RS232: what it is and how it works in industrial communication

RS232 is a serial communication standard used to exchange data between devices. It is one of the oldest and most widely used communication protocols in industrial applications and is still used in embedded systems, measurement equipment, and IoT solutions.

Within IoT and industrial environments, RS232 is often used for simple and reliable communication between devices.

Summary

RS232 is a serial communication standard that allows devices to exchange data through a direct connection.

Key points to remember:

• RS232 is a point-to-point communication protocol
• data is transmitted serially (bit by bit)
• it is used for short distances
• it is simple and reliable
• it is still used in industrial and IoT systems

What RS232 actually is

RS232 is a standard for serial communication that defines how data is electrically and logically transmitted between two devices. It is often used to connect a computer to a modem, PLC, or other industrial device.

Unlike parallel communication, where multiple bits are sent at once, RS232 transmits data one bit at a time over a single line.

This makes it simple and stable, but less suitable for high data rates.

How RS232 works

RS232 operates through a direct connection between two devices, typically referred to as DTE (Data Terminal Equipment) and DCE (Data Communication Equipment).

The basic operation:

• a device sends data via a serial port
• the data is transmitted bit by bit
• the receiving device reads the bits in the same order
• the data is interpreted and processed

Communication takes place using predefined parameters such as baud rate, parity, and stop bits.

Key characteristics of RS232

RS232 has several features that make it suitable for specific use cases.

Point-to-point communication

RS232 connects two devices directly.

Simple implementation

The protocol is easy to implement and widely supported.

Low data rate

Suitable for simple data exchange, but not for large data volumes.

Limited distance

Typically suitable for short distances (around up to 15 meters).

Benefits of RS232

Despite its age, RS232 is still used because of its advantages.

Reliability

Simple communication ensures stable connections.

Wide support

Many industrial devices support RS232.

Low complexity

No complex network configuration is required.

Suitable for embedded systems

Ideal for simple communication between devices.

RS232 in IoT and industry

Within IoT, RS232 is often used alongside modern systems.

Examples:

• communication between a PLC and a sensor
• connecting legacy systems to IoT gateways
• reading data from measurement equipment
• integrating older devices into modern networks

RS232 is often combined with gateways that translate data into IP-based protocols such as MQTT or HTTP.

RS232 vs modern protocols

RS232 differs from modern communication protocols.

RS232:

• simple point-to-point connection
• low data rate
• no networking capabilities

Modern protocols:

• operate over networks and the internet
• support multiple devices
• offer higher speed and flexibility

Despite this, RS232 remains relevant for specific applications.

Considerations when using RS232

Although RS232 is simple, there are limitations.

Distance and speed

Not suitable for long distances or high data rates.

Limited scalability

Only two devices can communicate directly.

Legacy technology

Often replaced by newer alternatives in modern systems.

Why RS232 is still used

Many industrial systems have long lifecycles. As a result, RS232 remains relevant, especially in existing installations.

It helps to:

• continue using legacy systems
• enable simple communication
• maintain reliable connections
• integrate with IoT through gateways

This makes RS232 a practical solution in specific scenarios.

RS232 vs. RS485

RS232 and Thingsdata

Thingsdata supports RS232 communication in various industrial solutions, including routers and gateways with RS232 ports, protocol conversion from RS232 to TCP/IP, MQTT, or Modbus, remote monitoring of legacy equipment via LTE-M or NB-IoT, and eSIM connectivity linked to serial equipment in the field.

Conclusion

RS232 is a simple and reliable standard for serial communication between devices. Although it is an older technology, it is still widely used in industrial and IoT applications, especially for connecting legacy systems.

For organizations working with legacy hardware and embedded devices, RS232 provides a stable foundation for communication and integration with modern IoT solutions.

For more information, please contact us by phone at +31-85-0443500 or via email at info@thingsdata.com.