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Problems setting up analog or digital trigger input on OM-USB-1608FS


Walid
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Hi,

I am trying to understand how to programmatically setup the triggers on the USB-1608FS board so that I can:

1. Read data on the rising edge with trigger level set to 0, similar to the screen shot in TracerDAQ shown below (and showing the trigger options) which gives a stable sine wave starting at 0 for a sine wave input.

2. Read data on the external trigger input from a digital signal (I'm assuming this should be more stable than 1)

I know this can be done with this board and my signals are good because it works fine with TracerDaq. I'm using VB.net, there are no examples provided that do this (the trigger examples only work for a "signal above" level and therefore do not correctly trigger on the rising edge which is what I'm getting as well no matter what I set the trigger condition to), and the user's manual is a little confusing regarding how to use ATrig and SetTrigger in conjunction with AInScan (it suggests it only works with an external trigger, but I know it can work with a channel trigger). I've tried multiple combinations and only get triggers above 0 instead of rising edge triggers (and thus the sine wave just slides around the start trigger depending on when the signal was found to be above 0 rather than a positive edge). I know that the AInScan is armed and waiting for a trigger above 0 because it doesn't return a scan unless that is the case. Also pretriggering via ATrig apparently is not an option for this board.

The code snippet for setting up triggering that loops is:

           ULStat = DaqBoard.StopBackground(MccDaq.FunctionType.AiFunction) 'stop background scan for each trigger event
           Dim TrigVal As UShort = 32767
           Count = 2000    ' total number of data points to collect
                ' per channel sampling rate ((samples per second) per channel)
                Rate = 10000 / ((HighChan - LowChan) + 1)
               

                'Set up trigger

                ULStat = DaqBoard.ATrig(0, MccDaq.TriggerType.TrigAbove, TrigVal, Range, DataValue)
                ULStat = DaqBoard.SetTrigger(MccDaq.TriggerType.TrigPosEdge, TrigVal, TrigVal)
                Options = MccDaq.ScanOptions.Background

               'Expect AInScan to now wait for trigger rising edge above 0 but instead get trigger at any value above 0

                ULStat = DaqBoard.AInScan(LowChan, HighChan, Count, Rate, Range, MemHandle, Options)
                If ULStat.Value <> MccDaq.ErrorInfo.ErrorCode.NoErrors Then Stop
 

and I read it below with a timer (ADData always gives a shifted sine wave instead of one triggering on the rising edge):

     If Status = MccDaq.MccBoard.Running And UserTerm = 0 Then
            lblShowStat.Text = "Running"
            tmrCheckStatus.Start()

        ElseIf Status = MccDaq.MccBoard.Idle Or UserTerm = 1 Then
            lblShowStat.Text = "Idle"
            ULStat = DaqBoard.GetStatus(Status, CurCount, CurIndex, MccDaq.FunctionType.AiFunction)

            If ULStat.Value <> MccDaq.ErrorInfo.ErrorCode.NoErrors Then Stop

            lblShowCount.Text = CurCount.ToString("D")
            lblShowIndex.Text = CurIndex.ToString("D")
            If SwitchScan.Value = False Then
                tmrCheckStatus.Stop()
            End If
            If MemHandle = 0 Then Stop

            If ADResolution > 16 Then
                ULStat = MccDaq.MccService.WinBufToArray32(MemHandle, ADData32, FirstPoint, NumPoints)
                If ULStat.Value <> MccDaq.ErrorInfo.ErrorCode.NoErrors Then Stop

                For i = 0 To HighChan
                    lblADData(i).Text = ADData32(i).ToString("D")
                Next i
            Else
                ULStat = MccDaq.MccService.WinBufToArray(MemHandle, ADData, FirstPoint, NumPoints)
                If ULStat.Value <> MccDaq.ErrorInfo.ErrorCode.NoErrors Then Stop

            End If

Any advice would be greatly appreciated--a very simple flowchart with the procedure for setting up the board for proper rising edge channel 0 triggering would suffice, and then how to do it with a digital external trigger signal with this board as well.

Thanks,

Walid

 

image.png.39ed0280e380d4355786dfdb9c6cc365.png

Edited by Walid
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Hello @Walid.

The two functions are separate.

With the USB-1608FS module, the supported trigger option for the AinScan() function is an external digital (TTL) trigger.  The two supported trigger types are positive and negative edges.

image.png

 

image.png

 

As stated in the 'UL Help' documentation, "ATrig() waits for a specified analog input channel to go above or below a specified value. ATrig() continuously reads the specified channel and compares its value to trigValue. Depending on whether trigType is set to TrigAbove or TrigBelow, it waits for the first A/D sample that is above or below trigValue. The first sample that meets the trigger criteria is returned to dataValue."  It does not capture the specified value; 0V in your case.  A single value is captured with the ATrig() function.

Regards,

Fausto

 

Edited by Fausto
Added TracerDAQ screen capture.
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