Hymns of praise have often been sung about IO-Link. The advantages of bidirectional digital communication compared to classic analogue and digital interfaces are now internationally recognized. Cost-effective wiring, diagnostic options, parameterization options, intelligent data storage, simplified e-planning and, last but not least, cross-manufacturer support of the standard are convincing designers, e-planners and PLC programmers. This explains the success and increasing global spread of IO-Link. The graph of installed nodes over the last ten years shows exponential growth to around 10 million devices.

However, it has not yet been mentioned that IO-Link also has its limits. In particular, the integration of IO-Link devices into Profinet systems has been a shortcoming to date.

A GSDML file (Generic Station Description Markup Language) is supplied with every Profinet device. It enables the control system programmer to schedule and parameterize the device offline in the project (usually in the TIA portal) before the project is actually connected to the network and the connected devices. These two processes initially run independently, especially in large projects.

Manufacturers of IO-Link devices do not provide them with their own GSDML file; instead, the device description is designed as an IO-Link Device Description (IODD). As a result, the Profinet configuration software cannot recognize the devices without detours. Until now, users have been forced to enter properties such as device class or manufacturer ID manually. Parameters such as measuring ranges and output signals have to be programmed or set using additional software.

IODD interpreter only suitable to a limited extent

Such additional software are interpreters of IODDs in other systems, as they are already used in various software tools. These programs can be used to make the necessary settings on the IO-Link device. The device is then integrated into the Profinet project. However, this is not a satisfactory solution, especially in large projects: PLC programmers often have to work with countless tools in order to integrate the devices of all manufacturers. Many programmers therefore have to program IO-Link devices into their control environment manually. In addition to the time required and the high know-how threshold of this solution, it is also prone to errors. The problems that maintenance engineers have with projects that have been configured with different tools are only mentioned here in passing.

Integrated in GSDML files

Turck recognized this shortcoming of IO-Link early on and worked for several years on the 'SIDI' function (Simple IO-Link Device Integration). IO-Link devices are entered as Profinet submodules in the GSDML of the IO-Link master. The company is now equipping its IO-Link masters in block module design with the SIDI function. Anyone who integrates one of these IO-Link masters into a Profinet project
can use the connected IO-Link devices as Profinet modules.
Turck integrates all of its own IO-Link devices into the SIDI library as standard, as well as the devices from Banner Engineering as a strategic partner for optical sensors. The first IO-Link devices from third-party manufacturers are also already included. Further IO-Link devices from other manufacturers are to be added to the SIDI library in the future. Every device that is to be included in the SIDI catalog is first thoroughly tested to guarantee smooth operation and user-friendliness.

Insert via drop-down

With 'SIDI', IO-Link devices can be integrated directly into Profinet configuration software such as the TIA Portal. They can be selected from the hardware catalog just like Profinet modules.

© Turck

If the connected device is in the SIDI-GSDML, the PLC programmer can select it from the device catalog in his programming environment. For these devices, he can now view all IO-Link-relevant properties and change parameters such as measuring ranges, output signals or pulse rates in the plain text field.

SIDI is particularly useful for large projects: Large systems and machines are usually initially created offline as a project. The Profinet devices are added to the device tree and are usually selected from the TIA Portal library. With SIDI, offline engineering is also possible throughout with IO-Link devices. This means that the devices do not have to be on the PLC programmer's desk, and he does not have to visit each device in advance with his laptop to make the necessary settings using a USB adapter. Consistent offline access to all device data from the desk saves a lot of time in large projects compared to IO-Link integration without SIDI.

Plug & Play device replacement

SIDI' works with different engineering systems as it is based on standard Profinet mechanisms.

© Turck

In addition to engineering, SIDI simplifies maintenance. As all device properties and parameters of masters and devices are available directly in the central project storage of the controller, automatic device replacement is easy - both for IO-Link masters and devices. Only the Profinet name needs to be set on the master; using Profinet with topology information, even this works automatically. Neither measuring ranges nor other parameters need to be set for the devices used.

Author:
Aurel Buda is Product Manager Fieldbus Systems Factory Automation at Turck in Mülheim.