* show charge controller temperature in live view
* send hex requests right after decoding a frame. this seems to have the
best chance of getting an answer to all requests.
* deem 0xFFFFFFFF value of network total DC power as invalid indicator.
neither network state, nor network info, nor network mode seem to
indicate that the charge controller is part of a VE.Smart network. for
that reason, we revert to always querying the network total DC power
value, but testing it for max(uin32_t) value, which seems to indicate
that the charge controller is not part of a VE.Smart network.
* improve (verbose) logging, e.g., use _logId, and print names of
response codes and known registers, always print error messages,
add additional tests to prevent overly verbose messages.
* move hex protocol definitions to VeDirectData.h header
and use enum classes
* define register addresses in enum class
* move values retrieved through hex protocol into main MPPT data struct
* do not send HEX requests if the serial interface cannot send data
* detect whether smart battery sense temperature is available
* web app: make all VE.Direct sub-cards iterable. this makes addind more
values much simpler and saves a bunch of code in the web app.
* make VeDirectFrameHandler state a type-safe enum class
* unindent MPPT controller loop()
* whitespace cleanup
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