As a senior engineer at  yeaplink, I have spent considerable time researching and implementing RS232 connections between industrial routers and various devices. This article summarizes my original insights and practical experiences in this field.The process of connecting an industrial router to other devices using RS232 can be divided into two main parts:

hardware connection and software configuration.Hardware Connection:

1. Interface Identification: The first step is to locate the RS232 interface on the industrial router. Typically, this is a 9-pin DB9 female connector. In our products, we clearly label it as “RS232” for easy identification.
2. Cable Selection: Choosing the right RS232 cable is crucial. We recommend using shielded twisted pair cables to reduce electromagnetic interference. The cable length should be kept under 15 meters, as RS232 signals degrade significantly over longer distances.
3. Pin Connection: The main pins used in RS232 are TXD (Transmit Data), RXD (Receive Data), and GND (Signal Ground). When connecting, the router’s TXD should be connected to the device’s RXD, the router’s RXD to the device’s TXD, and ensure the GND is connected. This cross-connection ensures correct data transmission.
4. Signal Levels: RS232 uses negative logic levels, where -3V to -15V represents logic “1”, and +3V to +15V represents logic “0”. Our routers have built-in level conversion circuits, converting TTL levels to RS232 levels internally.
5. Protection Measures: Considering the complexity of industrial environments, we’ve incorporated overvoltage and ESD protection in our RS232 interface circuits. These measures effectively prevent damage from static discharge and transient overvoltage.

Software Configuration:

1. Serial Port Parameter Settings: Through the router’s web management interface, we can configure RS232 interface parameters, including:
   • Baud rate: Common options are 9600, 19200, 38400, 57600, 115200 bps.
   • Data bits: Usually 8 bits.
   • Stop bits: Can be 1 or 2 bits, commonly 1 bit.
   • Parity: Options include none, odd, or even.
   • Flow control: Option to enable hardware flow control (RTS/CTS).
2. Working Mode Selection: Our routers support multiple RS232 working modes:
   • Transparent transmission mode: Directly forwards RS232 data to network ports.
   • Modbus gateway mode: Converts RS232 Modbus RTU data to Modbus TCP.
   • Custom protocol mode: Allows customized data processing logic based on client needs.
3. Data Packaging: In transparent transmission mode, we need to set data packaging parameters such as package length and packaging interval time. These parameters determine how the router encapsulates serial data into network packets.
4. Serial Port Debugging: We’ve integrated a serial port debugging tool in the router, allowing direct viewing of serial data through the web interface, greatly facilitating the debugging process.
5. Data Forwarding Rules: Configure rules for forwarding RS232 data, such as forwarding to specific IP addresses and ports, or to other interfaces of the router (e.g., 4G, Ethernet).
6. Security Settings: Considering the sensitivity of industrial data, we’ve implemented an IP-based access control list, allowing only authorized clients to access serial port data.

In practical applications, I encountered an interesting case where a client needed to integrate an old industrial controller with RS232 interface into a modern network monitoring system. We connected the controller to our industrial router via the RS232 interface, then uploaded the data in real-time to a cloud platform through a 4G network. This not only solved the networking issue for the old equipment but also enabled remote monitoring and data analysis, significantly improving factory operational efficiency.Another challenge was dealing with different device communication protocols. Sometimes, RS232 devices might use non-standard or proprietary protocols. To address this, we developed a flexible protocol parsing framework that allows users to define their own protocol parsing rules using a simple scripting language. This greatly increased the adaptability of our routers, enabling seamless integration with various specialized devices.In conclusion, connecting industrial routers to other devices via RS232 is a process that comprehensively considers hardware compatibility, software flexibility, and practical application requirements. Through careful design and configuration, our industrial routers can serve as a crucial bridge connecting traditional RS232 devices to the modern network world, providing strong support for industrial automation and digital transformation.