I'm having probles with writing voltages in a .txt file with a ni USB-6008

[Newbie01]

Hi there, i'm trying to write a program in visual basic .net that writes the tension from 4 channel in a .txt file and since i'm a newbie i'm having a lot of problems with it 🙂

I tried to read the documentation and tried the nidaqmx examples but i wasn't able to finish it as i wanted to.

I'll post my code here

Imports System
Imports System.IO
Imports NationalInstruments.DAQmx

Public Class Form1
 
    Private myTask1 As Task                  'A new Task is created when the start button is pressed
    Private analogInReader As AnalogMultiChannelReader
    Private savedData As ArrayList
    Declare Function QueryPerformanceCounter Lib "Kernel32" (ByRef X As Long) As Short
    Declare Function QueryPerformanceFrequency Lib "Kernel32" (ByRef X As Long) As Short

    Sub startbutton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles startbutton.Click


        Dim minimumValueNumeric As Int32 = -10
        Dim maximumValueNumeric As Int32 = 10

        myTask1 = New Task()
        myTask1.AIChannels.CreateVoltageChannel("dev1/ai0:3", "Voltage", _
         CType(-1, AITerminalConfiguration), Convert.ToDouble(minimumValueNumeric), _
         Convert.ToDouble(maximumValueNumeric), AIVoltageUnits.Volts)

        myTask1.Timing.ConfigureSampleClock("", 1000, SampleClockActiveEdge.Rising, _
                                       SampleQuantityMode.ContinuousSamples)

        myTask1.Control(TaskAction.Verify)
        analogInReader = New AnalogMultiChannelReader(myTask1.Stream)





        Dim data() As Double = analogInReader.ReadSingleSample
        Dim i As Int32 = 0
        Dim countercicli As Int32 = 0
        '''''''''' For f = 0 To NumericUpDown1.Value - 1




        Dim Ctr1, Ctr2, Freq As Long


        If data(0) >= 1 Then
            i = i + 1

            Using w As StreamWriter = File.AppendText("c:\TestFile.txt")
                ' Add some text to the file.

                w.Write(i & "  " & data(0).ToString("n4") & "  " & data(1).ToString("n4") & "  " & data(2).ToString("n4") & "  " _
                            & data(3).ToString("n4") & "  ")
                countercicli = countercicli + 1
                If countercicli = 10 Then
                    Dim hail As Double
                    QueryPerformanceFrequency(Freq)
                    QueryPerformanceCounter(Ctr2)
                    hail = ((Ctr2 - Ctr1) / (Freq / 1000)).ToString("n4") 'milliseconds
                    If hail >= 1000 Then
                        hail = 10
                    End If
                    w.WriteLine("timer: {0}", hail)
                    countercicli = 0
                    Ctr1 = Ctr2
                End If
                If countercicli <> 10 And countercicli <> 0 Then
                    w.WriteLine("timer: {0}", 0)
                End If



            End Using
        End If

        '''''''''   Next
    End Sub

End Class

Basically i'm trying to get a continuous write of the tension of the 4 channels (only if the 3rd channel voltage is higher then 1 volt, which is my trigger) in the  TestFile.txt

Unfortunately for now i'm able to write only the first line and i have no idea how to make it continuous (if it's possible)

Any help will be appreciated, thanks in advance

[AndreaN]

Hello Newbie,

I can point you to a link in which is said where to find DAQmx VB.NET examples:

Text Based NI-DAQmx Data Acquisition Examples

http://zone.ni.com/devzone/cda/tut/p/id/6999#.NETAI 

In the Analog Input section there is an example called "Continuously Acquire Voltage Samples - Internal Clock - Save to File" that is installed when you install the NI DAQmx library. You should be able to find this example at the following location:

C:\Documents and Settings\All Users\Shared Documents\National Instruments\NI-DAQ\Examples\ 

I hope this can help, best regards.