Modbus IO Server Issues Error -1967353902

[jdenn]

Good morning,

I am trying to communicate from a cRIO 9035 to a cRIO 9030 through Modbus and I keep getting error -1967353902 on the cRIO 9035.  I am using the NI 9871 modules on each cRIO.  I never get this error on the cRIO 9030, it is only on the cRIO 9035.

I found the following note when troubleshooting Modbus IO Servers: http://zone.ni.com/reference/en-XX/help/370715P-01/lvmve/dsc_modbus_trbsht/

I do sometimes get error -1967353900 which in that link states there is an issue with other devices occupying the serial port.  

I ended up creating a new project with just a simple vi to test the comms between the units (attached).  When I first started each vi, everything worked fine.  But subsequent launches, I get the error codes above.

Here is a list of things I've tried:

-deleting/creating new Modbus IO server

-verifying that opening a VISA terminal in NI Max that the ports are able to communicate

-reformated the cRIO-9035

-created a new project (attached) with simple library

I'm at a loss here as to what else I can try.  Does anyone have any suggestions?

[jdenn · Accepted solution]

I was able to figure out this problem.  It turns out that while testing, I loaded several Modbus libraries tied to the same Modbus server onto the cRIO.  I think the IO server didn't know which library to use so it threw an error.  This also explains why after I formatted the cRIO is work initially and then stopped working after I started to load more code onto it.

I resolved it by deleting the libraries from the cRIO in NI Distributed System Manager.  Once I deleted all libraries except the 1 under test, communications were restored.