Hi,
I’ve got a beginner type question concerning data acquisition.
I’m attempting to write a windows application with Measurement Studio, Visual Studio 2005 VB.net) and the NI USB-2009 DAQ.
Eventually, I would like to be reading ai’s and di’s on the clock (say 10 times a second). The ao’s and do’s will be written as required.
Right now, I would simply like to read a single ai “DEV1/ai0” and display the updating value in a textbox. Once I get a single value updating properly, the others should fall into place.
In the code I’ve included, I create a task to input the ai0 input value. When it runs, it calls the “Callback” routine and does update the “txtRegAirPressure.text” textbox. However, as expected, it only runs once. I would like the input task to run continuously to bring the ai in at the desired rate, but I also need the user to be able to interact with the application to perform other functions. I thought that the task is supposed to run as a separate thread acquiring data while allowing other tasks (such as di’s on the clock and the user interface) to continue.
So, my question is… What am I missing? I’m sure this must be fairly easy, but I’ve tried a number of permutations in the setup and cannot get where I want to be.
Hopefully, someone has the answer and will guide me in the right direction to which I will be very grateful!
Thanks in advance for taking a look!
Private myTask As Task
Private analogInReader As AnalogMultiChannelReader
Private analogCallback As AsyncCallback
Private Sub frmMain_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
' Create a new task
myTask = New Task
' Create a virtual channel
myTask.AIChannels.CreateVoltageChannel("Dev1/ai0", "", AITerminalConfiguration.Rse, 0.0, 5.0, AIVoltageUnits.Volts)
myTask.Timing.ConfigureSampleClock("", 10000.0, SampleClockActiveEdge.Rising, SampleQuantityMode.ContinuousSamples, 1000)
' Verify the task
myTask.Control(TaskAction.Verify)
analogInReader = New AnalogMultiChannelReader(myTask.Stream)
'' For .NET Framework 2.0, use SynchronizeCallbacks to specify that the object marshalls callbacks across the
'' threads appropriately.
analogInReader.SynchronizeCallbacks = True
analogCallback = New AsyncCallback(AddressOf AnalogInCallback)
analogInReader.BeginReadMultiSample(1000.0, analogCallback, Nothing)
End Sub
Private Sub AnalogInCallback(ByVal ar As IAsyncResult)
Dim data() As Double = analogInReader.ReadSingleSample
txtRegAirPressure.Text = data(0)
End Sub
