How do I program a NI 6602 card to send trigger pulses, one at each output port, triggered by an input trigger signal, using only one counter for each output port?

Question

Hello,
I have managed to program a NI 6602 card in LabView to send pulses on three different output ports, one pulse on each output port (with individually chosen delays) for each input trigger pulse coming on a separate input port. It is the DAQmx Create Channel (CO-Pulse Generation-Time)-VI that I have used for this, see attached code. However, this VI controls both pulse delay and pulse width, and therefore uses two counters for each output port (although you only specify one counter in the VI input signals), as I understand.
In my application though, I only need to have the delay chosen, the pulse width can be arbitrarily short, and thus I should only need one counter for each output port. How do I accomplish to program this in LabView?
Best regards,
Claes
Attachments:
Configure Side Camera Flash 1 Triggering.vi ‏47 KB

Answer 1

Well you're welcome to do that--it will work just fine as long as you are configuring a start trigger.
<rant>
However, personally I really don't like putting multiple counter outputs in the same task.  I have seen so many people assume that the counter outputs would be synchronized due to having them in the same task when this is not the case (you need to configure a start trigger in order to synchronize the counter outputs even if they are in the same task).  This is the only case I can think of where multiple channels in a DAQmx task are not automatically synchronized.
As an example:
Running this on my PCIe X Series gives a measured 2 edge separation of 1 ms + {7.78 us - 10.11 us}.  This would likely be much worse on a bus with more latency (e.g. USB).
The resulting output is close enough to what you might expect that it might go unnoticed, but really these counter outputs are not synchronized and it would be easy to glance at the code and not even think twice about it.  For the small amount of extra work on my end to create a separate task for each counter, it really clears up some ambiguity about what the counters are actually doing.  For me it's worth it.
So again, for your case there really isn't a problem with having the counters in the same task since you are using an external start trigger anyway.  I have just gotten in the habit of avoiding doing this.
</rant>
Best Regards,
John Passiak