Sorry I am having to repost this as I dont see the previous post anywhere, and this is sort of urgent for me. Is there some kind of a well documented example on how to use the modbus library MB ethernet master slave VIs to read from a modbus TCP connection? I have a Watlow EZ Zone PM controller using Modbus TCP protocol, and i know which registers i want to read to and write from, but I am not so sure how to make the required changes in the master slave VI, specially in the event structures. Could some one help me out please? I basically want to read from register 360 and write to register 2160 for now.

[sharmishtha]

Sorry I am having to repost this as I dont see the previous post anywhere, and this is sort of urgent for me. Is there some kind of a well documented example on how to use the modbus library MB ethernet master slave VIs to read from a modbus TCP connection? I have a Watlow EZ Zone PM controller using Modbus TCP protocol, and i know which registers i want to read to and write from, but I am not so sure how to make the required changes in the master slave VI, specially in the event structures. Could some one help me out please? I basically want to read from register 360 and write to register 2160 for now.

[jyang72211]

I coded up something for you.  See attached.  Let me know if you have more questions.

Yik

[sharmishtha]

Thanks a lot. Where can I find the ReadWriteParameters.ctl VI that i am being asked for when I open your VI? Thanks so much again!

[jyang72211]

See the new version of the program, attached

Yik

[sharmishtha]

Thanks so much! That was very helpful.

[alphakokoro]

Hi jyang72211,

I'm trying to control the same controller via Modbus RTU. The only difference is my instrument's connection with PC is over RS-232 cable instead of TCP.  I replaced MB Ethernet RW with regular MB RW vi.  I was able to communicate with the controller.  However, I received the same output values of holding registers for index 0 and index 1.  I know that I would have an array of two 16 bit values from each register and I will have to convert that to a 32 floating point bit number to get the actual value of temperature.  I believe all of my serial settings are correct but I don't know how to get these two values (given they are correct) and put out the wanted temp.  Do you have any suggestion?

Thank you for your help

Tim

[RavensFan]

Take a look at the numeric/data manipulation palette.  There are functions on there like join number where it can take two U16 elements and join them into a U32 element.  Typecast is another function that can work.

[alphakokoro]

thanks for the tip Ravens Fan, I was able to find the join number function in the pallete but then I don't know how to go from there to get the temperature value.  I did some manually calculation from those values in array and convert them to hex then combine them in hi-lo order then convert it to 32 bit floating point then I would get the correct #. I' m not sure how to actually get it done in LabView. Do you have any suggestion?

Thanks

Tim

[alphakokoro]

Ok, I typecasted it and got the reading. THanks!