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Modbus Read Registers function Add Swap Words Operation

Joe Tauser

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  • MVP 2023

@Cara Bereck Levy

Take a look at this post, especially near the bottom-


If you look at the post reference chain within thus post you'll see that the question of reading floating point values from energy meters is a very recurring theme.  It's a common occurrence for  word order is always backwards from what Unitronics is expecting.  Ask the Creators how hard it would be to add a new type of Operation to the Registers tabs for function 3 and function 4 - "Read Holding Registers Swap Words".

If you look at the Official Modbus Protocol Specification-


Search for the word "float" you will find no references.  This means the byte order of an IEEE 754 floating point value is not specified anywhere and repeated questions on the forum point to the fact that it's kind of the Wild West out there as to how various manufacturers decide to implement it.  

Unitronics would benefit from making this easier for the end user, as many of them are unaware of this issue.

This dovetails with the release of the new UniClould product as we've seen energy meters are a common addition to a UniStream system and that data will certainly be desired on a UniCloud dashboard.

Just my 2 cents.

Joe T. 

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