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STM32 RTC : update and comment prescaler values

pull/5738/head
jeromecoutant 2017-12-04 17:20:56 +01:00 committed by adbridge
parent 3264b21e40
commit 990fb1c18a
1 changed files with 14 additions and 11 deletions
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25
targets/TARGET_STM/rtc_api.c
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@ -36,14 +36,6 @@
static RTC_HandleTypeDef RtcHandle;
#if DEVICE_LOWPOWERTIMER
#define RTC_ASYNCH_PREDIV ((RTC_CLOCK - 1) / 0x8000)
#else
#define RTC_ASYNCH_PREDIV (0x007F)
#endif
#define RTC_SYNCH_PREDIV (RTC_CLOCK / (RTC_ASYNCH_PREDIV + 1) - 1)
#if DEVICE_LOWPOWERTIMER
static void (*irq_handler)(void);
static void RTC_IRQHandler(void);
@ -114,8 +106,19 @@ void rtc_init(void)
RtcHandle.Init.AsynchPrediv = RTC_AUTO_1_SECOND;
#else /* TARGET_STM32F1 */
RtcHandle.Init.HourFormat = RTC_HOURFORMAT_24;
RtcHandle.Init.AsynchPrediv = RTC_ASYNCH_PREDIV;
RtcHandle.Init.SynchPrediv = RTC_SYNCH_PREDIV;
/* PREDIV_A : 7-bit asynchronous prescaler */
#if DEVICE_LOWPOWERTIMER
/* PREDIV_A is set to a small value to improve the SubSeconds resolution */
/* with a 32768Hz clock, PREDIV_A=7 gives a precision of 244us */
RtcHandle.Init.AsynchPrediv = 7;
#else
/* PREDIV_A is set to the maximum value to improve the consumption */
RtcHandle.Init.AsynchPrediv = 0x007F;
#endif
/* PREDIV_S : 15-bit synchronous prescaler */
/* PREDIV_S is set in order to get a 1 Hz clock */
RtcHandle.Init.SynchPrediv = RTC_CLOCK / (RtcHandle.Init.AsynchPrediv + 1) - 1;
RtcHandle.Init.OutPut = RTC_OUTPUT_DISABLE;
RtcHandle.Init.OutPutPolarity = RTC_OUTPUT_POLARITY_HIGH;
RtcHandle.Init.OutPutType = RTC_OUTPUT_TYPE_OPENDRAIN;
@ -304,7 +307,7 @@ static void RTC_IRQHandler(void)
uint32_t rtc_read_subseconds(void)
{
return 1000000.f * ((double)(RTC_SYNCH_PREDIV - RTC->SSR) / (RTC_SYNCH_PREDIV + 1));
return 1000000.f * ((double)((RTC->PRER & RTC_PRER_PREDIV_S) - RTC->SSR) / ((RTC->PRER & RTC_PRER_PREDIV_S) + 1));
}
void rtc_set_wake_up_timer(uint32_t delta)