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STM32 LPTICKER : optimize RTC wake up timer init #6370

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Mar 20, 2018
Merged

STM32 LPTICKER : optimize RTC wake up timer init #6370

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37 changes: 22 additions & 15 deletions targets/TARGET_STM/rtc_api.c
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Original file line number Diff line number Diff line change
Expand Up @@ -332,6 +332,11 @@ uint32_t rtc_read_us(void)

void rtc_set_wake_up_timer(uint32_t delta)
{
#define RTC_CLOCK_US (((uint64_t)RTC_CLOCK << 32 ) / 1000000)

uint32_t WakeUpCounter;
uint32_t WakeUpClock;

/* Ex for Wakeup period resolution with RTCCLK=32768 Hz :
* RTCCLK_DIV2: ~122us < wakeup period < ~4s
* RTCCLK_DIV4: ~244us < wakeup period < ~8s
Expand All @@ -340,28 +345,30 @@ void rtc_set_wake_up_timer(uint32_t delta)
* CK_SPRE_16BITS: 1s < wakeup period < (0xFFFF+ 1) x 1 s = 65536 s (18 hours)
* CK_SPRE_17BITS: 18h+1s < wakeup period < (0x1FFFF+ 1) x 1 s = 131072 s (36 hours)
*/
uint32_t WakeUpClock[6] = {RTC_WAKEUPCLOCK_RTCCLK_DIV2, RTC_WAKEUPCLOCK_RTCCLK_DIV4, RTC_WAKEUPCLOCK_RTCCLK_DIV8, RTC_WAKEUPCLOCK_RTCCLK_DIV16, RTC_WAKEUPCLOCK_CK_SPRE_16BITS, RTC_WAKEUPCLOCK_CK_SPRE_17BITS};
uint8_t ClockDiv[4] = {2, 4, 8, 16};
uint32_t WakeUpCounter;
uint8_t DivIndex = 0;

do {
WakeUpCounter = delta / (ClockDiv[DivIndex] * 1000000 / RTC_CLOCK);
DivIndex++;
} while ( (WakeUpCounter > 0xFFFF) && (DivIndex < 4) );

if (WakeUpCounter > 0xFFFF) {
WakeUpCounter = delta / 1000000;
DivIndex++;
if (delta < (0x10000 * 2 / RTC_CLOCK * 1000000) ) { // (0xFFFF + 1) * RTCCLK_DIV2 / RTC_CLOCK * 1s
WakeUpCounter = (((uint64_t)delta * RTC_CLOCK_US) >> 32) >> 1 ;
WakeUpClock = RTC_WAKEUPCLOCK_RTCCLK_DIV2;
} else if (delta < (0x10000 * 4 / RTC_CLOCK * 1000000) ) {
WakeUpCounter = (((uint64_t)delta * RTC_CLOCK_US) >> 32) >> 2 ;
WakeUpClock = RTC_WAKEUPCLOCK_RTCCLK_DIV4;
} else if (delta < (0x10000 * 8 / RTC_CLOCK * 1000000) ) {
WakeUpCounter = (((uint64_t)delta * RTC_CLOCK_US) >> 32) >> 3 ;
WakeUpClock = RTC_WAKEUPCLOCK_RTCCLK_DIV8;
} else if (delta < (0x10000 * 16 / RTC_CLOCK * 1000000) ) {
WakeUpCounter = (((uint64_t)delta * RTC_CLOCK_US) >> 32) >> 4 ;
WakeUpClock = RTC_WAKEUPCLOCK_RTCCLK_DIV16;
} else {
WakeUpCounter = (delta / 1000000) ;
WakeUpClock = RTC_WAKEUPCLOCK_CK_SPRE_16BITS;
}

irq_handler = (void (*)(void))lp_ticker_irq_handler;
NVIC_SetVector(RTC_WKUP_IRQn, (uint32_t)RTC_IRQHandler);
NVIC_EnableIRQ(RTC_WKUP_IRQn);

RtcHandle.Instance = RTC;
if (HAL_RTCEx_SetWakeUpTimer_IT(&RtcHandle, 0xFFFF & WakeUpCounter, WakeUpClock[DivIndex - 1]) != HAL_OK) {
error("rtc_set_wake_up_timer init error (%d)\n", DivIndex);
if (HAL_RTCEx_SetWakeUpTimer_IT(&RtcHandle, (uint32_t)WakeUpCounter, WakeUpClock) != HAL_OK) {
error("rtc_set_wake_up_timer init error\n");
}
}

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