How to make PFI to go high-to-low with sample clock?

[ykhan]

Hi everyone!

I am very new to LabView and I am trying to do something very simple in NI PCI-6534 and yet not getting anywhere (or not sure if that's the limitation of hardware)

My application is to acquire 2 channel (16-bit each) digital data from our custom designed Analog-to-Digital board.

So far, I am able to acquire finite amount of digital sample (say 100000) and using a start trigger (PFI6) to start acquisition from our custom PCB board. Just so you know that I am feeding the PCI-6534 a 20 MHz external clock through PFI2.

However, I would like to send a trigger/acknowledgement signal (low-high/rising edge) back to our custom board saying it's done acquisition of 100000-sample.

My problem is that whenever I am trying to use any of the PFI signal lines with a internal sample-clock, I am getting an error saying I cannot use PFI lines with any sample clock. But my objective is to use a rising edge (low-high) to trigger back.

So far, I can pull the PFI4 high and used a timer to make it low. But the resolution of timer is milliseconds range (software based). I would like to have at least in some microseconds.

I also tried using implicit since Manual says it doesn't require any clock but still not getting result. Also, I couldn't find any example using implicit clock and not sure if PCI-6534 supports it.

Note that I am able to use sample-clock timing with any other DIO (Port 0 to Port 3) lines and get the result I am expecting. However, I would need to use all the 32-DIO lines for Analog-to-Digital data from our custom board. So using PFI line for acknowledgement is the only choice.

If you guys have any ideas/pointers, please throw them at me, I will try them out. Thanks a lot for your help! 🙂

Cheers,
Yaseen Khan

[Dustin_D]

Hi yhan,

You can try using the DAQmx Export Signal VI, with this you should be able to export your clock out to a PFI line.

Hope this helps!

[Dustin_D · Accepted solution]

Hi ykhan,

I noticed after posting that this will not really work for what you are trying to do.  The PFI lines on your 6534 are static I/O only as shown in the DAQmx help.

 You'll be able to control these lines, but only with software timing.  You should be able to call and assert them by their Physical Channel Name.  I hope this helps!

Regards,