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No explicit path exists between the two channels

Hello,

 

I am developing an automated harness tester for automotive applications. We had a working program using one switch card, but capability needed expanding and a second card was added. Previously our program had LabView modules written using NISWITCH blocks, but when the second switch was added I had to recreate these modules using SWITCH EXECUTIVE blocks to properly handle using a virtual device containing both switches. When running the test after these changes, everything seemed to be working well, until I get to a certain point.

 

During the test I receive the error "No explicit path exists between the two channels". This happens, repeatedly, when I try to connect r1 to c65,c66,c67,...,.... This happens a few dozen loops into the test, so it seems as if the overall architecture is working, just not past this point.

 

In TestStand, the error is reported as coming from niSE Find Route.vi, stating No explicit path exists between the two channels. Path Capability is returning as (1) which looks to be "Path is available", so I am confused why this error is coming up, and how to correct it.

 

I am able to set a route r1->c65 in MAX and MAX says the route configuration is valid.

 

I have made a standalone LV program to manually check and connect routes. I am able to create a DMM measurement route ([positive post] r0->c1 and [negative post] r1->c2, to take a resistance value between c1 and c2, for example) that contains the leg r1->c65, and the route is able to connect and take the measurement, leading to more confusion why I am seeing this error in TestStand.

 

Any ideas?

 

I have attached the configuration for the virtual device in question.

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StevoP80, 

This is an interesting issue, and I appreciate the debugging trouble you have gone through. Your validations have led me to think the issue lies with how TestStand is handling the configurations between iterations. I am digging further into this, and just wanted to give you that update. It will also help to know a bit more info: 

-Does the error occur at the same iteration of testing each time?
-Is it consistently the same selection of columns that you cannot connect to?

-Does it only occur with r1?

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Thanks for the reply t@nim@t0R.

 

You first assumption was also mine. It almost seems as if TS is not getting the 4x128 topology designation assigned to the switches in the virtual device.

 

Yes, the error occurs when connecting channel 65 or greater to r1, every single time.

Yes, it is consistently channel 65 or greater, never any issues with channels less than 65.

I have not tried to reverse the order of the connections, let me try this and update later.

 

Another thing I tried was removing the steps that imported the netslist from excel, and removed the automation loops that stepped through these connections and indexed the array of nets as it went. I then assigned static values to rows and columns to connect on the connect/disconnect steps, including channel 65 and greater, and TS was able to connect these routes and take a DMM measurement with no issue. But add in the automation loops, and the imported excel file, and the issue is back. 

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I would also like to let you know that I have a thread on the TestStand forum as well. This board is rather slow and was't sure how much help I would get in here. Also, I am still unsure if the issue resides with Switch Executive, or with TestStand.

 

Here is the link to the other thread, which also contains attachments of my TS sequence, LV files for importing the netslist from excel, as well as my LV sub-vi's using niSE to connect the routes in TS. Included with my LV sub-vi's to connect routes is a standalone little LV test using these same sub-vi's, and is able to make connections to channels 65+ with no issues. Also there is a sample netslist excel file used during troubleshooting.

 

http://forums.ni.com/t5/NI-TestStand/No-explicit-path-exists-between-the-two-channels/td-p/3584157

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Update:

 

I created a netslist starting with channel 60, through channel 128.

 

The TS program was able to connect to channel 65 in this instance. The error occurred on the 65th iteration of the automation loop, so in this case channel 124.

 

This leads me to believe the issue is in TestStand, specifically with the automation loops. This worked previously however, when the LV sub-vi's used NI Switch, instead of niSE. Still confused about the true cause.

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StevoP80, 

Yes, I am actually collaborating with my colleague who is working with you on the other forum; for information organizational purposes, it will be best if you continue posting to the TestStand forum. We are both looking over the information and collaborating to understand what is going on. 

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