Sending Strings over Modbus TCP to a V560 PLC

[LeonMötter]

So i am currently looking in to the possibility off sending strings (probably between 20 and 32 characters) to a v560 plc over modbus TCP. The purpose of the string is product name/version that is going to be produced on the machine where the v560 is installed. So the operator can easily sees if the right parameters are loaded. currently we do this with a 7 to 10 digit number but a mistake is easily made.

How i am thinking of achieving this is by converting the string to ASCII and writing it to 16 integers. Then in theory i could use ASCII string variable to display the name on the HMI.

For the moment i dont see any problems with the setup, but before i start writing the program i thought i might be smart to ask around here for other opinions. maybe there is a smarter way to do this?

[Flex727]

10 minutes ago, LeonMötter said:

For the moment i dont see any problems with the setup, but before i start writing the program i thought i might be smart to ask around here for other opinions. maybe there is a smarter way to do this?

Frankly, I don't see any other way to do this that wouldn't be overly complex. This is exactly what I'd do.

[Ausman]

To me it depends on what is harder to implement overall.  If the numbers always remain the same you could have a database in the plc that matches numbers to the visual description you want, and then displays that instead.  But if the numbers change all the time, then you need to do as described.

cheers, Aus

[LeonMötter]

Thanks for the input,

@Ausman, the numbers always stay the same, but new ones are constantly added. that is the reason we have a external database (SQL server) that can send recipes to each production machine. There are 11 production machines so keeping some sort of an internal database in each of them is probably not the best idea. Still Thanks for the reply.

[Fernando Castro]

I think it will be easier over TCP or UDP, you could send the ascii characters as string and the PLC will be able to read it as it is, I kind of did that while trying to implwment a FTP client on a v570, i could retrive the folder and file names.

However Modbus  its ok, but it deppends on how easy it will be for you to work on the database/computer side, you maye need to rearrange the bytes because of the endianess and also you need to set the specific modbus addreses. I did the other way arround ASCII string stored on the PLC to database over modbus TCP, and was tricy because my client (PC) had a slightly different implementation for de modbus protocol, and I did not had a way to combine the different MIs to a single string, best i could do was hex values, and at the end I needed to learn new programming languages and how to re compile the Database software (which is open source) just to add one custom function to convert everything into a human readable string.

 

over TCP its just sending the message to an specific port and socket, the PLC has a function block for reading the protocol as ASCII 

[Fernando Castro]

On 9/1/2022 at 10:05 AM, Flex727 said:

Frankly, I don't see any other way to do this that wouldn't be overly complex. This is exactly what I'd do.

 

I'll just leave this over here...

 

PLC:

Just 2 function blocks required on the PLC Socket Init and UDP_RAW scan (In theory should be the same over TCP, UDP was easier to implement required fewer things)

 

PC:

I'm using Node-Red and just send a "payload" containing the string "Hello world" using the UDP node :

udp out

This node sends msg.payload to the designated UDP host and port. Supports multicast.

 

And that was it. It took me 5 minutes no ASCII string conversion no data splitting, no byte re arrangement. just send a pure string as it was written.

Of course LeonMötter  It will be easy as easy it is from your the other end to get that string to an specific port and socket