If MICROPY_HW_RTC_USE_BYPASS is enabled the RTC startup goes as follows:
- RTC is started with LSE in bypass mode to begin with
- if that fails to start (after a given timeout) then LSE is reconfigured
in non-bypass
- if that fails to start then RTC is switched to LSI
It can be that LSEON and LSERDY are set yet the RTC is not enabled (this
can happen for example when coming out of the ST DFU mode on an F405 with
the RTC not previously initialised). In such a case the RTC is never
started because the code thinks it's already running. This patch fixes
this case by always checking if RTCEN is set when booting up (and also
testing for a valid RTCSEL value in the case of using an LSE).
With this and previous patches the stm32 port can now be compiled using
object representation D (nan boxing). Note that native code and frozen mpy
files with float constants are currently not supported with this object
representation.
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).
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.
Newer versions of the HAL use names which are cleaner and more
self-consistent amongst the HAL itself. This patch switches to use those
names in most places so it is easier to update the HAL in the future.
Upon boot the RTC early-init function should detect if LSE or LSI is
already selected/running and, if so, use it. When the LSI has previously
(in the previous reset cycle) been selected as the clock source the only
way to reliably tell is if the RTCSEL bits of the RCC_BDCR are set to the
correct LSI value. In particular the RCC_CSR bits for LSI control do not
indicate if the LSI is ready even if it is selected.
This patch removes the check on the RCC_CSR bits for the LSI being on and
ready and only uses the check on the RCC_BDCR to see if the LSI should be
used straightaway. This was tested on a PYBLITEv1.0 and with the patch the
LSI persists correctly as the RTC source as long as the backup domain
remains powered.
Previously, if LSE is selected but fails and the RTC falls back to LSI,
then the rtc_info flags would incorrectly state that LSE is used. This
patch fixes that by setting the bit in rtc_info only after the clock is
ready.
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.
