This is a continuation of my previous post.
I am pasting some source code that demonstrates the problem.
Create a C# WinForms project. Name the form MainForm.
Add two buttons named _StartBtn and _StopBtn. Hook up the Click event handlers for these
buttons to the corresponding methods below.
Compile and run this program. Alternately press the start button and then the stop button.
When the start button is pressed the 9th time the program will fail.
Note my code is different than the ContAcqVoltageSamples_IntClk sample program in the
Measurement Studio documentation in that I do not delete the Task after I
stop it and create a new one before I start it.
( I don't see why you should not be able to restart an existing Task once it has been stopped).
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using NationalInstruments.DAQmx;
namespace DataAcqTest
{
public partial class MainForm : Form
{
private Task _AcqTask;
private AnalogMultiChannelReader _Reader;
private AsyncCallback _SampleBufferFilled;
private Boolean _ContinueRunning;
private readonly Double _SampleRate = 15000.0;
private readonly Int32 _NumSamplesToReadAtATime = 1500;
public MainForm()
{
InitializeComponent();
}
private void MainForm_Load(object sender, EventArgs e)
{
_SampleBufferFilled = new AsyncCallback(this.SampleBufferFilled);
_AcqTask = new Task("DemoAnalogInTask");
for (int i = 0; i < 4; i++)
{
_AcqTask.AIChannels.CreateVoltageChannel("NI-9215-1/ai" + i.ToString(),
"",
AITerminalConfiguration.Differential,
-10.0,
+10.0,
AIVoltageUnits.Volts);
}
_AcqTask.Timing.ConfigureSampleClock(String.Empty, // signal source is internal clock
_SampleRate,
SampleClockActiveEdge.Rising,
SampleQuantityMode.ContinuousSamples,
_NumSamplesToReadAtATime);
_AcqTask.Control(TaskAction.Commit);
_Reader = new AnalogMultiChannelReader(_AcqTask.Stream);
_Reader.SynchronizeCallbacks = true;
_StopBtn.Enabled = false;
}
private void StartBtn_Click(object sender, EventArgs e)
{
_ContinueRunning = true;
_StartBtn.Enabled = false;
_StopBtn.Enabled = true;
_Reader.BeginReadMultiSample(_NumSamplesToReadAtATime,
_SampleBufferFilled,
null);
}
private void StopBtn_Click(object sender, EventArgs e)
{
_ContinueRunning = false;
_StopBtn.Enabled = false;
}
private void SampleBufferFilled(IAsyncResult ar)
{
Double[/*channel*/, /*sample*/] channelsSamples = _Reader.EndReadMultiSample(ar);
if (_ContinueRunning)
{
_Reader.BeginReadMultiSample(_NumSamplesToReadAtATime,
_SampleBufferFilled,
this);
}
else
{
_AcqTask.Stop(); // Goes to the committed state
_StartBtn.Enabled = true;
}
}
}
}
