In the context of the Web of Things (WoT), a Binding Template is a blueprint that gives guidance on how to implement a specific IoT protocol, data format or IoT platform. The Core Binding Templates specification explains the overall mechanism and requirements for any binding to follow. This document gives implementation guidelines regarding the PROFINET protocol, which is a well-known high-speed industrial ethernet protocol for communication between industrial control and automation devices.
More specifically, this document defines a set of vocabulary terms that can be used inside a Thing Description [[WOT-THING-DESCRIPTION]] (TD)document, and associated rules which allow to describe WoT operations using the PROFINET protocol over the network. Additionally, relevant examples are provided to showcase different vocabulary terms and the associated behavior.
This document is a work in progress
PROFINET is an open standard communication protocol developed and published by PROFIBUS Nutzerorganisation (PNO) for Industrial Ethernet. PROFINET which is an Ethernet version of PROFIBUS is designed to satisfy requirements of most industrial automation processes by providing a high-speed data transfer for time critical applications like motion control and drive. It can also have a safety (PROFIsafe) implementation onboard for safety related application.
Generally, profinet is classified into PROFINET IO (Input Output) which is used for distributed input/output processes of field devices (sensors and actuators) data and PROFINET CBA (Component Based Automation) which is used for distributed automation. The scope of this document focuses on the PROFINET IO. PROFINET IO network consist of three main actors which are IO controller, IO supervisor and IO device. The IO controllers are PLCs and DCS, they are most used for profinet cyclic communications like IO data exchange. The IO supervisor is a standalone application that is mostly used for acyclic communications like diagnostics and parameterization. The IO device is general field devices that are controlled by both IO controller and IO supervisor [[IEC CD 61158-5-10]].
Due to the different requirements by different industrial automation applications, PROFINET IO provides three different communications channels to exchange data between IO controllers and IO device or IO supervisor and IO devices. The Real-Time (RT) and Isochronous Real Time (IRT) channels are used for cyclic data transfer and high-speed cyclic data transfer for motion control application respectively, the Non-Real-Time channel which is based on User Data Protocol (UDP) is mostly used by IO supervisor for parameterization, diagnostic and acyclic communications. The RT channel can also be used for acyclic real time messages like alarm The addressing in PROFINET slot/sublsot/index mechanism where the slot identifies a module and subslot identifies submodules that exist within a module. The index identifies datapoint of interest in the submodule [[IEC CD 61158-5-10]].
Concretely, this document describes how WoT TDs can be used to describe devices that use the PROFINET acyclic non-real time communication (IO supervisor) [[Profinet Uni]]. The IO controller operations that use cyclic communication is beyond the scope of this document. This document explains how to create valid URLs and Forms for read or write operation from or to an IO device respectively. Developers are encouraged to use this document as an implementation guideline and as a reference for the creation of their own binding implementations. The following sections will cover the URL format, the vocabulary and a list of Form examples.
A Thing Description instance with PROFINET Binding complies with this specification if it follows the normative statements in and .
A JSON Schema [[?JSON-SCHEMA]] to validate Thing Description instances containing PROFINET Binding is provided in the GitHub repository.
In conformance with the structure of other bindings provided in the WoT TD, the URL form defines a resource
endpoint's information, and it
follows a standard URL scheme common to the web. For PROFINET, the URL scheme will begin with
profinet:// and that will be
the only valid scheme to consider.
The following shows the typical structure of an URL of the PROFINET protocol:
profinet://{address}/{slot}/{subslot}/?api={api}&index={index}&datalength={datalength}
Where:
{address} is the IP address of the PROFINET IO device{slot} is the module where the PROFINET IO module is plugged into. See vocabulary{subslot} is the is the logical submodule where the PROFINET IO device parameter is
located. See vocabulary{api} known as Application Process Identifier, for distinguishing profiles parameter. See
vocabulary{index} identifies a parameter within slot/subslot address. See vocabulary{datalength} defines the length of byte resource payload is expected to be. See vocabularyThis section describes the vocabulary used in the PROFINET protocol. An implementation of a protocol binding template should use the vocabulary defined in this section to describe the different configurations that Things can use to exchange data on the Web of Things.
