DIO Read Hangs with Triggered Input

[jdkoola]

LabVIEW 6
NIDAQ 6.6
DAQCard DIO-24
MacOS 9.x

I am using low level VIs to perform Digital Reads from a single line with a hardware trigger. On a separate port, I am performing software-start digital output.

The VI sporadically hangs. This problem seems to have popped up ever since we started getting high-frequency noise on our trigger line (unfortunately we can not rectify this problem as it is out of our control). When the VI hangs, often times the computer itself will freeze. I've tried changing sampling rates, etc. I've set it to allow buffer overwrites. Essentially I am trying to use the DIO Read as a sort of event counter (since the DIO-24 does not come with a GPCTR). For this purpose, I sit in a loop trying to
read one sample from the DIO Line (which will of course fail until I receive a trigger signal). Once I am able to read a sample, I call BufferControl with a code of "start" to restart the triggered operation on the DIO Line.

Any help would be greatly appreciated.

Regards,

Jejo Koola

[jdkoola]

*EDIT*
It's a DAQCard 6533 not a DIO-24

[rgharrison]

Hi Jejo,

Have you tried running the shipping examples with LabVIEW to see if it hangs? It could be a problem with the computer and not the noise on the digital line. Typically, the DAQ boards are fairly immune to noise on the line. It will either register as high or low (depending on the value and the noise).

From what I understand, you want to wait until you receive a certain number of digital events on the digital line. Once you receive enough signals, you perform a digital start for the second operation.

One approach, if you are only looking for a digital trigger signal, is to use the digital trigger signal on the ACKTRIG1 line and start your operation when this line goes high (or low).

Another approach is to use Change Detection on the dig
ital line you are monitoring. Once the change detection detects a change it will grab the data from whatever port you want.

Acquiring Digital Data Using Change Detection
http://sine.ni.com/apps/we/niepd_web_display.DISPLAY_EPD4?p_guid=B45EACE3DE7F56A4E034080020E74861&p_node=DZ52318&p_submitted=N&p_rank=&p_answer=&p_source=External

My main suggestion is to try running sample code that does almost what you are looking for and see if it still crashes or hangs.

Ron
Applications Engineer
National Instruments