opcda

Create OPC data access object

Syntax

DAobj = opcda(HostID,ServerID)

DAobj = opcda(HostID,ServerID,Name,Value)

Description

DAobj = opcda(HostID,ServerID) creates an OPC data access object, DAobj, for the host specified by Host and the OPC server ID specified by ServerID. When you create DAobj, its initial Status property value is 'disconnected'. To communicate with the server, you must connect DAobj to the server with the connect function.

DAobj = opcda(HostID,ServerID,Name,Value) creates an OPC DA object, DAobj, for the host specified by Host and the OPC server ID specified by ServerID, applying the specified property values. If you specify an invalid property name or value, the function does not create an object.

For a complete listing of OPC Toolbox™ functions and properties, type opchelp.

Examples

Create OPC DA Clients

These examples show how to create OPC DA clients for local and remote servers.

Create an OPC DA client for a local server.

daObj1 = opcda('localhost','Dummy.Server.ID');

Create an OPC DA client for a remote server.

daObj2 = opcda('ServerHost1','OPCServer.ID');

Input Arguments

HostID — OPC server host name or IP address

char | string

OPC server host name or IP address, specified as a character vector or string.

Example: 'localhost'

Data Types: char | string

ServerID — OPC server ID

char | string

OPC server ID, specified as a character vector or string.

Example: 'OPCsrvhost'

Data Types: char | string

Name-Value Pair Arguments

Specify optional comma-separated pairs of Name,Value arguments. Name is the argument name and Value is the corresponding value. Name must appear inside quotes. You can specify several name and value pair arguments in any order as Name1,Value1,...,NameN,ValueN.

Example: 'Timeout',60

The property name-value pairs can be any format that the set function supports, i.e., name-value pairs, structures, and name-value cell array pairs. You can specify the writeable properties described in Output Arguments, including the following.

'Timeout' — Maximum time to wait for completion of instruction to server

10 (default)

Maximum time to wait for completion of instruction to server, specified in seconds.

Example: 60

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

'UserData' — Data to associate with object

any MATLAB data type

Data to associate with object, specified as any MATLAB data type. UserData stores any data that you want to associate with the object. The object does not use this data directly, but you can use the data for identification or other purposes.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | logical | char | struct | string | cell

Output Arguments

DAobj — OPC DA client

opcda object

OPC DA client, returned as an opcda object, with the following properties.

Property	Description
Host	DNS host name or IP address of server (read-only)
ServerID	Server identity (read-only)
Status	Status of connection to OPC server (read-only)
Timeout	Maximum time allowed for all operations on the server to complete
Group	Data access group objects contained by client (read-only)
Name	Descriptive name for OPC DA client object
Tag	Label to associate with OPC DA client object
Type	OPC Toolbox object type (read-only)
UserData	Data to associate with OPC DA client object
ErrorFcn	Callback function to execute when error event occurs
EventLog	Event information log (read-only)
EventLogMax	Maximum number of events to store in event log
ShutDownFcn	Callback function to execute when OPC server shuts down
TimerFcn	Callback function to execute when predefined period passes
TimerPeriod	Period between timer events (read-only while logging)

For information on any of these properties, type opchelp opcda.PropName, for example:

opchelp opcda.TimerPeriod