This provides an alternative esp32-specific SPI driver with ops that can be
swapped in place of the gpio bitbang one.
The pinmux info and lws gpio driver and other data in the spi bitbang
struct are used as-is by the DMA one.
New ops are provided which are able to allocate and free DMA-able memory so
the device drivers can prepare directly usable buffers. Bounce through to
DMA-able buffers is also transparently supported.
Add lws_display and minimal example support for esp32-wrover to match wsp32-heltec-wb32
Since no usable buttons that don't affect something else on wrover kit, assumes
a button to 0V on GPIO14.
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.
