readAtTime
Read data from an OPC HDA server at specified times
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 time
stamps specified by TimeStamps
. HdaClient
must
be a scalar connected OPC HDA Client. ItmList
is a character
vector, string, or array defining one or more Fully Qualified ItemIDs in the name
space of the OPC Server. TimeStamps
must be a vector of MATLAB
date numbers. DObj
is returned as an opc.hda.Data
object array the same size as the number of items
specified by ItmList
. Each element of DObj
is
guaranteed to have the same time stamp as the other elements of
DObj
.
When no value exists for a specified time stamp, the server will interpolate a
value from the surrounding values to represent the value at that time stamp, and the
Quality
for that time stamp will include the
Interpolated
bit.
[ItmList,Value,Quality,TimeStamp]
= readAtTime(HdaClient,ItmList,TimeStamps,'
where DataType
')'DataType'
is one of the built-in MATLAB numeric arrays
('double'
, 'single'
, etc.) or
'cell'
, returns the data in the specified data type.
ItmID
is returned as a 1-by-N cell array of character
vectors. Value
is an array of M-by-N values.
Quality
is an array of M-by-N quality IDs, and
TimeStamp
is a M-by-1 array of time stamps as MATLAB date
numbers.
S = readAtTime(HdaClient,ItmList,TimeStamps,'struct')
returns a structure containing the fields ItemID
,
Value
, Quality
and
TimeStamp
.
Examples
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'},[now-1/24:10/86400:now]);
Version History
Introduced in R2015b