ValueSymbolExtensionsPollValues(ISumRead, TimeSpan) Method

C#

public static IObservable<ResultSumValues> PollValues(
    this ISumRead sumRead,
    TimeSpan period
)

Parameters

Return Value

IObservable ResultSumValues
IObservable<ResultSumValues>.

Usage Note

In Visual Basic and C#, you can call this method as an instance method on any object of type ISumRead. When you use instance method syntax to call this method, omit the first parameter. For more information, see Extension Methods (Visual Basic) or Extension Methods (C# Programming Guide).

Remarks

The characteristic of this overload is that more than one values can be read with one trigger signal. Each trigger produces only one Read call to the SumRead. Dependent on the configuration of the SumRead this could mean only one ADS Roundtrip (Request/Response). So the advantages are:

• Usage of one trigger (could be a Background thread resource) for all values
• Getting the values of all values in one ADS roundtrip
• Values inside the SumRead are more consistant dependant of target realtime task configuration.

Example

Demonstration of polling values efficiently via SumRead command.

Observe multiple ADS Symbols via Polling of SumCommand

// To Test the Observer run a project on the local PLC System (Port 851)
using (AdsClient client = new AdsClient())
{
    // Connect to target
    client.Connect(new AmsAddress(AmsNetId.Local, 851));

    // Create Symbol information
    var symbolLoader = SymbolLoaderFactory.Create(client, SymbolLoaderSettings.Default);
    IValueSymbol cycleCount = (IValueSymbol)symbolLoader.Symbols["TwinCAT_SystemInfoVarList._TaskInfo[1].CycleCount"];
    IValueSymbol lastExecTime = (IValueSymbol)symbolLoader.Symbols["TwinCAT_SystemInfoVarList._TaskInfo.LastExecTime"];
    List<ISymbol> symbols = new List<ISymbol>() { cycleCount, lastExecTime };

    //Create the SumCommand
    SumSymbolRead sumRead = new SumSymbolRead(client, symbols);

    // Reactive Notification Handler
    var sumCommandObserver = Observer.Create<ResultSumValues>(result =>
    {
    Console.WriteLine($"SumCommand Succeeded: {result.OverallSucceeded}, CycleCount: {result.Values[0]}, LastExecTime: {result.Values[1]}");
    }
    );

    // Take 20 Values/Result in an Interval of 500ms
    IDisposable subscription = sumRead.PollValues(TimeSpan.FromMilliseconds(500)).Take(20).Subscribe(sumCommandObserver);

    Console.ReadKey(); // Wait for Key press
    subscription.Dispose(); // Dispose the Subscription
}

Reference

ValueSymbolExtensions Class PollValues Overload TwinCAT.Ads.Reactive Namespace ISumRead PollValues2S(ISumRead2S, TimeSpan)

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