Generate trigger for data acquistion at both falling and rising edge, recommendation on devices/functions?

[Mr.Nobody]

I have an external pulse generated from a motion controller in the format of square wave.  And I need to send a rising edge signal to another device to acquire data at each bit-flipping point (so both rising and falling edges of that external signal) so that my data acuquisition is synced with the motion control. All those signals I'm referring to will not be at very high frequencies.

Is it possible to use some kind of device to achieve this? I currently do not have any DAQ board installed in the PC. Thanks a lot.

[lis@jiang]

Hello,

From your description, it seems like you need a device that has digital in and digital out.  Feel free to get in touch with your local sales representative if you have more specifications.

Thanks,

Lisa

[John_P1]

You can do this with a DAQ device that supports hardware-timed change detection (like most M Series, all X Series, and 2nd generation CompactDAQ).  Basically you need to configure a Digital Input change detection task sampled off of the rising and falling edge of your external signal.  Then, export the change detection event to an available PFI line.

I suppose the lowest cost solution that NI has to offer would be a 9171 carrier with a bidirectional DIO module like the 9401 or 9402.

Alternatively, if you want a device with other functionality you might look into an X Series (e.g. PCIe-6320).

Best Regards,

[Mr.Nobody]

Thanks so much for the replies.

I did some research online and found this KB: http://digital.ni.com/public.nsf/allkb/5A2DC5CF7246E08386256B79006279BC 

It suggested something different, such as E series, 660X series etc.  So which should I choose?

Another update on that external signal I was referring to:  actually I would be able to configure two outputs on the motion controller to output opposite phase pulses simultaneously (101010 and 010101), so I would be able to have a rising edge at each location as long as I could use some device to sorta "combine" two pulses.  Is it better than using one pulse?

[John_P1]

Oh wow, that KB is quite old (last updated in 2004) and doesn't mention the newer hardware that also supports change detection (other than the 653x).  Here's a list of some products that support change detection which I would recommend (we'll have to update the KB to include more recent hardware):

USB:

USB 9171 + NI 9401 / NI 9402 (depending if you want BNC or screw terminal connectivity).  The 9171 could also be replaced with a 9181 or 9191 if you want ethernet or wireless instead of USB.

USB-6341 (more expensive, but gives you AI and AO functionality as well as more digital lines).

PCI/PCIe:

PCI-6220

PCIe-6320

Both E Series and 660x require an external OR gate to implement what you need--and E Series devices are quite a bit more costly than the equivalent M or X Series since they use legacy components.  You'll end up with more features for less cost if you go with one of the above options.

With change detection you can generate an event on rising or falling edges on multiple lines, so there isn't really any difference between triggering off of a single line's rising/falling edge, or triggering off of the rising edge of two different lines. 

Best Regards,