chore: set clock source and (a)synchronous prescalers together

(a)synchronous prescalers values depend on the RTC clock source.

Signed-off-by: Frederic Pillon <frederic.pillon@st.com>

Author: fpistm

README.md

@@ -31,7 +31,7 @@ _RTC hours mode (12 or 24)_
 
 _RTC clock source_
 * **`Source_Clock getClockSource(void)`** : get current clock source.
-* **`void setClockSource(Source_Clock source)`** : this function must be called before `begin()`.
+* **`void setClockSource(Source_Clock source, uint32_t predivA, uint32_t predivS)`** : set the clock source (`LSI_CLOCK`, `LSE_CLOCK` or `HSE_CLOCK`) and (a)synchronous prescaler values. This function must be called before `begin()`. Use `(PREDIVA_MAX + 1)` and `(PREDIVS_MAX +1)` to reset value and use computed ones. Those values have to match the following conditions: **_1Hz = RTC CLK source / ((predivA + 1) * (predivS + 1))_**
 
 _RTC Asynchronous and Synchronous prescaler_
 * **`void getPrediv(uint32_t *predivA, uint32_t *predivS)`** : get (a)synchronous prescaler values if set else computed ones for the current clock source.

src/STM32RTC.cpp

@@ -117,18 +117,23 @@ STM32RTC::Source_Clock STM32RTC::getClockSource(void)
 }
 
 /**
-  * @brief set the RTC clock source. By default LSI clock is selected. This
-  * method must be called before begin().
+  * @brief set the RTC clock source and user (a)synchronous prescalers values.
+  * @note  By default LSI clock is selected. This method must be called before begin().
   * @param source: clock source: LSI_CLOCK, LSE_CLOCK or HSE_CLOCK
+  * @param  predivA: Asynchronous prescaler value.
+  * @note   Reset value: RTC_AUTO_1_SECOND for STM32F1xx series, else (PREDIVA_MAX + 1)
+  * @param  predivS: Synchronous prescaler value.
+  * @note   Reset value: (PREDIVS_MAX + 1), not used for STM32F1xx series.
   * @retval None
   */
-void STM32RTC::setClockSource(Source_Clock source)
+void STM32RTC::setClockSource(Source_Clock source, uint32_t predivA, uint32_t predivS)
 {
   if (IS_CLOCK_SOURCE(source)) {
     _clockSource = source;
     RTC_SetClockSource((_clockSource == LSE_CLOCK) ? ::LSE_CLOCK :
                        (_clockSource == HSE_CLOCK) ? ::HSE_CLOCK : ::LSI_CLOCK);
   }
+  RTC_setPrediv(predivA, predivS);
 }
 
 /**
@@ -151,7 +156,7 @@ void STM32RTC::getPrediv(uint32_t *predivA, uint32_t *predivS)
 }
 
 /**
-  * @brief  set user (a)synchronous prescalers value.
+  * @brief  set user (a)synchronous prescalers values.
   * @note   This method must be called before begin().
   * @param  predivA: Asynchronous prescaler value.
   * @note   Reset value: RTC_AUTO_1_SECOND for STM32F1xx series, else (PREDIVA_MAX + 1)
@@ -161,7 +166,7 @@ void STM32RTC::getPrediv(uint32_t *predivA, uint32_t *predivS)
   */
 void STM32RTC::setPrediv(uint32_t predivA, uint32_t predivS)
 {
-  RTC_setPrediv(predivA, predivS);
+  setClockSource(_clockSource, predivA, predivS);
 }
 
 /**

src/STM32RTC.h

@@ -126,7 +126,9 @@ class STM32RTC {
     void end(void);
 
     Source_Clock getClockSource(void);
-    void setClockSource(Source_Clock source);
+    void setClockSource(Source_Clock source, uint32_t predivA = (PREDIVA_MAX + 1), uint32_t predivS = (PREDIVS_MAX + 1));
+    void getPrediv(uint32_t *predivA, uint32_t *predivS);
+    void setPrediv(uint32_t predivA, uint32_t predivS);
 
     void enableAlarm(Alarm_Match match, Alarm name = ALARM_A);
     void disableAlarm(Alarm name = ALARM_A);
@@ -212,9 +214,6 @@ class STM32RTC {
     void setAlarmEpoch(time_t ts, Alarm_Match match, Alarm name);
     void setAlarmEpoch(time_t ts, Alarm_Match match = MATCH_DHHMMSS, uint32_t subSeconds = 0, Alarm name = ALARM_A);
 
-    void getPrediv(uint32_t *predivA, uint32_t *predivS);
-    void setPrediv(uint32_t predivA, uint32_t predivS);
-
     bool isConfigured(void)
     {
       return RTC_IsConfigured();