How to read / write to multiple Modbus RTU slave devices

EasyBuilder Pro Q&A
How to read / write to multiple Modbus RTU slave devices
none 0.0 0
1
  • HMI Model:cMT-SVRX-820
  • EasyBuilder Pro Version:6.10

Hello,

I am using a HMI cMT-SVRX-820 and i want to control 10 different Dixell thermo controllers modules , each having a different slave address ( 1 to 10) using MODBUS-RTU COM2 RS485-2W and connected on the same bus.

Let’s start with an easy function: Modbus zero addressing , coil 0x address 512 will turn ON and OFF the Dixell controller.

I want to create an interface with 10 switch buttons - one button for each device, that it will turn ON/OFF for each controller.

How can i do that in EasyBuilder Pro 6.10. ?

Thank you for your support and guidance.

2

Hello

Yes of course, you can use # before address as follow:

ID 1: 0x - 1#512

ID2: 0x - 2#512

……….

ID10: 0x - 10#512

Let try.

1 Like
3

@PetruS,

@cuongho’s suggestion is absolutely correct, here is some more information:

image
image567×473 12.8 KB

4

Thank you very much. It is true—using this format:
[slave id]#address
in the object address field works as expected.

In my case, I found the culprit: a cheap “Modbus RTU” relay. When it is connected to the bus line, things start acting strangely and I get “Device not responding” errors, etc.
As soon as it is disconnected, the system becomes stable.

Now I need to find a reliable replacement. Any suggestions based on your experience with similar devices, such as a controlled relay over Modbus RTU/RS485, would be greatly appreciated.

Thank you again for your feedback and support.

5

Hi @PetruS,

As it is difficult for us to verify the long term reliability of 3rd party products, we don’t have any recommendations for Modbus RTU relays suitable for your system. However, perhaps another user can recommend a brand they trust.

6

Hello,

I understand, thank you much for your reply.

Probably some other forum’s member will share her/his experience on a similar matter.

(that’s the great opportunity of such dedicated forum and i am thankful for this.)

Have a good day.

1 Like