I need to make multiple simultaneous calls to DAQmx Write. This works for the first 7 calls, kind of works for the 8th call, but never manages to make a ninth call.
I have a NI PXIe-1065 chassis with 11 NI PXI-4461 cards. The embedded controller is a PXIe-8133, with an i7 Q820 processor and 8GB RAM. I am writing the code with LabVIEW 12.0f3 and NI-DAQmx 9.6.1f1
I need to start and stop each of the PXI-4461 cards independently. I have a reenetrant vi that I call dynamically each time a card is started. That vi has a (reentrant) subvi that reads data out of its queue and sends it to the DAQmx Write function, also in that subvi.
This works fine with with 7 cards running. I can start the eighth card, but after doing so, everything in the rest of the program slows down, to the point where, for instance, a reference probe updates line by line. If I try to start up a ninth card, the process, which should take a few seconds, takes... well, I don't know how long it takes because I usually just stop it after a minute or two. CPU usage doesn't change during this (~23%), and neither does memory usage.
If I disable the DAQmx Write part of the code, the rest of the code works fine. I can call the parent reentrant vi all 11 times with no slow down in the code.
The data rate for all the channels is 32768 S/s. The data is read from TDMS files in 2 second chunks. I've set the WaitMode on the Write to "Yield", but that doesn't seem to help. I've played around with setting the output buffer size, but that doesn't help, either.
So, as the Subject says, is there a limit to the number of calls to DAQmx Write that can be made simultaneously? Or is there just something I'm not setting right?
Cat
