Modbus Labview limitations

[jsasi]

Our system runs Labview v6.1/C++. In the grand scheme of things, our system will be a MODBUS (RS-485) slave device. I wanted to know what was the best way to send labview variables across MODBUS to the master device. I saw the Labview MODBUS VI. We have about 300 data points that will be sent to the master device. My main questions are:

- Is there a limitation for information that is being sent (ie. number of holding registers that can be read simultaneously etc)

- If this VI wont do it, what is an alternate solution?

- The master device doesn't run labview, they probably ping for data in some custom written code (still would use MODBUS commands). Can Labview send information when pinged by a system that doesnt run labview? In other words, would Labview with this VI (or any other solution) respond to a MODBUS request command to the serial port irrespective of its source?

A response would be highly appreciated. Thanks a lot in advance.  

[K C]

Hi,

The limitation is most of the time the programmer not LV.    (wisdom from own experience)

 

If the ModBus library has a limitation for your application then you can always modify it or write your own dedicated ModBus program. The last I did for our ModBus modules with non standard commands.

300 point is can not be a problem.

A ModBus slave programmed with LV is just a ModBus slave. It will answer to a ModBus master regardless in what language it is made.

 

So if the ModBus library is not sufficient for you have to wire same code yourself.

[JB]

There was (is ?) an error in the library that causes a limitation. Please see the readers comments on this page for more details.