Modbus questions (using Unidrive SP and compactRIO)

[jdosher]

I'm working on a new VI for a compactRIO in which I've added a Labview Modbus Master in order to comunicate with an Emerson Unidrive SP.  I've set up a modbus bound variables library which contains the modbus I/O server. The first parameter I setup was reading DC bus voltage (400505), and that was being properly displayed in the GUI. All good.  Next I added a boolean and a GUI button for drive enable (400615) and RPM set command (400024).  The drive enable works properly, and I can vary the RPM with a slider attached to RPM set point and have the drive RPM change. All good. Kind of...

After adding these other items the DC bus voltage is no longer displaying anything but zero. I made no other changes to the VI or  the library excpet for adding the above two items. Is there something fundamental about modbus or labview's modbus function I'm not understanding?

In trying to figure this out I've added other variables which are also reading zero. I removed the DC bus voltage varaible from my libarary, then added it back in, and still no luck. Incedentally, I am getting RPM readout (400010) though. 

What am I doing wrong?

[jdosher]

I figured it out, so I thought I'd post a response in case anyone finds it useful in the future.

The solution was to create a range of variables. For instance, starting with address 400501, create 40 items. I was creating individual variables and that seemed to be causing issues.

[cyongjed]

Hi Jesse,

Do you mind sharing your VI that you created? I am currently working on a Unidrive M series for Read/ Write Operations for Final Year Project.