Support sleeping fractions of seconds

Author: angelnu

README.md

@@ -3,23 +3,24 @@ Arduino library to support STM32 Low Power.
 
 ## Requirement
  * [Arduino_Core_STM32](https://github.com/stm32duino/Arduino_Core_STM32) version >= 1.3.0
- * [STM32RTC](https://github.com/stm32duino/STM32RTC)
 
 ## API
 
 * **`void begin()`**: configure the Low Power
 
 * **`void idle(uint32_t millis)`**: enter in idle mode  
-**param** millis (optional): number of milliseconds before to exit the mode. At least 1000 ms. The RTC is used in alarm mode to wakeup the chip in millis milliseconds.
+**param** millis (optional): number of milliseconds before to exit the mode. The RTC is used in alarm mode to wakeup the chip in millis milliseconds.
 
 * **`void sleep(uint32_t millis)`**: enter in sleep mode  
-**param** millis (optional): number of milliseconds before to exit the mode. At least 1000 ms. The RTC is used in alarm mode to wakeup the chip in millis milliseconds.
+**param** millis (optional): number of milliseconds before to exit the mode. he RTC is used in alarm mode to wakeup the chip in millis milliseconds.
 
 * **`void deepSleep(uint32_t millis)`**: enter in deepSleep mode  
-**param** millis (optional): number of milliseconds before to exit the mode. At least 1000 ms. The RTC is used in alarm mode to wakeup the chip in millis milliseconds.
+**param** millis (optional): number of milliseconds before to exit the mode. The RTC is used in alarm mode to wakeup the chip in millis milliseconds.
 
 * **`void shutdown(uint32_t millis)`**: enter in shutdown mode
-**param** millis (optional): number of milliseconds before to exit the mode. At least 1000 ms. The RTC is used in alarm mode to wakeup the board in millis milliseconds.
+**param** millis (optional): number of milliseconds before to exit the mode. The RTC is used in alarm mode to wakeup the board in millis milliseconds.
+
+**Note: With [STM32RTC](https://github.com/stm32duino/STM32RTC) version lower than 1.1.0, the minimum number of milliseconds is 1000 ms.**
 
 * **`void attachInterruptWakeup(uint32_t pin, voidFuncPtrVoid callback, uint32_t mode)`**: Enable GPIO pin in interrupt mode. If the pin is a wakeup pin, it is configured as wakeup source (see board documentation).  
 **param** pin: pin number  

library.properties

@@ -1,5 +1,5 @@
 name=STM32duino Low Power
-version=1.0.3
+version=1.1.0
 author=Wi6Labs
 maintainer=stm32duino
 sentence=Power save primitives features for STM32 boards

src/STM32LowPower.cpp

@@ -167,7 +167,7 @@ void STM32LowPower::enableWakeupFrom(STM32RTC *rtc, voidFuncPtr callback, void *
 
 /**
   * @brief  Configure the RTC alarm
-  * @param  millis: time of the alarm in milliseconds. At least 1000ms.
+  * @param  millis: time of the alarm in milliseconds.
   * @param  lp_mode: low power mode targeted.
   * @retval None
   */
@@ -202,12 +202,28 @@ void STM32LowPower::programRtcWakeUp(uint32_t millis, LP_Mode lp_mode)
   if (millis > 0) {
     // Convert millisecond to second
     sec = millis / 1000;
+
+#if defined(STM32_RTC_VERSION) && (STM32_RTC_VERSION  >= 0x01010000)
+    uint32_t epoc_ms;
+    millis = millis % 1000;
+    epoc = rtc.getEpoch(&epoc_ms);
+
+    //Update epoch_ms - might need to add a second to epoch
+    epoc_ms += millis;
+    if (epoc_ms >= 1000) {
+      sec ++;
+      epoc_ms -= 1000;
+    }
+
+    rtc.setAlarmEpoch(epoc + sec, STM32RTC::MATCH_DHHMMSS, epoc_ms);
+#else
     // Minimum is 1 second
     if (sec == 0) {
       sec = 1;
     }
-
     epoc = rtc.getEpoch();
+
     rtc.setAlarmEpoch(epoc + sec);
+#endif
   }
 }