[GitHub] [mynewt-core] sjanc commented on a change in pull request #2413: STM32 RTC based os tick

[GitBox <gi...@apache.org>]

sjanc commented on a change in pull request #2413:
URL: https://github.com/apache/mynewt-core/pull/2413#discussion_r527697145



##########
File path: hw/mcu/stm/stm32_common/src/hal_os_tick.c
##########
@@ -54,6 +55,315 @@ __WFI(void)
 #endif
 #endif
 
+#if MYNEWT_VAL(OS_TICKS_USE_RTC)
+
+#if MYNEWT_VAL(STM32_CLOCK_LSE) && (((32768 / OS_TICKS_PER_SEC) * OS_TICKS_PER_SEC) != 32768)
+#error OS_TICKS_PER_SEC should be divisible by power of 2 like 128, 256, 512, 1024 when OS_TICKS_USE_RTC is enabled.
+#endif
+
+#ifndef HAL_RTC_MODULE_ENABLED
+#error Define HAL_RTC_MODULE_ENABLED in stm32[fl][0-4]xx_hal_conf.h in your bsp
+#endif
+
+#define ASYNCH_PREDIV       7
+#define SYNCH_PREDIV        (32768 / (ASYNCH_PREDIV + 1) - 1)
+#define SUB_SECONDS_BITS    12
+
+#if defined(STM32L0) || defined(STM32F0)
+#define RTC_IRQ RTC_IRQn
+#else
+#define RTC_IRQ RTC_Alarm_IRQn
+#endif
+
+#if defined(STM32L0) || defined(STM32L1)
+#define IS_RTC_ENABLED (RCC->CSR & RCC_CSR_RTCEN)
+#else
+#define IS_RTC_ENABLED (RCC->BDCR & RCC_BDCR_RTCEN)
+#endif
+
+_Static_assert(SUB_SECONDS_BITS == __builtin_popcount(SYNCH_PREDIV), "SUB_SECONDS_BITS should be number of 1s in SYNCH_PREDIV");
+
+/* RTC time of the last tick. */
+static uint32_t last_rtc_time;
+static uint32_t sub_seconds_per_tick;
+static uint8_t sub_seconds_tick_bits;
+
+/* RTC holds UTC time. */
+static RTC_HandleTypeDef rtc = {
+    .Instance = RTC,
+    .Init = {
+        .HourFormat = RTC_HOURFORMAT_24,
+        .OutPut = RTC_OUTPUT_DISABLE,
+        .OutPutPolarity = RTC_OUTPUT_POLARITY_HIGH,
+        .OutPutType = RTC_OUTPUT_TYPE_PUSHPULL,
+    }
+};
+
+/* RTC AlarmA used for OS ticks. */
+static RTC_AlarmTypeDef alarm = {
+    .AlarmTime = {
+        .Hours = 0,
+        .Minutes = 0,
+        .Seconds = 0,
+        .SubSeconds = 0,
+        .TimeFormat = RTC_HOURFORMAT12_AM,
+        .SecondFraction = 0,
+        .DayLightSaving = RTC_DAYLIGHTSAVING_NONE,
+        .StoreOperation = RTC_STOREOPERATION_RESET,
+    },
+    .AlarmMask = RTC_ALARMMASK_ALL,
+    .AlarmSubSecondMask = 0,
+    .Alarm = RTC_ALARM_A,
+};
+
+static uint32_t
+rtc_time_to_sub_seconds(const RTC_TimeTypeDef *time)
+{
+    int32_t sub_seconds;

Review comment:
       is this signed type on purpose?




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