Genral How do I get syncronize​d encoders to work with a PCI-6602

Question

I am new to the DAQmx and need some general help writting VB code that works.
I can get some things to work, but others don't work at all and I don't have enough knowledge of these drivers to get up the learnign curve hump.
I wanted to post this as a follow-up
to the thread:
http://forums.ni.com/ni/board/message?board.id=40&​message.id=5430&query.id=215100#M5430
But I couldn’t figure out how.  
Anyway, my problem is that I will
eventually have to do much the same thing as the above thread with two encoders in
sync.
I have a pci-6602 card, and my code
snippet is at the bottom  The 6602 doesn't have the analog in to syncronize to like the thread above
  (yes, it is in Visual basic
6)
I can’t figure out the
DAQmxCfgSampClkTiming.   Why do I want to have a sample clock at all?   (okay,
when I have two channels synced I do – but this sample I want to get working and
I don’t see why)?
Can’t I just get a new counter value
with each quadrature input change?   (That’s what the DEV/PFI39 is, the same as
encoder channel A )
Okay, so hopefully you tell me how
to get that to work.
Next question:  What can I use for
the DAQmxCfgSampClkTiming when I am doing two channels in sync?  Nothing seems
to work, and I have tried a bunch of things.
Brynn
Rogers
DeltaTech
Controls
952-403-7400
x431
//// code that doesn't really work.   "Dev1/PFI39" is the channel A encoder input, I just want new data whenever the encoder changes (for now)
    ' DAQmx Configure
Code
    DAQmxErrChk
DAQmxCreateTask("count", TaskHandle)
    TaskIsRunning =
True
    DAQmxErrChk
DAQmxCreateCIAngEncoderChan(TaskHandle, "Dev1/ctr0", "",
DAQmx_Val_EncoderType2_X4, 0, 0#, DAQmx_Val_EncoderZIndexPhase1_AHighBHigh,
DAQmx_Val_AngleUnits2_Ticks, 500, 0#, "")
    DAQmxErrChk
DAQmxCfgSampClkTiming(TaskHandle, "Dev1/PFI39", 1, DAQmx_Val_Rising,
DAQmx_Val_AcquisitionType_FiniteSamps, samples)
    'DAQmx Start
Code
    DAQmxErrChk
DAQmxStartTask(TaskHandle)
    ' DAQmx Read
Code
    DAQmxErrChk
DAQmxReadCounterF64(TaskHandle, -1, 0.05 * samples, data(0), samples, ReadCount,
ByVal 0&)
    ' All done!
StopTask
    'DAQmxErrChk
DAQmxStopTask(TaskHandle)
    'Stop task isn't needed because
Clear Task also stops task
    DAQmxErrChk
DAQmxClearTask(TaskHandle)
Solved!
Go to Solution.

Answer 1

Okay,   Here is the working routine to get syncronous data from two encoders, and it seems to work okay.
   I have this working with my two 2000 CPR encoders, we'll see how it works when I get the 500,000 CPR encoders later.
The three big problems that caused it to not work were:  
1)   Theduty cycle argument for the createCOpulsechanfreq task needed to be between 0 and 1.  I had '50.0' before, it works when it is '0.5'
2)   The sample timebase that I used (ctr7) needed to be started before either of my two angle encoder tasks were created
3)   The "dev/PFI8" string needed to be changed to "/dev/PFI8".   I don't really understand why, but that was what seemed to fix it all.
So this question has been answered...      Now I have a different problem while reading 8 PWM values at once with the Semiperiodcounter,  which I will post in a new a different thread.
Thanks!
''''''''''''''''''   Working code here
Public Sub Aquireposition(samples As Long, data0() As Double, data1() As Double)
Dim BaseTaskHandle    As Long
Dim encoder0TaskHandle    As Long
Dim encoder1TaskHandle    As Long
Dim TaskIsRunning As Boolean
Dim ReadCount As Long
Dim strCounterString As String
   On Error GoTo ErrorHandler
    DAQmxErrChk DAQmxCreateTask("base", BaseTaskHandle)
    DAQmxErrChk DAQmxCreateCOPulseChanFreq(BaseTaskHandle, "/Dev1/ctr7", "base", DAQmx_Val_FrequencyUnits2_Hz, DAQmx_Val_Level1_Low, 0#, 200#, 0.5)
'Specify continuous timing
    DAQmxErrChk DAQmxCfgImplicitTiming(BaseTaskHandle, DAQmx_Val_AcquisitionType_ContSamps, 200)
     'DAQmx Start Code
    DAQmxErrChk DAQmxStartTask(BaseTaskHandle)
' DAQmx Configure Code
    DAQmxErrChk DAQmxCreateTask("encoder", encoder0TaskHandle)
    TaskIsRunning = True
    DAQmxErrChk DAQmxCreateCIAngEncoderChan(encoder0TaskHandle, "/Dev1/ctr0", "", DAQmx_Val_EncoderType2_X4, 0, 0#, DAQmx_Val_EncoderZIndexPhase1_AHighBHigh, DAQmx_Val_AngleUnits2_Degrees, 500, 0#, "")
    DAQmxErrChk DAQmxCfgSampClkTiming(encoder0TaskHandle, "/Dev1/PFI8", 1, DAQmx_Val_Rising, DAQmx_Val_AcquisitionType_FiniteSamps, samples)
    ' second encoder
    DAQmxErrChk DAQmxCreateTask("encoder1", encoder1TaskHandle)
    TaskIsRunning = True
    DAQmxErrChk DAQmxCreateCIAngEncoderChan(encoder1TaskHandle, "/Dev1/ctr1", "", DAQmx_Val_EncoderType2_X4, 0, 0#, DAQmx_Val_EncoderZIndexPhase1_AHighBHigh, DAQmx_Val_AngleUnits2_Degrees, 500, 0#, "")
    DAQmxErrChk DAQmxCfgSampClkTiming(encoder1TaskHandle, "/Dev1/PFI8", 1, DAQmx_Val_Rising, DAQmx_Val_AcquisitionType_FiniteSamps, samples)
    'DAQmx Start Code
    DAQmxErrChk DAQmxStartTask(encoder0TaskHandle)
    DAQmxErrChk DAQmxStartTask(encoder1TaskHandle)
    ' DAQmx Read Code
    DAQmxErrChk DAQmxReadCounterF64(encoder0TaskHandle, -1, 0.05 * samples, data0(0), samples, ReadCount, ByVal 0&)
    DAQmxErrChk DAQmxReadCounterF64(encoder1TaskHandle, -1, 0.05 * samples, data1(0), samples, ReadCount, ByVal 0&)
    ' All done! StopTask
    'DAQmxErrChk DAQmxStopTask(TaskHandle)
    'Stop task isn't needed because Clear Task also stops task
    DAQmxErrChk DAQmxClearTask(encoder0TaskHandle)
    DAQmxErrChk DAQmxClearTask(encoder1TaskHandle)
    DAQmxErrChk DAQmxClearTask(BaseTaskHandle)
    Exit Sub
ErrorHandler:
'   MsgBox "Error: " & Err.Number & " " & Err.Description, , "Error"
'    mlngPWM_ErrorCount(lngChannel) = mlngPWM_ErrorCount(lngChannel) + 1
    'MainForm.PWMErrorCount = "Errors(" & lngChannel & "): " & mlngPWM_ErrorCount(lngChannel)
    Resume Next
End Sub