PCI 6110 in LabView 7 not triggering

[TJR_741]

I was previously working with LabView 5 on a Macintosh under OS 8. I have just upgraded to LabView 7 on WindowsXP. I was able to port my applications fairly easily using the Traditional NI-DAQ drivers. However, my fast data acquisition (on a PCI 6110 board) step is not triggering properly. I am seeing two problems that may or may not be related.

First, the hardware trigger is not being recognized. I can run the data acquisition at 5 MS/second without a trigger, and it does not have any problem keeping up with the data acquisition rate for the number of samples I am recording. I turn on the hardware trigger (analog, channel 1 or PFI0), and I get an 'AI Buffer Read' error because it never triggers the data acquisition. If I simply collect my trigger channel, it is a square pulse going from 0 to 5 V just as it should be, so I don't know why it is not triggering off of it.

Second, if I set my trigger voltage level above 0.3 V, it gives me the error message 'Trigger Level is Invalid'. That doesn't make any sense. The board can clearly see the full 0 - 5 V trigger pulses.

The specific VI I am working with right now, as a test of why mine are not working, is the 'AI Waveform Scan (scaled arrays)'. I want to get it to collect Channel 0 by triggering off of either Channel 1 or PFI0. I am only trying to collect 250 samples at 5 MS/second. Even when I try to collect 4 samples, it still gives me the 'AI Buffer Read' error.

Was there something else I needed to do in making the transition between the two machines? I don't see any indication that the board itself is damaged, but is there some configuration step that I needed to complete? Thanks for any insight you can provide.

TJR

[Tom_W_[DE]]

Hi TJR-

Your board is now supported under NI-DAQmx. I would suggest using the DAQmx driver over the Traditional DAQ driver because of its increased performance and ease of use in programming.

Two shipping examples that could meet your need come to mind:

First, for a pure digital start trigger you will find "Acq&Graph Voltage-Int Clk-Dig Start.vi" quite useful. This example performs a finite acquisition of user-specified length in response to either a rising- or falling-edge signal on the PFI0 trigger pin.

Second, for an analog interpretation of your digital signal that will allow for trigger level configuration you might find "Acq&Graph Voltage-Int Clk-Analog Start w Hyst.vi" useful. This example uses the PFI0 trigger line (or any analog input channel) to check for a user-specified voltage level and even includes support for analog hysteresis to avoid unintentional trigger assertions and deassertions by noise or jitter on the digital trigger signal itself.

Both of these examples can be found by opening LabVIEW and choosing Help>Find Examples from the menu bar. Then browse to the Hardware Input and Output>DAQmx>Analog Measurements>Voltage folder.

[TJR_741]

I have verified that the DAQmx VIs do work, but I would still prefer to use the traditional. I gave up on using Mac OS X so that we wouldn't have to rewrite everything for the DAQmx VIs. Do the Windows Tradiational DAQ VIs simply not work?

If anyone has experience, positive or negative, with the Tradiational DAQ, I would appreciate hearing it.

Thanks a lot.

TJR

[Tom_W_[DE]]

Hi TJR-

I was unclear on your motivation for using the Traditional DAQ instead of DAQmx. To answer your question, the Windows VIs for Traditional DAQ still feature full functionality and should work quite well.

To gain more insight into why the trigger settings might be a problem, I would suggest that you refer to this article: Pre-triggering on Multiple Channels or Triggering on Any Channel Other Than Zero (0) Causes Errors [link removed; article no longer available]. You may already be familiar with this operation, but basically the trigger channel must be the first channel in a list of sample channels (or the PFI0 trigger line) if you're performing analog triggered acquisition.

I have tested my card using the same VI you mentioned and various trigger levels with a 5V TTL pulse train. It triggers successfully when I sample the train as analog input channel 1 and use an analog trigger on the same channel. Can you check if this is successful on your card as well? Also, I am able to trigger on PFI0 with an analog rising edge trigger setting.

Please let me know if you're able to get the desired result with the method I have suggested here.

Thanks,