implemented EPM functionality

[nextguyover]

Added functionality for Solis Export Power Manager. Tested to be working for the Solis-EPM1-5G.

[hn]

Thanks for sharing! Frankly, I didn't know that Solis offered such an EPM device until today :)

You have slightly changed the way the RTC update is implemented. Is there a specific reason for this? Both ways are fine, yours is a bit more direct, but more source code bytes.

[nextguyover]

When I ported over your original RTC implementation for the inverter to the EPM, the EPM RTC wasn't being read correctly. From what I remember, it would read a timestamp like 00:00:00 and an incorrect date. This would cause it to set the time each update interval (setting time would work still work).

Changing it to use data[] fixed the issue for me. I don't fully understand your intention with the use of parsed float x as you have done in your original implementation, so I'm not exactly sure what was going wrong...

As per #35 I was unable to get RTC register ranges working on my inverter, so I wasn't able to test your RTC implementation on my inverter either.

[hn]

For a text_sensor variable x is a hex (raw_encode: HEXBYTES) string. With word_from_hex_str you convert back the textual representation to binary.

I have adopted your solution without any changes. Now there are two slightly different approaches for time sync within the project, but since yours is tested, this is a good way to go.