6008 trigger(s)

[dtnpsi]

Just got my (first) 6008 about a week ago. I plan to use DAQmx 8.0 in a .NET 1.1 app...

My app needs to get a notification when either of two digital inputs go high (basically, to log the time-of-day), but I don't want to have to "poll" the digital inputs in my app.

I assume this involves using a trigger.

But what constraints does the 6008 have regarding triggers?   I read that the PFI line can be used, but there's only one on the 6008. Can other digital input lines be used for triggers?  

Also, I've looked at the examples that use digital triggers, and the triggers are being added to the .Triggers collection of the Task object. But it's unclear to me what "type" of Task object I would create if all I want to do is wait for the trigger event... 

Any advice greatly appreciated.

David

[WM_John_Weeks]

What you're talking about is really an change event- your software runs when a change is detected on a digital input. The USB 6008/9 don't have that. The USB 6008/9 are quite limited. You get what you pay for 🙂

[dtnpsi]

So now I'm even more un-clear on what a "trigger" is (and isn't)... 

The documentation of the .NET classes of DAQmx sure makes it sound like all that's necessary in order to do "digital change detection" is for the DAQ device to have a PFI channel (and the 6008 has one). 

If the 6008 doesn't support digital change detection events, which USB-based NI DAQ devices DO support it?

Incorporation of a higher-end DAQ device in the system being developed would not be a problem.

Thanks,

David

[WM_John_Weeks]

Well, searching the NI site for "change detection" turned up this:

http://digital.ni.com/public.nsf/allkb/8914FA5E30971E0C86256FEF005760FF

But it doesn't list a USB device. Now that you know the NI-speak for what you need, you may want to talk to your sales rep.

As far as what "trigger" means, I would say that it is a (usually) hardware signal that can be used to control (usually start) a hardware operation like scanning the analog inputs, outputting an analog waveform, or reading/writing digital I/O ports. What you want is not the start an operation but to have your software notified of an event.

NI's use of the term "pause trigger" suggests that there is some fuzziness in exactly what a "trigger" is. This is why I said "usually start" above. What NI calls a pause trigger, I call a gate.

[Tom_W_[DE]]

Hi All-

John's link does in fact list the only NI devices that support change detection, and no USB devices are currently supported.  This sounds like a great product suggestion. 

Thanks-