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STM32 LPTICKER with RTC : better sleep time #8777

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Merged
merged 2 commits into from
Dec 20, 2018
Merged

STM32 LPTICKER with RTC : better sleep time #8777

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9da5e48
STM32 RTC : skip rtc_write if possible
jeromecoutant Nov 16, 2018
25e6917
STM32 LPTICKER with RTC : optimise sleep duration
jeromecoutant Nov 16, 2018
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50 changes: 45 additions & 5 deletions targets/TARGET_STM/rtc_api.c
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Original file line number Diff line number Diff line change
Expand Up @@ -207,6 +207,11 @@ void rtc_write(time_t t)
RTC_DateTypeDef dateStruct = {0};
RTC_TimeTypeDef timeStruct = {0};

/* if the requested time is the current time, no need to continue */
if (t == rtc_read()) {
return;
}

core_util_critical_section_enter();
RtcHandle.Instance = RTC;

Expand Down Expand Up @@ -341,25 +346,60 @@ uint32_t rtc_read_lp(void)

void rtc_set_wake_up_timer(timestamp_t timestamp)
{
/* RTC periodic auto wake up timer is used
* This WakeUpTimer is loaded to an init value => WakeUpCounter
* then timer starts counting down (even in low-power modes)
* When it reaches 0, the WUTF flag is set in the RTC_ISR register
*/
uint32_t WakeUpCounter;
uint32_t current_lp_time;
uint32_t WakeUpClock = RTC_WAKEUPCLOCK_RTCCLK_DIV4;

current_lp_time = rtc_read_lp();
core_util_critical_section_enter();

/* MBED API gives the timestamp value to set
* WakeUpCounter is then the delta between timestamp and the current tick (LPTICKER_counter)
* If the current tick preceeds timestamp value, max U32 is added
*/
uint32_t current_lp_time = rtc_read_lp();
if (timestamp < current_lp_time) {
WakeUpCounter = 0xFFFFFFFF - current_lp_time + timestamp;
} else {
WakeUpCounter = timestamp - current_lp_time;
}

/* RTC WakeUpCounter is 16 bits
* Corresponding time value depends on WakeUpClock
* - RTC clock divided by 4 : max WakeUpCounter value is 8s (precision around 122 us)
* - RTC clock divided by 8 : max WakeUpCounter value is 16s (precision around 244 us)
* - RTC clock divided by 16 : max WakeUpCounter value is 32s (precision around 488 us)
* - 1 Hz internal clock 16b : max WakeUpCounter value is 18h (precision 1 s)
* - 1 Hz internal clock 17b : max WakeUpCounter value is 36h (precision 1 s)
*/
if (WakeUpCounter > 0xFFFF) {
WakeUpCounter = 0xFFFF;
WakeUpClock = RTC_WAKEUPCLOCK_RTCCLK_DIV8;
WakeUpCounter = WakeUpCounter / 2;

if (WakeUpCounter > 0xFFFF) {
WakeUpClock = RTC_WAKEUPCLOCK_RTCCLK_DIV16;
WakeUpCounter = WakeUpCounter / 2;

if (WakeUpCounter > 0xFFFF) {
/* Tick value needs to be translated in seconds : TICK * 16 (previous div16 value) / RTC clock (32768) */
WakeUpClock = RTC_WAKEUPCLOCK_CK_SPRE_16BITS;
WakeUpCounter = WakeUpCounter / 2048;

if (WakeUpCounter > 0xFFFF) {
/* In this case 2^16 is added to the 16-bit counter value */
WakeUpClock = RTC_WAKEUPCLOCK_CK_SPRE_17BITS;
WakeUpCounter = WakeUpCounter - 0x10000;
}
}
}
}

core_util_critical_section_enter();
RtcHandle.Instance = RTC;
HAL_RTCEx_DeactivateWakeUpTimer(&RtcHandle);
if (HAL_RTCEx_SetWakeUpTimer_IT(&RtcHandle, WakeUpCounter, RTC_WAKEUPCLOCK_RTCCLK_DIV4) != HAL_OK) {
if (HAL_RTCEx_SetWakeUpTimer_IT(&RtcHandle, WakeUpCounter, WakeUpClock) != HAL_OK) {
error("rtc_set_wake_up_timer init error\n");
}

Expand Down