polling variables using Modbus IP and labview 8.2.0 shared variables

[RavensFan]

One thing that is interesting is that NI has the word "nonexistant" spelled wrong!.  Its correct spelling is "nonexistent".

Message Edited by Ravens Fan on 01-04-2008 01:26 PM

[Jennifer_R]

Hi richjoh,

I noticed there is now a Device Status shared variable.  Has that provided any insight as to why you may be receiving a device error?  A good first step when receiving error -1950679038 is to check your hardware configuration.  

I'm not sure about the Commfails.  Do you have any waits in the loop you are running?  Also, do you have multiple network cards on your computer?  If so, it may help to disable any that are not being used. 

[richjoh]

Jennifer,

I create new modbus servers, a master (the Watlow controller) and a slave server. I see the values are updated for the master, looking at this through the SV manager.

My problem is whenever I run a vi with a SV control or indicator I do not get update. What need to be done here to ensure I update controls. Apparently the modbus is working from the attached pic of the SV manager...

richjoh

[richjoh]

OK, SV on the block must be wired or errors occur.

I can read registers and write, my problem is when I make a value change on a control, the SV green (triangle binding  indicator) goes red! At this point I see the SV engine is running but SV manager reports "device failure". I can only read my value back after I toggle the SV engine process off  and back on. What going on here...anyone???

[richjoh]

OK, just to clear this issue up a little, I confirmed the following.

LV version 8.2 DSC modbus is not functional after a write. All shared variables show device error in the manager after a write. Only a toggle of the process will bring the SV back.

LV version 8.5 DSC modbus is functional after a write. My Watlow controller is capable of update at 100msec. LV version 8.5 Modbus default update rate is 1 second. Writes require a few seconds to read back in LV 8.5 modbus. During the time between writes and read an error is reported in the error cluster (block diagaram SV) or you get the red icon (front panel SV).

Thus issues still exist with Modbus SV engine LV 8.5

richjoh