Communication Modbus RS485

CODESYS
,
1

Hello everyone,

I am working on a serial RS-485 half-duplex Modbus RTU communication.

I am using a WAGO 750-8112 with CODESYS 3.5.

For the serial interface, I used a MOXA UPort 1150 (USB-to-serial converter for simulation):

  • Pin 3 (R+) of the MOXA connected to pin 1 of the WAGO 750-1652 card
  • Pin 4 (R−) of the MOXA connected to pin 5 of the WAGO 750-1652 card

I am communicating with a Modbus simulator (simulator name).

Unfortunately, I am unable to establish communication with the simulator, whether through I/O check or the API program.

On the 750-1652 card, both LEDs A and E are solid green, while all other LEDs are off.

Do you have any recommendations or suggestions to help me resolve this issue?

API Code:

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2

In your function block call you have I_Port := COM1

COM1 is the built-in DB9 port on the 750-8112. To use the 750-1652 module, replace COM1 with the module’s name in the project tree.

i.e. I_Port := _750_1624_24

3

Thank you for your feedback,

I was able to retrieve data between a simulator installed on a PC and my API via Modbus RS232.

Now, I’m trying to communicate serially between a Schneider TRV00210 module and my API using Modbus RS485 half-duplex. To get started, I’m first communicating with a single device.

Compact NSX Modbus User manual 2009

The LEDs on board A and E are steadily green, B is blinking, and the rest are off. Does this mean I have a problem with my slave device?

For uiReadAddress, should I use hexadecimal or decimal format?

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Regarding the wiring part:

IMG_20260128_164943
IMG_20260128_1649431920×2550 600 KB

4

Hi,

with RS-485 Half Duplex only terminals 1 and 5 are required on 750-1652. Possibly also 3/7 for ground an 4/8 for screen. 2 and 4 are unused. What is connected there?

For LEDs:

E=on, F=off, G=off means RS-485 Half Duplex mode.

B blinking means sending.

C is blinking when receiving.

See manual

100 and 16#64 is the same, sometimes it is easier to use or understand one format or the other.

6

Hello,

Thank you for your response,

You have confirmed my suspicions. I will check with them why they wired terminals 2 and 4.