Hi everyone. I'm decently versed in CAN from my years in automotive and robotics and I have a few years of LabVIEW development under my belt. I have a LabVIEW program that is sending out two separate CAN frames. The first vi uses an XNET Create Session set to Frame Out Stream, writes my CAN frame, clears the session then creates another session set to Frame In Stream and reads the streaming data for 15 seconds. It works great. The second vi partially works and uses a Create Session set to Frame Out Single-Point, writes my CAN frame, clears the session then creates another session set to Frame In Single-Point then reads that single-point data. I can see every message I transmit and the corresponding response on the XNET Bus Monitor. My single-point read is showing the correct frame ID but the payload data is all zeroes yet the bus monitor displays the exact data I should receive which is not zeroes. I'd appreciate any help I could get on this.

But you are still creating a read session, after performing the write for a request. It is possible that you send the request, then the device replies, then you create the read session, only to find nothing because it has already sent the reply. The read will only return stuff that has occurred since the creation of the session. What I was suggesting you do is create all of your sessions at once before ever performing a read or write. This could be outside of your loop entirely, or by using data flow to ensure both have started first. Then use those sessions in your loop as you need performing writes reads etc. Then outside of your loop once it stops running close all your sessions. Also in your code you currently aren't closing your write sessions.

Automotive and Embedded Networks

LabVIEW 2017 XNET CAN Read issue

Solved!

Hello,

did you find the root cause of why you are only able to read the signals with the bus monitor open?

Because I have a Labview RT 2015 based program running inside a PXI system and I am experiencing a very similar problem, in my case, if i run bus monitor only once and then stop it, then I am able to read the different signals.

Thanks