ESI File / EtherCAT SubDevice Information

ESI files (EtherCAT SubDevice Information) play a crucial role in industrial automation and communication via the EtherCAT protocol (Ethernet for Control Automation Technology). EtherCAT is a high-performance, industrial real-time Ethernet protocol that is widely used in automation applications due to its high communication speeds and deterministic behavior. 

The primary purpose of ESI files is to provide comprehensive information about EtherCAT SubDevices to the MainDevice device. This includes details about the SubDevice's capabilities, supported features, and communication parameters. The ESI file allows the EtherCAT MainDevice to automatically configure the SubDevice during network startup. They serve as a standardized means for EtherCAT MainDevices (such as PLCs or industrial PCs) to understand and communicate effectively with EtherCAT SubDevices (such as sensors, actuators, drives, or other control devices) on the network. 

They are XML-based and follow a standardized format defined by the EtherCAT Technology Group (ETG). The structure of an ESI file is specified in the EtherCATInfo.xsd XML schema document. This ensures a consistent format across all ESI files, allowing for seamless integration and configuration of EtherCAT networks. 

The information contained in the ESI file enables the EtherCAT MainDevice to automatically configure the SubDevice during network startup. This includes mapping process data objects (PDOs) and setting up service data object (SDO) initialization sequences. Ensuring the ESI file matches the firmware version of the SubDevice is crucial for seamless communication and functionality. 

ESI files can be edited using text editors or graphical XML editors. Some types of EtherCAT MainDevice software, such as TwinCAT, also provide built-in tools for editing ESI files. Manually editing the ESI file may be necessary when the MainDevice does not provide SDO initialization sequence support. 

The EtherCAT SubDevice Information (ESI) files used in industrial automation and communication can be categorized into two main types: Flats and Slots. 

Flats 

Flats are the standard type of ESI files. They contain information about the standard process data objects (PDOs) supported by the EtherCAT SubDevice. 

They provide a fixed, non-modular structure for the SubDevice’s PDOs. The PDOs are predefined and cannot be changed or extended by the user. The SubDevice's functionality is fixed and cannot be reconfigured. Flats are the simplest and most common type of ESI files, suitable for basic EtherCAT SubDevices. This type of ESI file is simpler and easier to understand, especially for devices with relatively few parameters or straightforward configurations. Flat ESI files are suitable for EtherCAT SubDevices that do not require complex configuration or have a limited number of configurable parameters. 

Slots 

Slot-based ESI files are more advanced and flexible compared to Flats. They support the Modular Device Protocol (MDP) defined by the EtherCAT Technology Group (ETG). 

They allow the EtherCAT SubDevice to have a modular structure, with different operational modes or "modules". Each module can have its own set of PDOs, allowing the SubDevice’s functionality to be reconfigured. The modules can be of different types, such as Cyclic Synchronous Position (CSP), Cyclic Synchronous Velocity (CSV), and Cyclic Synchronous Torque (CST). The EtherCAT MainDevice can dynamically select and activate the appropriate module based on the application requirements.  

Slot-based ESI files provide more flexibility and customization options for complex EtherCAT SubDevices. They allow for more detailed and structured representation of device configuration, making them suitable for complex EtherCAT SubDevices with extensive PDO mapping requirements or synchronization features. They provide a more granular view of the device's capabilities and configuration options, enabling EtherCAT MainDevices to configure and communicate with the SubDevice more efficiently. 

Flat ESI files offer a simple and straightforward representation of EtherCAT SubDevice information, while Slot-based ESI files provide a more structured and detailed view, particularly suitable for complex devices with extensive PDO mapping requirements. The choice between Flat and Slot-based ESI files depends on the complexity of the EtherCAT SubDevice and the level of detail required for configuration and communication within the EtherCAT network. 

The technical features of ESI (EtherCAT SubDevice Information) files are designed to provide comprehensive documentation and configuration capabilities for EtherCAT SubDevices within an EtherCAT network. 

Device identification

ESI files contain information about EtherCAT SubDevices, including their vendor name, product ID, revision number, and device type. This allows EtherCAT MainDevices to identify and differentiate between connected SubDevices on the network. 

Parameter definitions

ESI files define the parameters, variables, and data objects accessible on EtherCAT SubDevices. They specify the data types, sizes, access rights, and addressing information for each parameter within the device's object dictionary. This enables EtherCAT MainDevices to read from and write to specific parameters during runtime. 

Communication profiles

They specify the communication profiles supported by EtherCAT SubDevices. This includes the data exchange formats, cyclic data transfer rates, synchronization methods, and other communication parameters necessary for seamless interaction within the EtherCAT network. 

PDO mapping

ESI files describe the Process Data Object (PDO) mapping of EtherCAT SubDevices. PDO mapping defines how input and output data is structured and exchanged between the EtherCAT MainDevice and SubDevices. ESI files specify the layout of PDOs, including the mapping of process data, status information, and configuration data. 

Synchronization features

For devices requiring synchronized operation, ESI files detail the synchronization features supported by EtherCAT SubDevices. This includes distributed clock synchronization, timestamping, and other mechanisms to ensure precise timing and coordination among devices within the EtherCAT network. 

Configuration parameters

ESI files contain configuration parameters that determine the behavior and operation of EtherCAT SubDevices. These parameters may include network settings, communication parameters, device-specific features, and other configurable options. 

Vendor neutrality

It adheres to standardized formats defined by the EtherCAT Technology Group (ETG), ensuring interoperability among devices from different manufacturers. This vendor neutrality allows EtherCAT MainDevices to work seamlessly with EtherCAT SubDevices from various vendors, facilitating flexible system integration. 

Versioning and compatibility

ESI files may include versioning information to indicate compatibility with specific versions of the EtherCAT specification or EtherCAT MainDevices. This ensures compatibility and consistency across different versions of ESI files and EtherCAT implementations. 

ESI files provide essential documentation and configuration information for EtherCAT SubDevices, enabling EtherCAT MainDevices to configure, communicate with, and coordinate the operation of devices within an EtherCAT network effectively. 

The German high-tech company Hilscher is an active member of the EtherCAT Technology Group (ETG), which is responsible for defining and maintaining the ESI file specification.  

Hilscher offers a range of industrial communication solutions that support companies in automating their systems. These include the netX communication controllers developed in-house as well as PC cards, embedded modules, gateways, switches and IIoT solutions based on them. 

Thanks to its innovative, multi-protocol-capable solutions, Hilscher is one of the technology leaders in the field of industrial communication.