Trigger From My Laser - 25us pulse with USB-6212 BNC

[IdealVac]

 Thank you for your help. We are using a USB-6212 BNC and want to trigger our analog data collection with our laser the produces a 25 us TTL +5 V pulse. Each time the laser fires I want to collect analog data. I called tech support and they said I need to do Analog Input with Hardware Trigger. I have code to do analog input, no problem. I do not know how to do this triggering. Can you send me a sample of code to do this? I am using VB.NET 4.5 Visual Basic 2012. Thank you. Tony

[James-B]

Hi IdealVac,

A good place to start for everything Measurement Studio is:

http://www.ni.com/white-paper/14430/en/ 

As for examples, they are located in the start menu at

All Programs->National Instruments->NI-DAQ->Text-Based Code Support->DotNet4.5 Examples.

From there, navigate to Analog In->Measure Voltage, and there are a bunch of examples.  I think I would start with "AcqVoltageSamples_IntClkDigRef"

Perhaps somebody else has worked with these more and could share their thoughts too.

[IdealVac]

Hi James,

Thank you for your help. I am a little behind the "8 ball" here and could use some code examples. All I need is a couple sub routines for hardware triggering. That is, I want my VB.Net 2012 software to stand still until the USB-6212 revcieves a pulse from by laser (TTL 5 V, 25 us wide pulses, at 10 Hz). I need the hardware to send a signal to my subroutine to collect data. My laser fires 10 times a second and my software needs to be trigger after each laser shot. I think that this will have to be done with event and callback handling but I am not an expert.

I looked at your suggestion

C:\Users\Public\Documents\National Instruments\NI-DAQ\Examples\DotNET4.5\Analog In\Measure Voltage\AcqVoltageSamples_IntClkDigRef

and it does work once to collect data when a TTL trigger arrives at PFI0. Do not know how to modify so that I get a callback each time I get a laser TTL pulse at PFI0?

 Question, what simple pair of text based VB.Net 4.5 sub routines would hardware monitor for a trigger pulse on PFI0 and each time a pulse arrives it runs a second sub routine that flash a little LED like light on my mainform? If I had this I could finish my project.

Thank you very much for your help. Tony

******* Sample code from AcqVoltageSamples_IntClkDigRef ****************************

    Private Sub startButton_Click_1(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles startButton.Click
        startButton.Enabled = False
        Try
            'Create a new Task
            myTask = New Task()

            'Initialize Local Variables
            Dim sampleRate As Double = Convert.ToDouble(rateNumeric.Value)
            Dim rangeMin As Double = Convert.ToDouble(minimumValueNumeric.Value)
            Dim rangeMax As Double = Convert.ToDouble(maximumValueNumeric.Value)
            Dim samplesPerChan As Int32 = Convert.ToInt32(samplesPerChanNumeric.Value)

            'Create a channel
            myTask.AIChannels.CreateVoltageChannel(physicalChannelComboBox.Text, "", CType(-1, AITerminalConfiguration), rangeMin, rangeMax, AIVoltageUnits.Volts)

            'Configure Timing Specs
            myTask.Timing.ConfigureSampleClock("", sampleRate, SampleClockActiveEdge.Rising, SampleQuantityMode.FiniteSamples, samplesPerChan)

            ' Configure Reference Trigger
            myTask.Triggers.ReferenceTrigger.ConfigureDigitalEdgeTrigger(referenceTriggerSourceTextBox.Text, referenceEdge, preTriggerNumeric.Value)

            ' Verify the Task
            myTask.Control(TaskAction.Verify)
            reader = New AnalogMultiChannelReader(myTask.Stream)

            ' Use SynchronizeCallbacks to specify that the object
            ' marshals callbacks across threads appropriately.
            reader.SynchronizeCallbacks = True
            reader.BeginReadWaveform(samplesPerChan, AddressOf myCallback, Nothing)

            ' Prepare the table for Data
            InitializeDataTable(myTask.AIChannels, dataTable)
            acquisitionDataGrid.DataSource = dataTable
        Catch e1 As DaqException
            MessageBox.Show(e1.Message)
            myTask.Dispose()
            startButton.Enabled = True
        End Try
    End Sub

    Private Sub myCallback(ByVal ar As IAsyncResult)
        Try
            ' Read the available data from the channels
            Dim data() As AnalogWaveform(Of Double) = reader.EndReadWaveform(ar)

            ' Plot your data here
            dataToDataTable(data, DataTable)

        Catch e1 As DaqException
            MessageBox.Show(e1.Message)
        Finally
            startButton.Enabled = True
            myTask.Dispose()
        End Try
    End Sub

[IdealVac]

Got it to work! I am not sure this is the best way but it runs like I want it to. Basically, I want my data collection myCallback(ByVal ar AsIAsyncResult) analog input voltage measurement sub routine code to stay at rest until a digital input TTL trigger pulses from by laser (occurs at 10 Hz, +5 V, 25 us wide) is received at the hardware USB-6212 PFI1/P1.1 port. At that time, the runallthetime()  calls my  myCallback(ByVal ar AsIAsyncResult)  sub routine and data collection is executed. The trick is to have the myCallback(ByVal ar AsIAsyncResult) sub loop back to the runallthetime()  hardware trigger sub. See below. This makes a continuous running software that will collect 1 point of AI0 data every time a trigger is detected on PFI1/P1.1.

