STM32L1, STM32L4 RTC: add periodic interrupts, update L1 RTC implementation
* STM32L4 RTC: add support experimental CONFIG_RTC_PERIODIC
* STM32 RTC: separate STM32L1 RTC into a separate file
STM32L1 RTC is very close to F4 or L4 versions, with two alarms
and periodic wakeup support so backported L4 peripheral to L1.
* RTC: add periodic alarms to upper and lower halves
Approved-by: Gregory Nutt <gnutt@nuttx.org>
- compile issues because of missing RTC_MAGIC #defines
- missing functionality based on RTC_MAGIC in RTC based on stm32_rtcounter.c
- IRQ setup from up_rtc_initialize was later reset in up_irqinitialize
- write access to backup registers without enabling access to backup domain
- possible races in set/cancel alarm
tested with STM32F103C8 only
device now wakes up from forced STANDBY mode by alarm
New interface allows checking if RTC time has been set. This allows to application to detect if RTC has valid time (after
reset) or should application attempt to get real time by other means (for example, by launching ntpclient or GPS).
In stm32_rtcc.c the up_rtcinitialize() logic doesn't work with the LSI. The check on RTC_MAGIC on the BK0R register lead to rtc_setup() call that rightfully enables the lsi clock; but the next times, when the rtc is already setup, the rtc_resume() call does NOT start the lsi clock!
The right place to put LSE/LSI initialisation is inside stm32_stdclockconfig() in stm32fxxxxx_rcc.c. Doing this I checked the possible uses of the LSI and the LSE sources: the LSI can be used for RTC and/or the IWDG, while the LSE only for the RTC (and to output the MCO1 pin)..
This change is not verifed for any other platforms.
From Leo Aloe3132
Add a skeleton implementation of the RTC lower half interface at arch/arm/src/stm32/stm32_rtc_lowerhalf.c. This is just the framework for the RTC lower half. None of the interface methods have yet been implemetned.
