Reduction in Jitter and Prevention of Data Saving

[GeraC80]

Hello, 

We are using a MyRio with FPGA and Real-Time Measurement toolboxes. The MyRio acts as a slave to an external microprocessor Master, and they communicate over SPI. I have been able to get the two communicating successfully, but when I pass the data from the timed loop to a lower priority loop I get jitter, and for some reason, the express VI will not save the data. I am at a loss as to what I can do to fix this as I have switched from a normal loop to a timed loop, used buffering and anything else I can think of but I still get the jitter and still it won't save the data. Any constructive feedback and suggestions on how to solve this issue would be welcome. 

[crossrulz]

1. You really should be using a DMA FIFO to pass the read value from the FPGA to the RT system.  This will become a lossless communication path and you can log all of the data.

2. Your myRIO is its own computer.  It cannot save directly to your PC's hard drive.  You can make another application that runs on your PC to get readings from the myRIO (use Network Streams to be the simplest).  Or you can save the data directly on the myRIO and then use WebDAV or FTP to get the data later.

If you really want to read up on how to do this: NI LabVIEW for CompactRIO Developer's Guide