How to read Real Value on Modbus for codesys v3.5

CODESYS
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1

Hello!
I have a device that I communicate with modbus tcp. The data it sent me is of real type. How should I read this data in codesys by converting?
Data is read word by word in codesys 3.5

2
  1. Create a DUT og type UNION with a Word array of size 2 and a REAL value.
  2. Copy the two modbus words (per real value) into the unions array.
  3. Read the REAL value out of the UNION directly.
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4

Why you use pointer ?

5

Another approach that uses overlapped memory, using the compiler to convert between WORD and REAL. Tip: make sure that the REAL is on an even byte boundary in the server.

VAR
   myWORD_LowByte AT %MW0 : WORD;
   myWORD_HighByte AT %MW1 : WORD; 
   myREAL AT %MW0 : REAL;
END_VAR
 
myWORD_LowByte := ModbusArray[0];
myWORD_HIghByte := ModbusArray[1];
myReal; // This will be the REAL Value
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6

I want to ask one more thing. What should I do when the incoming data is big endian or little endian?

7

You can map it to the byte level with the same approach, and change the mapping as needed.

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Pl. check the different methods

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