Plc to Labview tcp/ip communication

[ramprabhakar26]

thanks for link dave, why is this method preffered than I/o servers 

[Dave_Brandt]

For me, I like it because it can be in your Vi or a plug in vi. If in the same Vi, you can have the communication loop and the code loop in your vi. You do not have to worry about deploying an I/O Server, making sure it is started and if it is communicating. I can also control how it handles communication failure and control values when communication fails. I used the I/O servers when NI first started using them (labview 8.0 I think) and there were bugs. I am sure they work better now. So for these reasons I choose to use the Modbus library VIs. The  examples in the library can easily test your plc connectivity without creating an IO server. .

[Dave_Brandt]

The only disadvantage using the Vi library as opposed to the I/O server is you have to format real and 32 bit data from 16 bit data. Modbus data is stored in 16 bit register's and bits (coils). So you have to format the data into the correct data type (2 registers for a real or 32 bit Integers data) The I/O server does this for you.

[ramprabhakar26]

hi dave 

i remeber you have sent me a link yesterday and im afraid those links are not working.and do you have example vi of your program so that i can understand what it is even clearly

thanks

[ramprabhakar26]

hello dave 

first of all i would like to thank you for your help this method is very convenient than i/o servers 

but im having problems with write to coil can you help me with that

[GokulGKM]

hi,

        you can download directly modbus libray based on which labview version your using.ther have lot of examples.like this link .

          http://www.ni.com/example/29756/en/ 

[ramprabhakar26]

hi gokul 

thanks for the reply i have one final uestion to ask im an applications engineer can i use these modbus libraries in my projects will it cause any problem

[GokulGKM]

hi,

       problem means what kind of you think.use no issues.