readAtTime

Read data from an OPC HDA server at specified times

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    Syntax

    dObj = readAtTime(hdaClient,itmList,timeStamps)
    [itmList,value,quality,timeStamp] = readAtTime(hdaClient,itmList,timeStamps,dataType)
    S = readAtTime(hdaClient,itmList,timeStamps,'struct')

    Description

    dObj = readAtTime(hdaClient,itmList,timeStamps) reads data from the items defined by itmList, from the OPC HDA Server associated with client object hdaClient, at the timestamps specified by timeStamps.

    When no value exists for a specified timestamp, the server will interpolate a value from the surrounding values to represent the value at that timestamp, and the Quality for that timestamp will include the Interpolated bit.

    [itmList,value,quality,timeStamp] = readAtTime(hdaClient,itmList,timeStamps,dataType) returns the value in the specified dataType along with the corresponding item ID, quality ID and timestamp.

    S = readAtTime(hdaClient,itmList,timeStamps,'struct') returns a structure containing the fields ItemID, Value, Quality and TimeStamp.

    example

    Examples

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    Create an OPC HDA Client and connect the client to the server.

    hdaObj = opchda('localhost','Matrikon.OPC.Simulation');
connect(hdaObj);

    Read the values of two items every 10 seconds for the last hour.

    dObj = readAtTime(hdaObj,{'Random.Real8','Random.Real4'},[datetime("now")-hours(1):seconds(10):datetime("now")]);

    Input Arguments

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    OPC HDA client, specified as an OPC HDA client object. You can specify only one OPC HDA client, and the client must be connected to the server.

    Example: hdaClient = opchda(_)

    IDs of HDA items IDs, specified as a character vector, string, or supporting array of either.

    Example: {'Random.Real8','Random.Real4'}

    Data Types: char | string | cell

    Time boundaries, specified as datetime values returned by datetime function.

    Example: datetime(2018,11,28)

    Data Types: datetime

    Type of data in Value, specified as one of these:

    • 'single'

    • 'double'

    • 'int8'

    • 'int16'

    • 'int32'

    • 'int64'

    • 'uint8'

    • 'uint16'

    • 'uint32'

    • 'uint64'

    • 'logical'

    Output Arguments

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    Raw OPC HDA data, returned as an OPC HDA data object or an array of OPC HDA data objects. Each item in the itemList corresponds to a data object in the array. All elements in the dObj have the same timestamp.

    HDA item IDs, returned as a 1-by-N cell array of character vectors.

    HDA data, returned as a M-by-N array, where each element is of the same data type as specified in DataType.

    HDA data quality, returned as an M-by-N array of quality IDs.

    Timestamp of data read from server, returned as an M-by-1 vector of timestamps.

    Version History

    Introduced in R2015b

    See Also

    Functions