* introduce VictronMpptClass
this solves a design issue where the loop() method of a static instance
of VeDirectMpptController, which is part of library code, is called as
part of the main loop() implementation. that is a problem because the
call to this loop() must be handled differently from all other calls:
the lib does not know whether or not the feature is enabled at all.
also, the instance would not be initialized when enabling the feature
during normal operation. that would even lead to a nullptr exception
since the pointer to the serial implementation is still uninitialized.
this new intermediate class is implemented with the support for multiple
Victron charge controllers in mind. adding support for more charge
controllers should be more viable than ever.
fixes#481.
related to #397#129.
* VE.Direct: move get.*AsString methods to respective structs
those structs, which hold the data to be translated into strings, know
best how to translate them. this change also simplifies access to those
translation, as no parameter must be handed to the respective methods:
they now act upon the data of the instance they are called for. adds
constness to those methods.
* VE.Direct: simplify and clean up get.*AsString methods
use a map, which is much easier to maintain and which reads much easier.
move the strings to flash memory to save RAM.
* DPL: use VictronMpptClass::getPowerOutputWatts method
remove redundant calculation of output power from DPL. consider
separation of concern: VictronMpptClass will provide the total solar
output power. the DPL shall not concern itself about how that value is
calculated and it certainly should be unaware about how many MPPT charge
controllers there actually are.
* VE.Direct: avoid shadowing struct member "P"
P was part of the base struct for both MPPT and SmartShunt controller.
however, P was also part of the SmartShunt controller data struct,
shadowing the member in the base struct.
since P has slightly different meaning in MPPT versus SmartShunt, and
since P is calculated for MPPT controllers but read from SmartShunts, P
now lives in both derived structs, but not in the base struct.
* VE.Direct: isDataValid(): avoid copying data structs
pass a const reference to the base class implementation of isDataValid()
rather than a copy of the whole struct.
* VE.Direct: unify logging of text events
* VE.Direct: stop processing text event if handled by base
in case the base class processed a text event, do not try to match it
against values that are only valid in the derived class -- none will
match.
* VE.Direct MPPT: manage data in a shared_ptr
instead of handing out a reference to a struct which is part of a class
instance that may disappear, e.g., on a config change, we now manage the
lifetime of said data structure using a shared_ptr and hand out copies
of that shared_ptr. this makes sure that users have a valid copy of the
data as long as they hold the shared_ptr.
* VE.Direct MPPT: implement getDataAgeMillis()
this works even if millis() wraps around.
* VE.Direct: process frame end event only for valid frames
save a parameters, save a level of indention, save a function call for
invalid frames.
