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Example VIs produce random numbers
GreggCz
Member
07-03-2005 03:15 PM
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Hi,
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.
Gregg
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.
Gregg
Jeff M
NI Employee (retired)
07-07-2005 09:13 PM
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Hi Gregg,
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.
Let me know if you have anymore questions.
Jeff M.
Applications Engineering
National Instruments