| Vocabulary term | Description | Assignment | Type |
|---|---|---|---|
profv:slot |
Specifies the location where the IO device is plugged in to. | required | integer |
profv:subslot |
Provides the interface for the parameter to read/write. A slot can contain one or more subslots | required | integer |
profv:index |
An identifier that uniquely points to a resource within slot/subslot combination of a PROFINET IO device | required | integer |
profv:api |
Used to provide additional addressing to differentiate profile parameters. If the term is
not provided, the TD processor treats it as the default of zero. |
optional | integer |
profv:datalength |
used in application and network optimization to appropriately define the specific data length of resource payload. | optional | integer |
| Vocabulary term | Description | Assignment | Type |
|---|---|---|---|
profv:mostSignificantByte |
When true, it indicates that the byte order of the data in the PROFINET message
is most-significant byte (i.e., Big-Endian). When false, it indicates
least-significant-byte (i.e., Little-Endian).If the term is not provided, the TD processor
defaults it to true |
optional | boolean |
profv:mostSignificantWord |
When true, it indicates that the word order of the data in the PROFINET message
is most-significant-word (i.e., no word swapping). When false, it indicates
least-significant-word (i.e., word swapping). If the term is not provided, the TD processor
treats it as the default of true. |
optional | boolean |
profv:method |
Indicates operation to perform on defined affordance. | string
(one of "READ", "WRITE") |
|
profv:pollingTime |
IO supervisor polling rate in milliseconds. To ensure that the cyclic communication will not be interrupted, it is recommended to keep this polling rate above the IO device's send clock time. | optional | integer |
profv:timeout |
PROFINET response maximum waiting time. Defines how long the runtime should wait to receive a reply from the device. | optional | integer |
profv:byteOffset |
For object type properties. Used to identify the starting point within a byte
stream payload that represents a property. |
optional | integer |
profv:byteLength |
For object type properties. Used to identify the byte length of a property from
the byte stream payload |
optional | integer |
profv:bitOffset |
For object type properties. Used to identify the starting point within a bit
stream payload that represents a property. |
optional | integer |
profv:bitlength |
For object type properties. Used to identify the bit length of a property from
the bit stream payload |
optional | integer |
profv:payloadMapping |
used for object to provides logical mapping information of a complex payload
from a PROFINET device |
optional | Map of PayloadMapping |
profv:type |
Specifies the data type contained in the request or response payload. | optional | PayloadDataType |
The profv:mostSignificantByte and profv:mostSignificantWord properties within
the PROFINET
binding template define the byte and word order of data within a PROFINET payload. In PROFINET
communications, the arrangement of bytes and words can vary between systems, and these properties
provide a declarative way to capture such configurations.
For instance, in Big-Endian byte order (e.g., AABBCC), the most significant byte comes
first, and setting profv:mostSignificantByte to true ensures the correct
interpretation of the data as AABBCC. Conversely, in Little-Endian byte order (e.g.,
CCBBAA), the least significant
byte comes first; therefore. profv:mostSignificantByte has to be set to false.
Similarly, the profv:mostSignificantWord property extends this functionality to message
payloads
composed by more than two bytes. For example, given a message payload composed by four bytess (e.g.,
AABBCCDD),
with profv:mostSignificantWord set to true, the client will interpret the data
as AABBCCDD,
while setting the property to false will result in the client interpreting the data as
CCDDAABB.
Although almost all implementations provided by vendors are Big-Endian, the PROFINET specification does
not specify Big-Endianness.
This means that some off-the-shelf or user-specific implementations might adopt Little-Endianness.
Therefore, when creating a Thing Description (TD), users are advised to account for such potential
deviations by setting the
profv:mostSignificantWord and profv:mostSignificantByte properties
accordingly.
The PayloadDataType class within the PROFINET Binding Template defines values for the
profv:type property, which is used to specify
the expected data types of payload content in PROFINET messages. It offers a set of terms taken from the
PROFINET specification (chapter 5 of IEC 61158-5-10)[ref] to
cover the most common data types used in PROFINET messages. Note that the PayloadDataType
entity is designed to describe established conventions in the PROFINET ecosystem; further development
might remove this
functionality or add new terms.
