I am using the 7831R FPGA board. I trying to run one of the
example VIs to see if my system is functioning properly. The Vi is the
AI-single. It is supposed to monitor one analog input. When I open
Labview, I choose the PCI-7831 device as the target. When I run the VI,
it asks me to compile it, and it takes a minute and compiles. Then I
switch the targets on the device emulator to Labview for Windows as
this creates the host VI, is this right? When I run the VI, I get
something like a rondom number generator, with values up to tens of
thousands. I set the min and maximum values to -4 and 4 , and then the
values stay under 120-ish, but still do not make sense. Did I install
my hardware/software right? Because when I was installing it there was
an error with NI-watchdod 2.1 installation. Is this important? Thanks
much, my head hurts.
The 7831R doesn't use watchdog timers, so the NI-Watchdog install problem shouldn't affect your application. A re-install of the drivers might take care of it though.
As for your example, you did all the correct steps leading up to running the example. After "AI-Single.vi" compiles and downloads to the FPGA, just keep it targetted to the PCI-7831R in order to run it, instead of targetting back to LabVIEW for Windows. This is actually taking real-world values, so if nothing is connected to your device the signal will be floating. (Note: this does not make use of a Host VI)
If you want to use a Host VI architecture, you are correct in that you will have to then change the target back to LabVIEW for Windows. To better understand this type of application, take a look at the shipping examples "Synchronization - Polling (FPGA)" and "Synchronization - Polling (Host)". You'll notice that all the Host VI does is call an Open VI Reference (which opens and runs the pre-compiled FPGA application, "Synchronization - Polling (FPGA)" ), and then uses Read/Write Controls to pass data back and forth from the Host to the FPGA.