Make a start on generic peripheral and bus drivers to provide
meta-functionality regardless of platform.
On the one hand this simply provides...
- bitbang i2c on top of esp-idf gpio apis
- ssd1306 oled chip driver as found on Heltec WB32
- modifications to the minimal example test for esp32 to use that
... on the other hand, those capabilities are provided by creating:
- an abstract i2c class object
- an abstract gpio class object
- i2c class implementation using the abstract gpio for bitbang
- an abstract display class object
- an abstract display state (brightness, animated change,
on/off/init tracking, autodim after inactive, auto-off /
blanking after inactive)
... with the intention, eg, you only have to add a platform
implementation for the gpio to be able to use the i2c-based
display drivers and state handling, and i2c bitbang, without
any other modifications.
LWS_EXTERN needs to be empty for windows when declaring functions in the
headers. But for data, it needs the explicit extern otherwise on windows
or mingw based builds, it thinks we are redeclaring the data each time.
Establish a new distributed CMake architecture with CMake code related to
a source directory moving to be in the subdir in its own CMakeLists.txt.
In particular, there's now one in ./lib which calls through to ones
further down the directory tree like ./lib/plat/xxx, ./lib/roles/xxx etc.
This cuts the main CMakelists.txt from 98KB -> 33KB, about a 66% reduction,
and it's much easier to maintain sub-CMakeLists.txt that are in the same
directory as the sources they manage, and conceal all the details that that
level.
Child CMakelists.txt become responsible for:
- include_directories() definition (this is not supported by CMake
directly, it passes it back up via PARENT_SCOPE vars in helper
macros)
- Addition child CMakeLists.txt inclusion, for example toplevel ->
role -> role subdir
- Source file addition to the build
- Dependent library path resolution... this is now a private thing
in the child CMakeLists.txt, it just passes back any adaptations
to include_directories() and the LIB_LIST without filling the
parent namespace with the details
