MODBUS TCP on CODESYS

[boneless]

Hi all,
A couple of years ago, I ran some tests with MODBUS TCP communication between rPi running CodeSYS and a couple of Arduino's.
I remember that I could set all the parameters under the MODBUS devices.
I am now trying to run another test, and I can't seem to find where to set the IP address for my SLAVE/SERVER. Am I correct to assume that this is set through a FB now?
Nor am I able to find any free libraries on the CodeSYS site. Am I looking in the wrong place?
Any help would be greatly appreciated!

 

[kallileo]

Hi all,
A couple of years ago, I ran some tests with MODBUS TCP communication between rPi running CodeSYS and a couple of Arduino's.
I remember that I could set all the parameters under the MODBUS devices.
I am now trying to run another test, and I can't seem to find where to set the IP address for my SLAVE/SERVER. Am I correct to assume that this is set through a FB now?
Nor am I able to find any free libraries on the CodeSYS site. Am I looking in the wrong place?
Any help would be greatly appreciated!

Normally you set slave's IP address in the General Tab of the Modbus_TCP_Slave but I can set it code as well. I do it when I want to let the user changer slave IP from the HMI.

Look at part 3 of my old blog:

http://automationofthings.blogspot.com/2015/10/turn-your-raspberry-pi-into-plc-part-3.html

 

[boneless]

ahhhh, ffs, I forgot one level .


I added the ethernet interface, then added the slave.
But I need to add the ethernet interface, then add the master (me) and finally add the slave that connects to the master.


Thank you so much, your blog gave me the hint I needed! .


Do you happen to have any examples of setting the IP with code through the HMI tho?

 

[kallileo]

Take a look at the link below:

https://faq.codesys.com/display/CDSFAQ/Modbus+TCP+Slave:+Dynamic+Setting+of+the+IP+Address

 

[boneless]

you are the best, thank you so much!!!

 

[boneless]

Hello again,


Did some more testing, your tutorial has been very helpful, thank you Kallileo.


I have one follow-up. Do you know if it is possible to read the status of analog output signals? I can read digital in and outputs, as well as analog inputs and holding registers. But can't seem to find a way to read output registers, only individual coils.

 

[kallileo]

In Modbus, analog outputs are usually mapped to Holding Registers (16bit integers) because only HR can be both readable and writable using the respective HR function code.

It also possible that in order to write to analog output you need write to a HR but in order to read the same output you need to read an Input registers.
There are also devices that don't have discrete inputs and input registers at all but only coils and HRs for both read-only and read/write memory supporting only few Modbus function codes.
Always check the manual of the device as Modbus be could a real mess.

https://blog.softwaretoolbox.com/opc-modbus-function-codes