OPC (OLE for Process Control)

OLE for Process Control (OPC) Device Driver allows Iotellect Server to communicate with OPC Servers, i.e. act as an OPC Client. Data provided by OPC Servers (and hardware devices "behind" them) is converted into unified form to allow access from different Iotellect facilities. See Devices article for more information about the "normalized" representation of devices in Iotellect.

Unlike most OPC Clients which require the OPC Server and OPC Client to reside on the same computer, Iotellect Server communicates with OPC Servers using Distributed COM (DCOM) technology. It allows Iotellect Server to access OPC Servers via IP networks or the Internet.

OPC device driver doesn’t work with OPC server installed on Windows systems that received DCOM+authentication+hardening">DCOM authentication hardening updates. There are other ways for accessing OPC servers installed on such Windows systems: Using Iotellect OPC Agent (Native OPC Client) that resides on the same machine with OPC server and communicated to it via COM instead of DCOM. OPC Agent uses Iotellect protocol to bridge OPC data to a Iotellect Server. Using a third-party OPC DA to OPC UA converter (gateway) and OPC UA device driver to inject OPC data into Iotellect Server.

Another advantage of using DCOM is that Iotellect Server provides access to OPC Servers from operating systems other than Microsoft Windows, including Linux/Unix.

Iotellect Server's OPC Driver supports the OPC Data Access specification. Support for other OPC Standards and Specifications, including OPC Alarm and Events, will be implemented in future versions of Iotellect.

In order to allow Iotellect Server to access your OPC Server, it's necessary to configure DCOM service on the machine running it for remote access. See Configuring DCOM for Remote Access for information on this subject.

Configuring DCOM protocol can be tricky. If you want to leverage “classic” OPC via COM, consider using OPC Agent (Native OPC Client). You can also upgrade to using OPC UA communications.

Due to Iotellect Server variable name limitations (roman letters, numbers and underscore sign) not all item name characters can be transformed to variable names directly. For items that name contains unsupported characters a name conversion is applied. Name conversion process is as follows:

• Iotellect Server tries automatically encode most widely used characters by its roman letters representation (similar to transcription). If representation was not found then underscore character is used.

• A hash code of the source item name is appended. To avoid duplicate names after the first step.

OPC device driver supports OPC server discovery. Discovery is the process of scanning a number of IP network hosts, finding available OPC servers, and creating device accounts for them.

The comprehensive description of OPC server discovery is available in Iotellect SCADA/HMI documentation.

Each of OPC items is represented as a variable with three fields:

The quality of OPC items is reported as status of corresponding device setting variables. To check the status of a certain setting, open OPC device configuration in the Properties Editor and hold mouse over the setting status icon. Item quality will be shown in the tooltip.

To see the quality of all items at once, open Settings Synchronization Status tab of device status dialog. Item quality is shown in the Synchronization Status field.

None defined.

None defined.

Connection settings define how Iotellect Server communicates with a certain OPC Server. These settings may be accessed using Edit Device Properties action of Device Context. Here is a list of available connection properties including advanced properties:

It it sufficient to specify either CLSID or PROGID of the OPC Server, not both of them.

This table allows to manually enter names of OPC tags/items to poll. This is suitable for OPC servers that do not implement or erroneously implement OPC item tree browsing.

Hierarchical structure of assets provided by the OPC device driver exactly matches tree-like structure of OPC item groups.

OPC device driver creates one Device setting variable for every OPC server item.

The following table shows how OPC types are converted to Iotellect types:

No operations provided by the driver.

No events provided by the driver.

This driver makes the device Online if:

• TCP connection to an OPC server was successfully established

• DCOM authorization did not fail

OPC Servers are synchronized with Iotellect Server like any other Devices. Synchronization between Iotellect Server and an OPC Server includes the following steps:

• Reading information about settings provided by OPC Server and creation of Settings Cache. Settings are divided into several groups, according to OPC Server's internal division.

• Reading OPC Server setting values and storing these values in settings cache.

View Device Status action of OPC Server's Device Context provides additional information about OPC Server status:

• Bandwidth

• Build Number

• Current Time

• Group Count

• Last Update Time

• Major Version

• Minor Version

• Server State (Available states are: Communication Failure, Failure, Configuration Error, Running, Suspended, Test and Unknown)

• Server State Code

• Start Time

• Vendor Information

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