Update example to add clock source selection

Fix #8

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

Author: fpistm

examples/Epoch/Epoch.ino

@@ -44,6 +44,10 @@ STM32RTC& rtc = STM32RTC::getInstance();
 void setup() {
   Serial.begin(9600);
 
+  // Select RTC clock source: RTC_LSI_CLOCK, RTC_LSE_CLOCK or RTC_HSE_CLOCK.
+  // By default the LSI is selected as source.
+  //rtc.setClockSource(STM32RTC::RTC_LSE_CLOCK);
+
   rtc.begin(); // initialize RTC 24H format
 
   rtc.setEpoch(1451606400); // Jan 1, 2016

examples/SimpleRTC/SimpleRTC.ino

@@ -57,6 +57,10 @@ void setup()
 {
   Serial.begin(9600);
 
+  // Select RTC clock source: RTC_LSI_CLOCK, RTC_LSE_CLOCK or RTC_HSE_CLOCK.
+  // By default the LSI is selected as source.
+  //rtc.setClockSource(STM32RTC::RTC_LSE_CLOCK);
+
   rtc.begin(); // initialize RTC 24H format
 
   // Set the time

examples/advancedRTCAlarm/advancedRTCAlarm.ino

@@ -40,6 +40,10 @@ void setup()
 {
   Serial.begin(9600);
 
+  // Select RTC clock source: RTC_LSI_CLOCK, RTC_LSE_CLOCK or RTC_HSE_CLOCK.
+  // By default the LSI is selected as source.
+  //rtc.setClockSource(STM32RTC::RTC_LSE_CLOCK);
+
   rtc.begin(); // initialize RTC 24H format
 
   rtc.setTime(hours, minutes, seconds);

examples/simpleRTCAlarm/simpleRTCAlarm.ino

@@ -55,6 +55,10 @@ void setup()
 {
   Serial.begin(9600);
 
+  // Select RTC clock source: RTC_LSI_CLOCK, RTC_LSE_CLOCK or RTC_HSE_CLOCK.
+  // By default the LSI is selected as source.
+  //rtc.setClockSource(STM32RTC::RTC_LSE_CLOCK);
+
   rtc.begin(); // initialize RTC 24H format
 
   rtc.setTime(hours, minutes, seconds);