Hello MBoyd,
To check- have you attempted deploying the benchmarking code linked via the aforementioned whitepaper? The link is at the end of the PXIe-8108 benchmark section, just in case here it is linked again:
As for other references, these documents may also be helpful:
NI-DAQmx Hardware-Timed Single Point Lateness Checking (not specifically what you're concerned with at the moment, but demonstrates quite a few options for HWTSP I/O)
https://www.ni.com/en/support/documentation/supplemental/21/ni-daqmx-hardware-timed-single-point-lat...
My impression is that this simultaneously-sampled card shouldn't see much of a hit when acquiring from all channels, and that well over 1 kHz should certainly be possible. It seems more likely that there is some sort of RT priority, transfer latency/read processing, or synchronization problem. Out of curiosity, how fast can you run a loop containing a simple software-timed read with a 1us wait timer (one of the SW Timed Input examples, but minimize the execution throttling/wait timer)? Obviously this isn't what your end goal is, but I'd still expect a rate of >1kHz.
A few other clarifying questions:
-What is your actual target loop rate?
-How many channels do you intend to acquire from, if possible?
-What do you mean when you say that polling mode didn't give you the required overhead to properly operate the circuit? As a note, polling in an otherwise uncontrolled loop will likely utilize whatever CPU cycles are available, however this is intended and accurately represents that the polling function is querying for an update as fast as possible until the event of interest has occurred. You should still be able to perform your processing and AO before beginning to poll, with the caveat that your maximum loop time still needs to be less than the single-point sample period.
-Have you attempted using a timed loop synchronized to the sample clock rather than the wait for sample clock function? This may be a viable option.
-Are you running this code interactively via the LabVIEW development environment (Click the VI's run button while targeting the RT Controller) or deploying it as a Real-Time executable? Interactive execution will almost certainly slow things down quite a bit.
-You indicated that a Read is the only function in your primary loop- are you using the Wait until next sample clock function or the Report Missed Samples property?
It would also be helpful if you could post the actual code you're using, if possible- there are often small things that are much, much easier to pick up on when you can see the code.
I'd also recommend getting in touch with NI tech support directly if you can- this type of question is the sort of thing they handle regularly and they likely have additional resources to answer questions such as expected rates for your hardware/software configuration. Be sure to mention that you are looking for advice on acquisition times for the PXIe-4300 and reference this thread if/when you call or email support.
Best Regards,
Tom L.
