IODD

Key takeaways

IODD belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect IODD to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of IODD from memory before moving on to harder problems.

Reference excerpt

The IODD (IO Device Description) describes sensors and actuators with an IO-Link communication interface. It contains information about the device’s identity, parameters, process data, diagnosis data, communication properties and the design of the user interface of engineering tools. The IODD comprises different data files: the main file and several optional language files are in XML-format and optional graphical files are in PNG-format (portable network graphics).

Structure The IODD structure conforms to the specifications of the standard ISO 15745 “Industrial automation systems and integration – Open systems application integration framework”. The IODD unifies the device profile and the communication network profile in one data file. According to the structure defined in ISO 15745, the IODD provides the objects DeviceIdentity and DeviceFunction for the device description. The DeviceIdentity object contains text with information for the user and identification numbers (IDs) to automatically identify sensors and actuators in the plant. The IODD enables the vendor to describe variants of products, which are equal in their parameters, process and diagnosis data and communication but vary in their order number. In this way it is ensured that the high diversity of the mechanical characteristics, which characterize the sensors and actuators, will not result in an unnecessary high number of device descriptions and a high consumption of identification numbers. The DeviceFunction object is the recipient of any other information if these information do not belong to the communication profile. It contains the description of the device’s parameters, process data, diagnosis data and configuration of the user interface. The embedded communication network profile can be easily replaced and hence the IODD can be easily used to describe sensors and actuators with different communication interfaces.

Language support The textual data can be specified in multiple languages. In the actual device description only text identifiers are used. Separate text lists (for each supported language one is necessary) link the corresponding language-dependent text to the text identifier. Usually all of the text lists are included in the main file. For subsequent translation into other languages the text lists can be provided as separate files to leave the main file unchanged.

Standard definition All parameters and diagnosis data, pre-defined by the IO-Link standard, are described in the file"IODD-StandardDefinitions[version].xml" with the same syntax used in the IODD. These default parameters and diagnosis data are not described but referenced in the IODD. The IODD specification, the IODD guideline with examples and the IODD Checker are provided by the IO-Link Consortium. At present, the IODD version V1.0.1 is available, which describes devices based on the IO-Link specification V1.0 as well as devices based on the IO-Link specification V1.1 in V1.0 compatibility mode. In future, IODD V1.1 will provide a description of devices for the IO-Link specification V1.1. The IODD V1.1 will not replace the V1.0.1.

IODD Checker The tool "IODD Checker" considers not only the compliance of the schemas but also all the rules of the IODD specification, which can not be checked by the XML schema. After passing the examination the IODD is stamped by the Checker. This test is mandatory. Engineering tools only accept stamped IODDs hence there is no need to implement these tests in the engineering tool.

IODD Finder The IO-Link community provides interfaces to an "IODD Finder", which can be used by engineering or master tools to present the appropriate IODD for a device.

Worked examples

Example 1 — a first encounter with IODD

Start with the simplest possible case. Write down what IODD claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to IODD before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about IODD ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of IODD

In research: IODD appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses IODD in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: IODD is common in secondary-school and first-year university syllabi. It links to neighbouring topics Computer file formats, Industrial automation, so understanding it makes those chapters shorter.
In everyday life: Look for IODD outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study IODD in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what IODD means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain IODD out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is IODD in simple terms?

The IODD (IO Device Description) describes sensors and actuators with an IO-Link communication interface. It contains information about the device’s identity, parameters, process data, diagnosis data, communication properties and the design of the user interface of engineering tools.

Why does IODD matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study IODD?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on IODD.