To use HSI instead of HSE define MICROPY_HW_CLK_USE_HSI as 1 in the board
configuration file. The default is to use HSE.
HSI has been made the default for the NUCLEO_F401RE board to serve as an
example, and because early revisions of this board need a hardware
modification to get HSE working.
This ensures that on first boot the most optimal settings are used for the
voltage scaling and flash latency (for F7 MCUs).
This commit also provides more fine-grained control for the flash latency
settings.
MCUs that have a PLLSAI can use it to generate a 48MHz clock for USB, SDIO
and RNG peripherals. In such cases the SYSCLK is not restricted to values
that allow the system PLL to generate 48MHz, but can be any frequency.
This patch allows such configurability for F7 MCUs, allowing the SYSCLK to
be set in 2MHz increments via machine.freq(). PLLSAI will only be enabled
if needed, and consumes about 1mA extra. This fine grained control of
frequency is useful to get accurate SPI baudrates, for example.
For a given IRQn (eg UART) there's no need to carry around both a PRI and
SUBPRI value (eg IRQ_PRI_UART, IRQ_SUBPRI_UART). Instead, the IRQ_PRI_UART
value has been changed in this patch to be the encoded hardware value,
using NVIC_EncodePriority. This way the NVIC_SetPriority function can be
used directly, instead of going through HAL_NVIC_SetPriority which must do
extra processing to encode the PRI+SUBPRI.
For a priority grouping of 4 (4 bits for preempt priority, 0 bits for the
sub-priority), which is used in the stm32 port, the IRQ_PRI_xxx constants
remain unchanged in their value.
This patch also "fixes" the use of raise_irq_pri() which should be passed
the encoded value (but as mentioned above the unencoded value is the same
as the encoded value for priority grouping 4, so there was no bug from this
error).
After calling HAL_SYSTICK_Config the SysTick IRQ priority is set to 15, the
lowest priority. This commit reconfigures the IRQ priority to the desired
TICK_INT_PRIORITY value.
To use HSE bypass mode the board should define:
#define MICROPY_HW_CLK_USE_BYPASS (1)
If this is not defined, or is defined to 0, then HSE oscillator mode is
used.
The CMSIS files for the STM32 range provide macros to distinguish between
the different MCU series: STM32F4, STM32F7, STM32H7, STM32L4, etc. Prefer
to use these instead of custom ones.
This is to keep the top-level directory clean, to make it clear what is
core and what is a port, and to allow the repository to grow with new ports
in a sustainable way.
