Modbus

[Donya]

Hi,

I am new to Labview and I am trying to write a code in Labview and I have the Modbus comminication protocal. I want to be able to send messeges through the labview code and ask the inverters, which is connected to PV modules, to give me data and it just send me back the data. this is going to be a RS 232 communication.

Where do I start? please let me know if you know anything about this.

Donya

[Dennis_Knutson]

Start here.

You'll have to decide whether you want to use DSC (an extra cost add-on) or the LabVIEW modbus library that is linked in the above tutorial. There have been numerous discussions on modbus. Search the forums and the NI Developer Zone.

[Donya]

Thank you

I will be studying this for a little while and see if I get any where.

[Donya]

Hi,

I need to put a code together that would allow me to have a serial communicatio between two computers.

I have started this by using instrument I/O and using the Serial tools.

I need help with hooking them up, I have no idea with one goes first, and I have been opening them and I found the options for parity and flow control and... in the configure serial port and I have no idea how to connect them to each other?!!

Thank you

Donya

[Donya]

Hi,

I need to put a code together that would allow me to have a serial communicatio between two computers.

I have started this by using instrument I/O and using the Serial tools.

I need help with hooking them up, I have no idea with one goes first, and I have been opening them and I found the options for parity and flow control and... in the configure serial port and I have no idea how to connect them to each other?!!

Thank you

Donya

[Bublina]

Try leaving everything in its default values for start.

[Dennis_Knutson · Accepted solution]

Both ends just need to be set the same. For the physical connection, you need a null modem cable (tx and rx swapped).

Why would anyone use serial for communication between 2 pc's instead of an ethernet connection?

[Donya]

Thats a little complicated, I want to test it by talking with two computers first and then I would be hooking it up to another dvice.

So I have all these Write function and Read function.... and I am not sure what I should be connecting to what?!!

[Donya]

What do you mean? I probably need to give it some values, I will eventually change the parity and start bit and stop bit,.... alll that but for now I need to know how to hook them up to eachother.

?!!

[Dennis_Knutson]

Your approach seems overly complicated and not guaranteed to help much with communicating to an actual instrument. You would need to write some custom code at one end that would emulate the instrument's response. You could do a simple write of anything you want at one end and simply read it at the other. All that you would need is one of the existing serial example programs. Since an instrument would have very specific commands and responses, the simple check would only verify that the com port on your pc is working. A simple loopback on one pc would do the same thing. The instrument you would use might not even use the same type of serial cable. I would suggest you not waste your time and start by verifying communication with a program such as Hyperterminal, Procomm, Putty, or MAX's VISA utility. Then see if there is an existing driver for it (Help>Find Instrument Drivers). Find out more about instrument communication and drivers here.