Currently, the PayloadDataType class includes the following data types[[IEC CD
61158-6-10]]:
| Value | Byte Length | Code | JSON Type |
|---|---|---|---|
| Boolean | 1 | 1 | Boolean |
| Integer8 | 1 | 2 | Integer or Number |
| Integer16 | 2 | 3 | Integer or Number |
| Integer32 | 4 | 4 | Integer or Number |
| Unsigned8 | 1 | 5 | Integer or Number |
| Unsigned16 | 2 | 6 | Integer or Number |
| Unsigned32 | 4 | 7 | Integer or Number |
| Unsigned64 | 8 | 56 | Integer or Number |
| Float32 | 4 | 8 | Number |
| Float64 | 8 | 15 | Number |
| VisibleString | profv:datalength | 9 | String |
| OctetString | profv:datalength | 10 | String |
| UnicodeString8 | profv:datalegth | 40 | String |
| 61131_STRING | profv:datalegth | 41 | String |
| 61131_WSTRING | profv:datalegth | 42 | String |
| TimeStamp | 12 | 60 | String |
| TimeStampDifference | 12 | 61 | String |
| TimeStampDifferenceShort | 8 | 62 | Integer |
| Unsigned8+Unsigned8 | 2 | 102 | Integer or Number |
| Float32+Unsigned8 | 5 | 101 | Integer or Number |
| OctetString2+Unsigned8 | 3 | 103 | String |
| Unsigned8_S | 1 | 106 | Integer or Number |
| Unsigned16_S | 2 | 104 | Integer or Number |
| Integer16_S | 2 | 105 | Integer or Number |
| OctetString_S | profv:datalegth | 107 | String |
| N2 | 2 | 113 | Integer or Number |
| N4 | 4 | 114 | Integer or Number |
| V2 | 2 | 115 | Object |
| L2 | 2 | 116 | Object |
| R2 | 2 | 117 | Integer or Number |
| T2 | 2 | 118 | Integer or Number |
| T4 | 4 | 119 | Integer or Number |
| D2 | 2 | 120 | Integer or Number |
| E2 | 2 | 121 | Integer or Number |
| C4 | 4 | 122 | Integer or Number |
| X2 | 2 | 123 | Integer or Number |
| X4 | 4 | 124 | Integer or Number |
| Unipolat2.16 | 2 | 125 | Integer or Number |
| Float64 | 8 | 15 | Integer or Number |
The payloadMapping class within the PROFINET binding template helps map the nested
properties of object types.
It is common that the payload of a PROFINET device response is provided in a complex/object form. This
payload requires mapping the individual parameters to object definitions provided by the Thing
Description dataSchema class.
The table below shows the terms provided by the payloadMapping class.
| Vocabulary term | Description | Assignment | Type |
|---|---|---|---|
profv:byteOffset |
For object type properties. Used to identify the starting point within a byte
stream payload that represents a property. |
optional | integer |
profv:byteLength |
For object type properties. Used to identify the byte length of a property from
the byte stream payload |
optional | integer |
profv:bitOffset |
For object type properties. Used to identify the starting point within a bit
stream payload that represents a property. |
optional | integer |
profv:bitlength |
For object type properties. Used to identify the bit length of a property from
the bit stream payload |
optional | integer |
profv:enumeratedValue |
used for object type properties to identify the bit mask of a proterty from the
byte stream or byte payload |
optional | Arrayof EnumeratedValue |
profv:type |
Specifies the data type contained in the request or response payload. | optional | PayloadDataType |
The enumeratedValue class within the PROFINET binding template helps provide context to encoded parameters in the payload. Bit payloads in PROFINET are sometimes used as encoded payload to logical mean something aside from 1 and 0. Information about how the encoding payload will be decoded is defined in this section. The table below defines the terms used in the enumeratedValue class.
| Vocabulary term | Description | Assignment | Type |
|---|---|---|---|
profv:encodedPayload |
used for object type properties to identify the bit mask of a proterty from the
byte stream or byte payload |
optional | number or boolean |
profv:decodedPayload |
used for object type properties to identify the bit mask of a proterty from the
byte stream or byte payload |
optional | string , number or boolean |
This section describes strategies and default values to employ protocol specific concepts within the WoT Interaction model.
The following table lists the default mappings between the protocol specific concepts and the WoT
concepts. Please note that operations that are not
listed in the table are not supported by this binding template. For example, since the scope of this
binding focuses on acyclic communication of the PROFINET protocol, the
subscribeevent operation is not supported.
| Operation | Default Binding |
|---|---|
readproperty |
"profv:method": "READ" |
writeproperty |
"profv:method": "WRITE" |
readallproperties |
"profv:method": "READ" |
writeallproperties |
"profv:method": "WRITE" |
readmultipleproperties |
"profv:method": "READ" |
writemultipleproperties |
"profv:method": "WRITE" |
| Operation | Default | Comments |
|---|---|---|
profv:api |
0
|
|
profv:mostSignificantByte |
true
|
|
profv:mostSignificantWord |
true
|
|
profv:timeout |
infinite
|
{
"@context": [
"https://www.w3.org/2019/wot/td/v1",
{
"profv": "https://profinet_vocabulary_context"
}
],
"@type": "tm:ThingModel",
"title": "ET200SP",
"id": "{{ID}}",
"profv:deviceId": 12,
"profv:vendorId": 268,
"base": "profinet://192.168.0.100",
"securityDefinitions": {
"nosec_sc": {
"scheme": "nosec"
}
},
"security": "nosec_sc",
"properties": {},
"actions": {},
"events": {}
}
[[[#example-device-property]]] shows the minimal set of terms to read or write to a PROFINET device.
Notice that the slot, subslot is contained in the href as the first and second elements of the URL path
respectively.
Also, as part of the PROFINET vocabulary is a polling mechanism (profv:pollingTime) can be used to
set intervals
for reading a PROFINET device parameter.
