This PR add some enhancement and flexibility.

• variant.h is now independent and does not rely on any header.

• Default STM32 HAL configuration:

  • Before each variants had to include the STM32 HAL configuration file: stm32yyxx_hal_conf.h with yy the STM32 series: f0, f1, f2, f3, f4, g0, f7, h7, l0, l1, l4, wb
    Those files were almost the same for the all series.
    With a default one per series this avoid to add it to the variant folder.
  • Extra HAL module can be enabled in variant.h if required or in a file named (at sketch level): hal_conf_extra.h
  • Custom HAL configuration file can replace the default one by adding a file named (at sketch level):
    hal_conf_custom.h .
  • Some dedicated definitions can be redefined:
    • TICK_INT_PRIORITY
    • PREFETCH_ENABLE
    • INSTRUCTION_CACHE_ENABLE
    • DATA_CACHE_ENABLE
    • USE_SPI_CRC

• Some HAL modules can now be disabled if user does not use the feature by defining one or more following values (solve Disable HAL feature when not used in the sketch #228):

  • HAL_ADC_MODULE_DISABLED
  • HAL_I2C_MODULE_DISABLED
  • HAL_RTC_MODULE_DISABLED
  • HAL_SPI_MODULE_DISABLED
  • HAL_DAC_MODULE_DISABLED
  • HAL_ETH_MODULE_DISABLED
  • HAL_SD_MODULE_DISABLED
  • HAL_QSPI_MODULE_DISABLED
  • HAL_EXTI_MODULE_DISABLED
  • HAL_TIM_MODULE_DISABLED

Note: HAL_UART_MODULE_ENABLED and HAL_PCD_MODULE_ENABLED are handled thanks Arduino menu.

For example, default Blink sketch for Nucleo L031K6:

• With default option (Serial is enabled):

Sketch uses 11208 bytes (34%) of program storage space. Maximum is 32768 bytes.
Global variables use 780 bytes (9%) of dynamic memory, leaving 7412 bytes for local variables. Maximum is 8192 bytes.

• With all HAL_*_MODULE_DISABLED defined in hal_conf_extra.h and Serial disabled:

Sketch uses 4340 bytes (13%) of program storage space. Maximum is 32768 bytes.
Global variables use 52 bytes (0%) of dynamic memory, leaving 8140 bytes for local variables. Maximum is 8192 bytes.

Refer to HAL configuration WiKi page