Private Sub startButton_Click_1(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles startButton.Click         startButton.Enabled =False         runallthetime() EndSub

PrivateSub myCallback(ByVal ar AsIAsyncResult)      Try           'The variable data is an Array (x,y), it will be get (1) data point for each Virtual Channel below in                   'myTask.AIChannels.CreateVoltageChannel("Dev1/ai0, Dev1/ai1, Dev1/ai2, Dev1/ai3",             data = reader.ReadMultiSample(1)             TextBox3.Text =CStr(data(0, 0))      Finally                 myTask.Dispose()      EndTry                 runallthetime() 'Hardware Trigger CallBack EndSub

PrivateSub runallthetime()        Try                           'Create a new task                    myTask = NewTask()                    'Create a virtual channel - physicalChannelComboBox.Text                   myTask.AIChannels.CreateVoltageChannel("Dev1/ai0, Dev1/ai1, Dev1/ai2, Dev1/ai3", "", AITerminalConfiguration.Rse, Convert.ToDouble("-10"), Convert.ToDouble("10"), AIVoltageUnits.Volts)

                 'Configure Timing Specs                  'myTask.Timing.ConfigureSampleClock("", 100, SampleClockActiveEdge.Rising, SampleQuantityMode.FiniteSamples,                 ' samplesPerChan)                   myTask.Timing.ConfigureSampleClock("", 100, SampleClockActiveEdge.Rising, SampleQuantityMode.FiniteSamples, 10)

                'Simple Start Tigger Function - Has Two Parameters (Channel = /Dev1/PFI0 - PFI7,                 'DigitalEdgeReferenceTriggerEdge.Rising or Falling                  myTask.Triggers.StartTrigger.ConfigureDigitalEdgeTrigger("/Dev1/PFI1", DigitalEdgeStartTriggerEdge.Rising)

               ' Verify the Task                  myTask.Control(TaskAction.Verify)                  reader = NewAnalogMultiChannelReader(myTask.Stream)

               ' Use SynchronizeCallbacks to specify that the object                 ' marshals callbacks across threads appropriately.                  reader.SynchronizeCallbacks =True                  reader.BeginReadWaveform(1,  AddressOf myCallback, Nothing)

      Catch e1 AsDaqException                 startButton.Enabled =True       EndTry EndSub

[IdealVac]

    Private Sub startButton_Click_1(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles startButton.Click
        startButton.Enabled = False
        runallthetime()
    End Sub

    Private Sub myCallback(ByVal ar As IAsyncResult)
        Try
            'The variable data is an Array (x,y), it will be get (1) data point for each Virtual Channel below in myTask.AIChannels.CreateVoltageChannel("Dev1/ai0, Dev1/ai1, Dev1/ai2, Dev1/ai3",
            data = reader.ReadMultiSample(1)
            TextBox3.Text = CStr(data(0, 0))
        Finally
            myTask.Dispose()
        End Try
        runallthetime()
    End Sub

    Private Sub runallthetime()
        Try

            'Create a new task
            myTask = New Task()

            'Create a virtual channel - physicalChannelComboBox.Text
            myTask.AIChannels.CreateVoltageChannel("Dev1/ai0, Dev1/ai1, Dev1/ai2, Dev1/ai3", "", AITerminalConfiguration.Rse, Convert.ToDouble("-10"), Convert.ToDouble("10"), AIVoltageUnits.Volts)

            'Configure Timing Specs 
            'myTask.Timing.ConfigureSampleClock("", 100, SampleClockActiveEdge.Rising, SampleQuantityMode.FiniteSamples, samplesPerChan)
            myTask.Timing.ConfigureSampleClock("", 100, SampleClockActiveEdge.Rising, SampleQuantityMode.FiniteSamples, 10)

            'Simple Start Tigger Function - Has Two Parameters (Channel = /Dev1/PFI0 - PFI7,DigitalEdgeReferenceTriggerEdge.Rising or Falling 
            myTask.Triggers.StartTrigger.ConfigureDigitalEdgeTrigger("/Dev1/PFI1", DigitalEdgeStartTriggerEdge.Rising)

            ' Verify the Task
            myTask.Control(TaskAction.Verify)
            reader = New AnalogMultiChannelReader(myTask.Stream)

            ' Use SynchronizeCallbacks to specify that the object 
            ' marshals callbacks across threads appropriately.
            reader.SynchronizeCallbacks = True
            reader.BeginReadWaveform(1, AddressOf myCallback, Nothing)

        Catch e1 As DaqException

            startButton.Enabled = True
        End Try
    End Sub

[IdealVac]

Sorry, the two above codes are the same. I first pasted the code in the text editor section. The one directly above is correct, i used the insert code function :-). Thanks.