Problem of communication with compactrio

Question

Hello,
I am working with a compactrio 9014 and labview 8.5
I have a problem of communication with my compactrio. I acquire sound with NI 9215 and transmit points from the fpga VI to the VI on the real time target at a rate of 10Khz. On the VI on the RT I have two loops, one determinisic running at a speed of 10Khz (0.1ms) (in this loop I will do my signal processing) and one non-deterministic running much slower (20ms) to communicate data to my computer. To communicate data to my PC, I used shared variable.
The problem is that if I run the VI_RT, I loose immidiately the connection. I think that is because the VI is taking up all of the execution time of the
processor and is starving out the communication loop that is used to
send data back to my PC.
Because of this problem, I try to configure my compactrio to automatically run on startup of my cRIO. So I follow the steps I have read in another message in the forum posted by MattP
To make your application (RT host VI and FPGA VI) run automatically on startup of your cRIO, you will need to do the following:
1.  Download the FPGA VI to the flash memory on your cRIO.  If
using LabVIEW 8, right-click on the VI in the Project Explorer Window
and select Download VI or Attributes to Flash Memory...
2.  Build an executable out of the RT VI.  Under your RT target 
in the Project Explorer, right-click on Build Specifications and select
New>>Real-Time Application.  Select the source files necessary
for your application and any support files to be included.  Click Build.
3.. After building the RT Application, you will find its entry
under the Build Specifications folder in your project.  Right-click on
the application and choose Set as startup.  Right-click again and
choose Deploy, which will download the application to your cRIO.
With  this procedure, I thougt that I can  run my  loop faster  because I  don't have the RT VI open on my desktop  (PC), so the PC don't have to synchronise the VI. But when I startup my compactrio, I loose connection with the target...
So, what is wrong with my project?  Is it possible to run a loop at 10kHz on the real time processor and communicate in the same time (but every 20ms) data to my PC. Can someone explain me the right procedure to do that at this frequencies?
I have attached my project and hope that someone can help me.
Attachments:
Communication.zip ‏658 KB

Answer 1

Hello,
The method you use in your application to transfer the data from the FPGA to
the RT Host use the Front Panel Interactive Communication that write/read the
control/indicators of the FPGA VI. This method provides also risk of Race
Condition and use uP resources.
To avoid errors in data caused by race conditions and use less processor resources, 
I suggest you to rewrite this part of your application with the method 
DMA transfer from FPGA to Host.
You will find some good tutorial at the following address.
What
is the Best Method For Synchronizing a LabVIEW FPGA and a Host Interface VI?
Best Regards,
Nick_CH