How to publish Ewon Flexy tags (Holding Register) through Modbus TCP

Navigate to IO Servers > MODBUS > Modbus TCP Server in the Flexy web interface.
Tick the “Ewon Server” box to enable the Modbus TCP Server.

The Modbus Unit Address is the Slave ID of the Ewon Flexy. In this case, the Slave ID is set to 100.

Go to the tags you wish to publish via the Modbus TCP Server. If you are publishing a tag with Force Read-Only ticked,

the register type of this tag will be input register, which is read only.

If you are publishing a tag without Force Read-Only ticked,

the register type of this tag will be holding register, which supports read and write.

If the wrong Modbus read function is used, you will get a constant 0. Please see screenshot below

You may wonder why it is the input register 231 and the holding register 219 in the screenshot.

It is because the register address in the Flexy starts from 1, and this Modbus client simulator is using 0-based address. Hence, it is shifted by 1.

Some Modbus Master/Client software allows you to select which start address to use.

Also using 3xxxx and 4xxxx to distinguish input registers and holding registers.

If you are publishing a tag as a floating point,

Make sure use 32-bit format is ticked

And it is little-endian for 32-bit word mapping.

Franziska Gültig

Hi Aaron!

Thanks for creating this nice 'How to!'

I'm glad you are part of our community and happy you are are sharing your knowhow with the whole Ewon Community!

I know it takes a lot of work to create something like that! Thank you!

I wish you a happy new year and good luck and success for all your endeavors!

br Franziska Gültig

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