HMI UART - Comect to PLC - RS485

[sutto]

Guys, I need help connecting RS485 - Modbuss to a clp
I am a machine manufacturer and I use HMIs from other brands.
I have never connected a UART HMI, always conventional ones.
The ESTONE product is excellent, but communicating with them is extremely difficult.
How is Modbuss addressing in the HMI? How do I address the entire system?
Thanks

 

[Harald Kapp]

More details, please.
Make and model, datasheet excerpt showing the interface conenctions. For both plc and hmi, please.

 

[sutto]

TKS Harald
the HMI is a STWI070W the PLC is a Siemens, communication will be via RS485 - Modbuss
Basically, I can't find the HMI where the addressing is carried out anywhere.

 

[Harald Kapp]

Looks like the HMI is not Modbus capable. There is no reference to Modbus in the manual. It is obviously meant to be controlled via a dedicated command set as described in the 2nd PDF you supplied.
Unless you are able to program the PLC to issue these commands and understand the reply, there is little chance you can use this HMI with this PLC.

 

[sutto]

I got this information from the manufacturer
I work with HMI made for PLC,I have never worked with one UART

Our development is based on UART.
1.Make pictures with drawing software.
2.Create projects with our software, adopts the direct variable- driven display mode.
3.Displays and operations are based on the pre- set variable configuration files. Thus, the software architecture is simpler and secondary development is easier.
4.Download the project to the display and Debug.
5.The MCU writes the code according to the protocol.
All in all, 0 code UI development.

 

[bertus]

Hello,

Perhaps someone on control.com might know more:

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That is our partner forum for automation.

Bertus

 

[sutto]

tks for your help !!!

 

[Harald Kapp]

I work with HMI made for PLC,I have never worked with one UART

You're mixing concepts:

• Modbus is a protocol. A set of defined commands and messages that allows interfacing different components independent of teh manufacturer (more or less). Modbus can be used on different media, e.g. Ethernet (Modbus TCP) or RS485.
• A UART is a hardware interface for serial protocols. A UART can be used to communicate via e.g. RS232, RS485 etc. WHt protocol is used over the UART interface is a completely different matter.
  When Modbus is used over RS485, then typically a UART is used to manage the hardware side of the interface, plus so called "transceivers" which handle the RS485 voltage levels (which are completely different from the logic levels a typical UART would use).

In your case the PLC obviously uses MODbus over RS485, which means there is a UART on the PLC side plus the above mentioned transceivers plus software running on the PLC that handles the Modbus protocol. Interfacing with this requires the other device (here the HMI) to also have the same physical interface (RS485) and the software to handle the Modbus protocol.
I may be wrong, but as far as I understand the STWI070Whas a protocol of its own which is not Modbus. Therefore you will not be able to establish communication between this HMI and the PLC using Modbus.
From the datasheet, chapter 1.5:

1.5 Working Principle The Intelligent TFT-LCD Module communicates with the Customer’s MCU / CPU / FPGA / PLC via Commands (JSON command and HEX Code), and thenthe MCU would control its connected equipment to work according to the received commands.

(emphasis by me). You may be able to coax the PLC to work with this HMI by writing your own interface software for teh PLC such that the PLC can create/send and receive/understand the commands and data according to the HMI's own protocol, but that is far from a no-code solution.