Notes regarding ESI device description

Installation of the latest ESI device description

The TwinCAT EtherCAT master/System Manager needs the device description files for the devices to be used in order to create the configuration in online or offline mode. The device descriptions are contained in the so-called ESI files (EtherCAT Slave Information) in XML format. These files can be requested from the respective vendor and are made available for download. An *.xml file may contain several device descriptions.

The ESIs for Beckhoff EtherCAT devices are provided on the Beckhoff website.

The ESI files must be stored in the TwinCAT installation directory.

Default settings:

TwinCAT 3: C:\TwinCAT\3.1\Config\Io\EtherCAT

The files are read (once) when a new System Manager window is opened, if they have changed since the last time the System Manager window was opened.

A TwinCAT installation includes the set of Beckhoff ESI files that was current at the time when the TwinCAT build was created.

From TwinCAT 3 on the ESI directory can be updated from the System Manager if the programming PC is connected to the internet; at

TwinCAT 3: TwinCAT → EtherCAT Devices → “Update Device Descriptions (via ETG Website)…”

The TwinCAT ESI Updater is available for this purpose.

	ESI The .xml files are associated with .xsd files, which describe the structure of the ESI XML files. To update the ESI device descriptions, both file types should therefore be updated.

Device differentiation

EtherCAT devices/slaves are differentiated by four properties, from which the complete device designation is composed. For example, the device designation "EL2521-0025-1018" consists of:

family key “EL”
name "2521"
type "0025"
and revision “1018”

Notes regarding ESI device description 2: — Device designation: Structure

The order identifier consisting of name + version (here: EL2521-0010) describes the device function. The revision indicates the technical progress and is managed by Beckhoff. In principle, a device with a higher revision can replace a device with a lower revision, unless specified otherwise, e.g. in the documentation. Each revision has its own ESI description. See further notes.

Faulty ESI file

If there is a faulty ESI file that cannot be read by the System Manager, the System Manager displays an information window.

Notes regarding ESI device description 3: — Information window faulty ESI file (TwinCAT 3)

This can be caused by

Structure of the *.xml does not correspond to the associated *.xsd file → check your schematics
Contents cannot be compiled into a device description → contact the file manufacturer

Online description

If the EtherCAT configuration is created online by scanning real existing devices (see chapter Online creation) and there is no ESI description available for a slave found (identified by name and revision), the System Manager asks whether it should use the description available in the device. The System Manager always requires this information in order to set the cyclical and acyclical communication with the slave correctly.

A window appears in TwinCAT 3 that also offers the web update:

Notes regarding ESI device description 4: — OnlineDescription information window (TwinCAT 3)

If possible, the Yes is to be rejected and the required ESI is to be requested from the device vendor. After installation of the XML/XSD file the configuration process should be repeated.

Notice

Changing the ‘usual’ configuration through a scan

in the case of a device detected by a scan but still unknown to TwinCAT, two cases must be distinguished. Taking the example here of the EL2521-0000 in the revision 1019:

no ESI is present for the EL2521-0000 device at all, either for the revision 1019 or for an older revision. The ESI must then be requested from the vendor (in this case Beckhoff).
for the EL2521-0000 device, an ESI is only available in an older revision, e.g. 1018 or 1017.
In this case, you should first check internally whether the spare parts inventory allows the higher revision to be integrated into the configuration. A new/larger revision usually also brings new features. If these are not to be used, work can continue without reservations with the previous revision 1018 in the configuration. This is also stated by the Beckhoff compatibility rule.

Refer in particular to the chapter "General notes on the use of Beckhoff EtherCAT I/O components" and for manual configuration to the chapter "Offline configuration creation".

If the online description is nevertheless used, the System Manager reads a copy of the device description from the EEPROM in the EtherCAT slave. In complex slaves the size of the EEPROM may not be sufficient for the complete ESI, in which case the ESI would be incomplete in the configurator. For this reason, the use of an offline ESI file is recommended as a matter of priority.

The System Manager creates a new file "OnlineDescription0000...xml" in its ESI directory for device descriptions recorded "online", which contains all ESI descriptions read online.

Notes regarding ESI device description 5: — Created by the System Manager OnlineDescription.xml

If a slave is then to be added manually to the configuration, slaves created "online" are identified by a preceding ">" symbol in the selection list (see figure Identification of an ESI recorded online using the EL2521 as an example).

Notes regarding ESI device description 6: — Identification of an ESI recorded online using the EL2521 as an example

If such ESI files are used and the vendor's files become available later, the file OnlineDescription....xml should be deleted as follows:

close all System Manager windows
restart TwinCAT in Config mode
delete "OnlineDescription0000...xml"
open TwinCAT System Manager again

This file must then no longer be visible, update folder with <F5> if necessary.

	OnlineDescription under TwinCAT 3.x In addition to the "OnlineDescription0000...xml" file mentioned above, TwinCAT 3.x also creates a so-called EtherCAT cache with newly discovered devices, e.g. under Windows 7 at (note the language settings of the operating system!) This file must be deleted at the same time as the other file.