PLC MODBUS communication

hi, so anyone know how to connect a haiwell HMI with XINJE PLC by using MODBUS communication protocol? please help me ASAP. thank you

You will be hard pressed to find anyone using either of those I am afraid. Good luck.

reply to BOB

hi BOB, thank you for the reply, have you ever worked with two different kinds of HMI and PLC where serial communication doesn't support.

Modbus Generalities

This is a general comment that is not specific to your situation.

A common mistake for someone implementing Modbus is not having some understanding of Modbus FIRST. This may mean studying the Modbus spec. Us older types have a printed 'Modicon Modbus Protocol Reference Guide' PI-MBUS-300 Rev J (1996). I'm sure the Modbus association people have an online equivalent. You need to have an understanding of the different function codes. There's about 24 of them - you can completely ignore the majority. Most work can be done with just 3 and 16. The next ones to understand are 1 and 15. 2, 4, 5, and 6 are the last place that most people need to go.

The PLC class outline at CorsairHMI.com has some Modbus material including some discussion of the 1-register address offset issue that seems to plague most first-time Modbus users. It also has some discussion of the double-integer and floating point considerations. There seems to be a lot of other (and better) available guides to the topic. Chipkin Automation Systems 'Modbus for Field Technicians' by Peter Chipkin is a good resource and much better than anything that I have written.

I'm sure that there are plenty of people that love or hate Modbus with valid reasons but it's not going away any time soon. It may outline us all.

'Outlive' us all

As a basic consideration, the HMI is usually a Modbus master/client, for the sole reason that Modbus is a master/slave protocol and slaves are silent unless spoken to. If the state of a selector switch is changed on the HMI, it's up to the HMI, as a Modbus master, to write that change to the PLC.



If the PLC were the master it would have to continuously poll/read dozens/hundreds of status words looking for a state change on the HMI.

Basically

- You will have, in the PLC manuals, to learn how to configure Modbus and see which Modbus addresses correspond to the bits and registers that you want to manage on the HMI.

- You will have to make the physical connection between PLC and HMI. If it is Modbus RTU you will need to consult the manual of both and obtain or manufacture the appropriate serial cable. If it is Modbus TCP, both devices must be connected via ethernet on the same subnet and you must assign IP addresses.

- You will have to configure the HMI to connect as a master to the PLC and create the screens to display or modify the bits and registers Modbus addresses of the first point.

I have used Xinje PLCs but only with Xinje HMIs. The HMIs are pretty cheap and the software is free, it would be the easiest way forward.

the_msp said:

I have used Xinje PLCs but only with Xinje HMIs. The HMIs are pretty cheap and the software is free, it would be the easiest way forward.

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HI PLEAS CAN YOU HELP TO CONNECT MY XINJE PLC WITH MY XINJE HMI TGM 765 ET

ayesh said:

hi, so anyone know how to connect a haiwell HMI with XINJE PLC by using MODBUS communication protocol? please help me ASAP. thank you

Click to expand...

This is a very common problem, we would see this very frequently at Schneider Electric.

Modbus RTU or TCP? (or surprise the heck out of me and pick ASCII)

If it's going to be Modbus TCP (or whatever AdHMI supports), I would recommend getting the Free & Fantastic AdvancedHMI ("AdHMI") and using it as a "translator" or "go between" between the Haiwell and the XINJE. Once you get both sides talking the same dialect of Modbus you can remove the AdHMI "node".

The initial intent would be to have one network that consists of the PLC to AdHMI, and a second network of AdHMI to the HMI and let AdHMI pass the data (with any required modifications) between the two nodes.

This way you can debug each side without having to fix everything at once.

You also can do this using other free or commercial tools.