Changing to a different counter card yields no results

[jasonkelly214]

Hello,

I'm very new to Labview and so I was hoping that I might be able to get some help here. I've inherited a project and a lot of labview code, and as I piece through it I'm updating it, cleaning it up, and trying to modify it for new testing new products that we are releasing soon. I have a piece of code here that basically uses an NI PCI-6251 counter card to read in some digital waveforms. I'm trying to convert that code to work with the NI PCI-6602 counter card that we also have.

I basically pulled out the code that is at the base of our VI's that I need most and that has been causing me the biggest headaches. I have three I/O controls, NI6251/Ctr0, NI6251/Port0, NI6251/PFI12 and they work fine. When I switch them to NI6602/Ctr0, NI6602/Port0, NI6602/PFI12, then I get some errors having to do with the counter cards ability to sample.

Here is the error that I am getting:

Error - 200077 occurred at Property Node DAQmx Timing (arg 1) in DAQmx Timing (Sample Clock).vi:2->getwaveforms.vi

Possible reason(s):

Requested value is not a supported value for this property.

The property value may be invalid because it conflicts with another property.

Property: SampTimingType

Requested Value: Sample Clock

You Can Select: On Demand

Task Name: _unnamedTask<A2A4A>

When I try to select On Demand however from that dropdown menu, it is not listed. Any suggestions on what I need to do?

Thanks!

~Jason

[Dennis_Knutson]

As you can see from the specs, the digital I/O on the 6602 has software timing only. You cannot use the timing function at all to acquire a digital pattern. You acquire with a DAQmx Read in a loop. This sort of acquisition is slow and subject to quite a bit of jitter. The 6602 is a poor replacement if you need precise timing to acquire a digital signal with precise timing.

[Thomas-B]

Hi Jason, 

The behavior you are seeing is expected. The reason error -200077 is occurring, telling you cannot select Sample Clock on the your DAQmx Timing VI, is due to the fact that your PCI-6602 is not capable of performing hardware timing. You did not see this error with your PCI-6251 because it has hardware timing capabilities. 

Beause of this, you will have to have your application run with software timing. The reason the DAQmx Timing VI does not have the option for "on-demand" timing is because on-demand timing is the default setting with no DAQmx Timing VI. That specific VI is inteded to be used to configure hardware timing. Thus, if you remove the VI altogether, your applicaiton will run using software timing.  

Hopefully this helps.

[jasonkelly214]

Thank you both for your responses.

If I need to be able to sample at higher rates that software timing can allow for, am I able to use an external clock fed into the NI6602 board for triggering?

[Dennis_Knutson]

No. If you could do that, then the spec would not say software timed.

[jasonkelly214]

So I've switched to doing it with software timing, and I was able to get this before, but what I'm having trouble doing now it getting my waveform to concatenate data as it comes in. It is centering the data around zero, and instead of scrolling, or appending new data on, it simply overwrites. And I need to see the whole waveform, not just the bits flipping in place.

I've attached the VI