read variable from NI 9149

[Xiao@Gemini]

Hello everyone, I'm acquiring data from NI9149 using shared variable read function see figure below. This cause delayed execution of the timed loop than my main while loop since I have two expansion chassis, total 16 slots. Is there any other function I can use to acquire data with NI9149?  I tried scanned variable read, it does not work. Thank you.

[Trevor.H]

Hey Xiao@Gemini,

What speed do you desire your loop to run at?  Additionally, have you considered a producer consumer architecture?

[Xiao@Gemini]

My data acquisition loop is running at 40Hz, I'm using scanned variable read for my cRIO 9035 and shared variable node for expansion 9149. I'm using queue function for data communication. When I click run, about two and half minutes later, the dequeue element function transfer data to calibration while loop. I do not know why. 

[Trevor.H]

Interesting.  Could you try pinging the 9149 to see how many ms a connection takes?  The ping should provide insight into whether there are networking delays causing this.

[Xiao@Gemini]

I have no idea how to measure that, can you provide more details? Thank you.

[Trevor.H]

You can ping an address by opening the command prompt (hit the windows button and type cmd) then typing "ping" followed by the IP address of your target.  This should return information on how long it takes to communicate a basic connection to the device over the internet.