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@brinkrob wrote:
I'm writting an application using a NI-6536 with NIDAQmx written in C++. What I want to do seems simple enough, but I'm having a hard time finding out how in the documentation or on these boards. And it may simply be that I am not familiar enough with the terminology involved.
I have two different things that I want to do.
I want to output 4 bytes of data, one byte at a time (each bit on its own line). The hardware I am talking to is designed in such a way that whenever it detects a falling edge on a strobe signal it latches the value of the 8 lines. So part of my problem is generating that strobe signal when my data is ready. I also don't want that signal to keep going when I dont have new data to send. (my data will come in bursts.)
Can I use Continuous Digital Output so that I do not have to hand hold the hardware through this procedure? Specifically, I'm curious how to output the Data Strobe. Is it as simple as using DAQmxExportSignal to export the SampleClock to PFI4? What will happen when the hardware is waiting for more data to send, is there a way to hold the outputs at whatever they were last, including the sampleclock?
In theory I could structure my data in such a way that the data strobe was actually part of my signal. Such that I output each byte of data twice, first with a strobe signal high, and another time with it low. In that case I wouldnt have to output any clock per se because It would be part of the data. I'd hate to use this implementation though if there is a simpler way.
My second problem is related to my first. In addition to outputing data, I also have to act as the reader in the same kind of scenariodescribed above. The only difference being that the strobe used to latch the data will be the very same strobe that I am outputing above. So its a strobe that I output rather than receive. Is there a way of accomplishing this short of having the hardware I talk to, route the strobe sugnal back to me on PFI5 and doing basic continuous digital input? For example, could I use DAQmxConnectTerms to route PFI4 to PFI5? (Assuming that in the above case my strobe signal is output in PFI4.)
I also find it wierd that there is truely only one PFI line that I can use as an input clock, and one that I can output a clock on. Is that truely the case?
Thanks for the Help
-Rob