Good afternoon, I am asking for help and advice from experts.

The task is following

To connect the frequency converter (FC) using the protocol Modbus RTU to Siemens Logo. The frequency converter is not Siemens.

For connection BM and FC the special RS485 to Ethernet converter (WAVESHARE) will be used. (Inside this converter device number, data port (502), IP address and baud rate (9600) were configured).

An unmanaged switch (TP-LINK LS1005G) was used to organize the local network.

IP address BM 192.168.11.102

IP address converter (and modbus device) 192.168.11.102.

Such connection scheme has been successfully tested for reading data from a temperature and humidity sensor using the Modbus protocol (Temperature and humidity transmitter SHT20).

Unfortunately, I was only able to read data from the modbass device. In this case, the following setting of the network analog input was used. I cannot write data to Modbus device. Although such a possibility exists. I could not get.
Please look attachment "Network analog input configuration"

In connection with the above, I have a question and request.

How can I request and answer dates to Modbus device?

For example:

The frequency converter supports the following function codes:

- 0 x 03 reading several registers, request and answer

- 0 x 06 single register entry, request and answer

How can I make such procedure?

What functions and constants can I use to solve this problem?

Must I use “Configuring Modbus client connections”?

And how must I configure”Data transfer” if I will need it.

Now real number and codes.

I must put the rotation speed (for example 32 Hz) Decimal number 320 Hexadecimal 140.

Devise address (it is easy. Unit ID)

Function code (for example 0x06)

Register address (for example 0x2001. In my frequency converter this address is responsible for setting the rotation speed). Two bytes. The first 0x20 the second 0x01.

Is it Modbus address?

Register value (the rotation speed)  (must be two bytes) 0x01   and 0x40. How can I do it?

CRC  What is it? How does’ it used?

Next part

How can I receive answer from Modbus device? I need take rotation speed and put it into Message text.

Thank You

Closed cause question posted twice.

The second thread with the subject connecting a Modbass device to LOGO! is published within the conference LOGO! - Communication.