stm32duino RTC add a subsecond mask to configure the alarm

configure the Alarm with Second mask --> trigs IRQHandler
The Autoclear bit field depends on the RTC ALARM  SSR register.

Signed-off-by: Francois Ramu <francois.ramu@st.com>

Author: FRASTM

src/STM32RTC.cpp

@@ -243,6 +243,7 @@ void STM32RTC::enableAlarm(Alarm_Match match, Alarm name)
     case MATCH_HHMMSS:
     case MATCH_MMSS:
     case MATCH_SS:
+    case MATCH_SUBSEC:
 #ifdef RTC_ALARM_B
       if (name == ALARM_B) {
         RTC_StartAlarm(::ALARM_B, _alarmBDay, _alarmBHours, _alarmBMinutes, _alarmBSeconds,

src/STM32RTC.h

@@ -93,6 +93,7 @@ class STM32RTC {
 
     enum Alarm_Match : uint8_t {
       MATCH_OFF          = OFF_MSK,                          // Never
+      MATCH_SUBSEC       = SUBSEC_MSK,                       // Every Subsecond
       MATCH_SS           = SS_MSK,                           // Every Minute
       MATCH_MMSS         = SS_MSK | MM_MSK,                  // Every Hour
       MATCH_HHMMSS       = SS_MSK | MM_MSK | HH_MSK,         // Every Day

src/rtc.c

@@ -701,11 +701,12 @@ void RTC_StartAlarm(alarm_t name, uint8_t day, uint8_t hours, uint8_t minutes, u
     period = HOUR_AM;
   }
 
+  /* Use alarm A by default because it is common to all STM32 HAL */
+  RTC_AlarmStructure.Alarm = name;
+
   if ((((initFormat == HOUR_FORMAT_24) && IS_RTC_HOUR24(hours)) || IS_RTC_HOUR12(hours))
       && IS_RTC_DATE(day) && IS_RTC_MINUTES(minutes) && IS_RTC_SECONDS(seconds)) {
     /* Set RTC_AlarmStructure with calculated values*/
-    /* Use alarm A by default because it is common to all STM32 HAL */
-    RTC_AlarmStructure.Alarm = name;
     RTC_AlarmStructure.AlarmTime.Seconds = seconds;
     RTC_AlarmStructure.AlarmTime.Minutes = minutes;
     RTC_AlarmStructure.AlarmTime.Hours = hours;
@@ -761,6 +762,38 @@ void RTC_StartAlarm(alarm_t name, uint8_t day, uint8_t hours, uint8_t minutes, u
     UNUSED(mask);
 #endif /* !STM32F1xx */
 
+    /* Set RTC_Alarm */
+    HAL_RTC_SetAlarm_IT(&RtcHandle, &RTC_AlarmStructure, RTC_FORMAT_BIN);
+    HAL_NVIC_SetPriority(RTC_Alarm_IRQn, RTC_IRQ_PRIO, RTC_IRQ_SUBPRIO);
+    HAL_NVIC_EnableIRQ(RTC_Alarm_IRQn);
+  } else {
+    /* We have an SubSecond alarm to set in RTC_BINARY_MIX mode */
+#if defined(RTC_SSR_SS)
+    {
+#if defined(RTC_ALRMASSR_SSCLR)
+      RTC_AlarmStructure.BinaryAutoClr = RTC_ALARMSUBSECONDBIN_AUTOCLR_NO;
+#endif /* RTC_ALRMASSR_SSCLR */
+      RTC_AlarmStructure.AlarmMask = RTC_ALARMMASK_NONE;
+
+#ifdef RTC_ALARM_B
+      if (name == ALARM_B) {
+        /* Expecting RTC_ALARMSUBSECONDBINMASK_NONE for the subsecond mask on ALARM B */
+        RTC_AlarmStructure.AlarmMask = RTC_ALARMMASK_ALL;
+        RTC_AlarmStructure.AlarmSubSecondMask = mask << RTC_ALRMBSSR_MASKSS_Pos;
+      } else
+#endif
+      {
+        /* Expecting RTC_ALARMSUBSECONDBINMASK_NONE for the subsecond mask on ALARM A */
+        RTC_AlarmStructure.AlarmMask = RTC_ALARMMASK_ALL;
+        RTC_AlarmStructure.AlarmSubSecondMask = mask << RTC_ALRMASSR_MASKSS_Pos;
+      }
+      /* Special case for ALARM B configuration for stm32WL Lorawan */
+      RTC_AlarmStructure.AlarmTime.SubSeconds = subSeconds;
+    }
+
+#else
+    UNUSED(subSeconds);
+#endif /* RTC_SSR_SS */
     /* Set RTC_Alarm */
     HAL_RTC_SetAlarm_IT(&RtcHandle, &RTC_AlarmStructure, RTC_FORMAT_BIN);
     HAL_NVIC_SetPriority(RTC_Alarm_IRQn, RTC_IRQ_PRIO, RTC_IRQ_SUBPRIO);

src/rtc.h

@@ -76,7 +76,8 @@ typedef enum {
   /* NOTE: STM32 RTC can't assign a month or a year to an alarm. Those enum
   are kept for compatibility but are ignored inside enableAlarm(). */
   M_MSK   = 16,
-  Y_MSK   = 32
+  Y_MSK   = 32,
+  SUBSEC_MSK = 64
 } alarmMask_t;
 
 typedef enum {