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CODESYS supports serial communication with different methods depending on the device configuration:

  • COM port via function library:
    The free Serial_Communication library is supplied with the CODESYS Development System. This library is used for the simple administration of COM ports (RS232 / RS 422 / RS485) as well as the reading/writing of data from the controller application.
  • Modbus Serial (RTU) via own configurator:
    You can simply use the COM port of a CODESYS-compatible controller for Modbus communication (master/slave). For this purpose, use the seamlessly integrated Modbus configurator. If the controller does not come with the required license, this license can be obtained from the CODESYS Store subsequently.
  • SPI / I²C / 1-Wire® via runtime system component:
    Especially on standard device platforms, users can expand the available memory or functionality by means of serial data buses or communication interfaces. CODESYS supports SPI (Serial Peripheral Interface), I²C (Inter-Integrated Circuit), as well as 1-Wire thanks to components of the CODESYS Control Runtime System that can be integrated into the CODESYS Development System via corresponding drivers.
  • Own serial protocols:
    If your device has a low-level device driver that you can address in the application, you can develop your own serial communication protocols using the programming functionalities of a modern programming tool (IDE).
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How can you purchase and use the communication options via serial interfaces integrated in CODESYS?

How can you purchase and use the communication options via serial interfaces integrated in CODESYS?

  • You are a system integrator or a user in the machine/plant construction sector or the like:
    • Use CODESYS-compatible controllers or standard device platforms that are equipped with integrated serial interfaces.
    • Download the adequate CODESYS Control SoftPLC system from the CODESYS Store that already includes a number of protocols and install it on the standard device platforms.
    • In application development, use the Serial_Communication library that is included free of charge in the scope of delivery.
    • Use device platforms that can be extended with SPI, I²C or 1-Wire using the suitable CODESYS Control runtime system.
    • Or you can develop your own protocol libraries, which you can offer to other users in the CODESYS Store. Have experienced specialists advise and support you in architectural design and implementation. Further information is available at https://www.codesys.com/products/codesys-services/user-services.html.
  • You are a manufacturer of programmable devices:
    • Implement the required communication components of the CODESYS Runtime Toolkit in your devices, as well as the possibility to license libraries per device.


CODESYS offers seamlessly integrated communication protocols for a wide variety of interfaces and requirements.

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OPC Server

Standard Interface to access the IEC 61131-3 process data of a controller via Open Platform Communications.

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Standard Interface for Communication in Smart Factory and Industry 4.0 Systems

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Compact software interface (API) for easy access to the PLC variables in CODESYS controllers from external systems

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Configurator and protocol stack fully integrated in the IEC 61131-3 Development System

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Standard Ethernet

How does CODESYS communicate via Ethernet? How can I send and receive data from a CODESYS-compatible PLC via TCP or UDP? How can I realize data exchange from the PLC application?

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Fieldbus systems and Industrial Ethernet

Sensors and actuators/actuators for processing control tasks can be separated from the controller via fieldbus and Ethernet systems with industrial communication protocols.

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IIoT libraries

All IoT communication protocols can be implemented and used on different transmission media via software.

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Other communication options

If a physical port is available on a controller, communication protocols can usually be implemented simply via software, either as part of the IEC 61131-3 control application or as separate library modules. Data exchange is performed by explicitly calling functions or function blocks as part of the logic control.

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Proprietary communication protocols

CODESYS supports the most common standard communication protocols for data exchange between controllers, such as OPC UA. In addition, Ethernet-based fieldbus systems such as PROFINET or EtherNet/IP™ make it easy to exchange data between controllers by implementing master and slave functions.

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