LabVIEW Graphs Missing Data Followed by Double Data

[CamBAC]

Hello,

I have a test system that updates a graph anywhere from 40 - 200 times per minute. Occasionally and especially with the faster refresh rates, the graph will blank (not show anything) and then will show 2 waveforms together. It seems like the data gets backed up and then is all released at once. 

I have seen this on multiple different CPUs so I'm not sure it is a CPU issue. It also happens more consistently at the very start which may be a clue. 

The hardware I am using is a NI USB-7845R. 

Has anyone seen this before or know of any fixes?

Normal Graph

Double Graph

[Kyle97330]

We'd need to see code to help, not just screenshots of graphs.  Please post your VI (and any subVIs), saved as 2020 version or earlier, attached to your post.

Most likely you're making some sort of assumption about timing that isn't true, or have a race condition in your dataflow from local variables or something along those lines.

There's also a chance you're doing something like using trigger levels close enough to the noise level, so in addition to your VI files it would be helpful if you exported the data that goes into the graphs (two sets, one for a normal graph and one for a double).

[CamBAC]

The entire code is fairly involved and uses LabDogAPI for an OOP design (I am not the original author). Data is sent with messages around the program. This has caused timing issues before but I am not seeing one for this issue.   

That said I can trace the issue as far back as this module. This is the FIFO buffer in the FPGA where the data is collected. For some reason it is empty on the 1st pass. 

I tried extending the timeout to 10s but that didn't help. It is up and running within 10s so a longer timeout wouldn't help. 

Is there something with the FPGA that could be causing this?

Let me know if you want to see any other code around this or if there are any noticeable issues with this code.