UART devices are now configured using static array in header files instead of static variables in implementation to be able to define UART_NUMOF using the size of the array instead of a variable.
DAC pins are now configured using static arrays in header files instead of static variables in implementation to be able to define DAC_NUMOF using the size of these arrays instead of a variable.
ADC pins are now configured using static arrays in header files instead of static variables in implementation to be able to define ADC_NUMOF using the size of these arrays instead of a variable.
Functions that are used by ADC and DAC peripherals are moved to a new submodule periph_adc_ctrl. This is necessary to compile separate submodules for ADC and DAC.
The GPIO for RX has to be initialized as input before the GPIO for TX can be initialized as output. Otherwise it could lead to creash if RX GPIO was used as output before.
Function uart_set_baudrate which is only used internally was made static and renamed to _uart_set_baudrate to indicate that it is an internal function. Furthermore, an additional waiting for flushed TX FIFO added. The reconfiguration is now handled as critical section.
An additional _ for static symbols has been added by mistake and should be removed. This will make future merging with the reimplementation of ESP8266 easier.
Although ESP32 has four SPI controllers, only two of them can be effectively used (HSP and VSPI). The third one (FSPI) is used for external memory such as flash and PSRAM and can not be used for peripherals. FSPI is therefore removed from the API. In addition, the SPI0_DEV and SPI1_DEV configuration parameters are renamed SPI0_CTRL and SPI1_CTRL to better describe what they define and to avoid confusion with SPI_DEV (0) and SPI_DEV (1).
Xtensa newlib version requires pthread_setcancelstate as symbol. Therefore, the module pthread was always used, which in turn requires the module xtimer. The xtimer module, however, uses TIMER_DEV(0). Therefore, tests/timers failed for TIMER_DEV(0).
