtain your customized solution!