Edge2Edge: filter undefined integer modbus values

[tcdrop]

This change fixes an issue with the internal OpenEMS Edge-2-Edge communication. It has been discussed in this forum post.

Short Summary: when an OpenEMS edge has an undefined integer channel value, it sets the value to the max. int value (e.g. 65535 for 16bit unsigned integer) in the Modbus API. The master edge then reads this Modbus value, but doesn't recognize it as undefined. Instead, the value gets used just like any other value. This can lead to problems like SOC of 65535%.

This fix adds a converter for integer values to the AbstractEdge2Edge class, that sets channel values to null, if the Modbus value is undefined.

[codecov]

Codecov Report

❌ Patch coverage is 67.44186% with 14 lines in your changes missing coverage. Please review.

Additional details and impacted files

@@              Coverage Diff              @@
##             develop    #3479      +/-   ##
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+ Coverage      59.61%   59.62%   +0.01%     
  Complexity       105      105              
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  Files           3004     3004              
  Lines         130410   130427      +17     
  Branches        9637     9639       +2     
=============================================
+ Hits           77737    77754      +17     
+ Misses         49764    49762       -2     
- Partials        2909     2911       +2     

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[tsicking]

Thanks for the helpful PR. I have some comments, mostly of code style nature.

[tsicking]

I wonder if there is any way to use ModbusRecordUint16.UNDEFINED_VALUE instead of 0xFFFF as I suggested in the forum, but it's not too important.

[tcdrop]

thanks for your feedback! I tried to do that but I couldn't find a nice way of getting the byte array ModbusRecordUint16.UNDEFINED_VALUE to work with this code.
Also I ran into problems with casting between unsigned types Uint16-64 and signed Java types Short, Int, Long. Having it as 0xFFFF worked.

[parapluplu]

Is it feasible to add some kind of unit test for this?

[sfeilmeier]

I used a different approach, reusing the existing UNDEFINED_VALUEs in 41db621.

I added JUnit tests, but did not test it in production yet.

Could anybody test it?