{
"@context": [
"https://www.w3.org/2019/wot/td/v1",
{
"profv": "https://profinet_vocabulary_context"
}
],
"@type": "tm:ThingModel",
"title": "ET200SP",
"id": "{{ID}}",
"profv:deviceId": 12,
"profv:vendorId": 268,
"securityDefinitions": {
"nosec_sc": {
"scheme": "nosec"
}
},
"security": "nosec_sc",
"properties": {
"Buffer time": {
"title": "Buffer time",
"type": "integer",
"minimum": 1,
"maximum": 60000,
"default": 3000,
"unit": "s",
"forms": [
{
"op": [
"writeproperty",
"readproperty"
],
"href": "profinet://127.0.0.1/0/1?api=0&index=268&datalength=2",
"contentType": "application/octet-stream",
"profv:type": "Unsigned16",
"profv:pollingTime": 200
}
]
}
}
}
[[[#example-complex-datatype]]] shows how object type property is defined in TM form and its mappings.
It also show how bit payload encodings and decodings are defined as enumeration.
{
"@context": [
"https://www.w3.org/2019/wot/td/v1",
{
"profv": "https://profinet_vocabulary_context"
}
],
"@type": "tm:ThingModel",
"title": "ET200SP",
"id": "{{ID}}",
"profv:deviceId": 12,
"profv:vendorId": 268,
"securityDefinitions": {
"nosec_sc": {
"scheme": "nosec"
}
},
"security": "nosec_sc",
"properties": {
"Buffering parameters": {
"title": "Buffering parameters",
"type": "object",
"properties": {
"Buffer time": {
"type": "integer",
"unit": "s",
"minimum": 1,
"maximum": 32767,
"default": 600
},
"Buffer time 2": {
"type": "integer",
"unit": "s",
"minimum": 1,
"maximum": 300,
"default": 60
},
"Buffer threshold voltage": {
"type": "integer",
"unit": "V",
"minimum": 2100,
"maximum": 2500,
"default": 2150
},
"Stop buffering threshold voltage": {
"type": "integer",
"minimum": 1800,
"maximum": 2300,
"default": 1850
},
"Input voltage OK time": {
"type": "integer",
"unit": "ms",
"minimum": 5,
"maximum": 65000,
"default": 1000
},
"Downtime alarm": {
"type": "integer",
"unit": "ms",
"minimum": 0,
"maximum": 20000,
"default": 100
},
"Buffering allowed": {
"type": "boolean"
},
"Enable reset after buffering": {
"type": "boolean"
}
},
"forms": [
{
"op": [
"writeproperty",
"readproperty"
],
"href": "profinet://127.0.0.1/0/1?api=0&index=1&datalength=14",
"contentType": "application/octet-stream",
"profv:type": "object",
"profv:pollingTime": 200,
"profv:payloadMapping": {
"Buffer time 2": {
"profv:type": "Unsigned16",
"profv:byteOffset": 2,
"profv:byteLength": 2
},
"Buffer threshold voltage": {
"profv:type": "Unsigned16",
"profv:byteOffset": 4,
"profv:byteLength": 2
},
"Stop buffering threshold voltage": {
"profv:type": "Unsigned16",
"profv:byteOffset": 6,
"profv:byteLength": 2
},
"Input voltage OK time": {
"profv:type": "Unsigned16",
"profv:byteOffset": 8,
"profv:byteLength": 2
},
"Downtime alarm": {
"profv:type": "Unsigned16",
"profv:byteOffset": 10,
"profv:byteLength": 2
},
"Buffering allowed": {
"profv:type": "boolean",
"profv:byteOffset": 12,
"profv:byteLength": 1,
"profv:bitOffset": 0,
"profv:enumeratedValue": [
{
"profv:encondedPayload": 0,
"profv:decodedPayload": false
},
{
"profv:encondedPayload": 1,
"profv:decodedPayload": true
}
]
},
"Enable reset after buffering": {
"profv:type": "boolean",
"profv:byteOffset": 13,
"profv:byteLength": 1,
"profv:bitOffset": 0,
"profv:enumeratedValue": [
{
"profv:encondedPayload": 0,
"profv:decodedPayload": false
},
{
"profv:encondedPayload": 1,
"profv:decodedPayload": true
}
]
}
}
}
]
}
}
}
The following describe the [[[#url]]] using [[[RFC2234]]] with the reference to [[[uri]]] specification.
PROFINET-URI = "profinet://" authority path-profinet [ "?api=" api, "?index=" index, "?datalength=" datalength ]
path-profinet = "/" slot "/" subslot
slot=1*DIGIT
subslot=1*DIGIT
api=1*DIGIT
index=1*DIGIT
datalength=4*DIGIT