readItemAttributes

Package: opc.hda

Read item attribute values from OPC HDA server

Syntax

S = readItemAttributes(HdaObj, ItemID, Attribute, StartTime, EndTime)

Description

S = readItemAttributes(HdaObj, ItemID, Attribute, StartTime, EndTime) reads item attribute values for the opc.hda.ItemAttributes item with ID ItemID. HdaObj must be a scalar OPC HDA client that is already connected to the server.

ItemID is a string containing the item ID for which attributes are requested. Attribute is the requested attribute for the item, specified either as a string or as the ID for that attribute. StartTime and EndTime are MATLAB date numbers representing the start and end times of the period over which data must be aggregated.

S is returned as a structure array containing fields ItemID, AttributeID, TimeStamp and Value. ItemID is the item ID requested. AttributeID is the numeric ID of the attribute requested. TimeStamp is a vector containing the time stamp(s) when the attribute was updated. Value is the value that the attribute was changed to at each time in TimeStamp.

The ItemAttributes property of the connected client object HdaObj contains all valid item attributes for the server.

Examples

Retrieve the current data type of the 'Random.Real8' property:

hdaObj = opchda('localhost','Matrikon.OPC.Simulation');
connect(hdaObj);
attrStruct = hdaObj.readItemAttributes('Random.Real8', ...
                 hdaObj.ItemAttributes.DATA_TYPE, now, now)
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