Can I configure STM32L0 to wake up from Standy Mode Every 15 minutes with RTC?
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‎2018-07-30 01:59 PM
I'm using LSI clock, I just have ALRMA for:
1second
1 minute
1 hour.
I woul like to configure it for every 15 second, every 15 minutes.
Thanks
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‎2018-07-31 03:21 AM
You'd need to reconfigure the alarm at each wakeup. For example, to wake up every 15 seconds, you'd have unmasked the seconds (and masked the minutes etc. fields); and then upon each wakeup write to the seconds fields the next time of wakeup, in the 00-15-30-45 sequence.
If you need regular wakeup, maybe it's more efficient to use the wakeup timer (RTC_WUTR).
JW
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‎2018-07-31 03:21 AM
You'd need to reconfigure the alarm at each wakeup. For example, to wake up every 15 seconds, you'd have unmasked the seconds (and masked the minutes etc. fields); and then upon each wakeup write to the seconds fields the next time of wakeup, in the 00-15-30-45 sequence.
If you need regular wakeup, maybe it's more efficient to use the wakeup timer (RTC_WUTR).
JW
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‎2018-11-01 07:13 AM
Sorry about the time to answer.
I used the wakeup timer, and this works fine for my application.
Bruno Sena
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‎2018-11-23 01:16 AM
@Bruno Sena​
How did you configure the wakeup timer?
I am trying it with CUBEMX. -> In the STM32F44_en.DM00135183.pdf under section 22.3.4 "Periodic auto-wakeup"
I found:
The wakeup timer clock input can be:
• RTC clock (RTCCLK) divided by 2, 4, 8, or 16.
When RTCCLK is LSE(32.768 kHz), this allows to configure the wakeup interrupt
period from 122 μs to 32 s, with a resolution down to 61μs.
• ck_spre (usually 1 Hz internal clock)
When ck_spre frequency is 1Hz, this allows to achieve a wakeup time from 1 s to
around 36 hours with one-second resolution. This large programmable time range is
divided in 2 parts:
– from 1s to 18 hours when WUCKSEL [2:1] = 10
– and from around 18h to 36h when WUCKSEL[2:1] = 11. In this last case 216 is
added to the 16-bit counter current value.When the initialization sequence is complete (see Programming the wakeup timer), the timer starts counting
down.When the wakeup function is enabled, the down-counting remains active in
low power modes. In addition, when it reaches 0, the WUTF flag is set in the
RTC_ISR register, and the wakeup counter is automatically reloaded with its
reload value (RTC_WUTR register value).
-> programming the wakeup timer:
The following sequence is required to configure or change the wakeup timer auto-reload
value (WUT[15:0] in RTC_WUTR):
1. Clear WUTE in RTC_CR to disable the wakeup timer.
2. Poll WUTWF until it is set in RTC_ISR to make sure the access to wakeup auto-reload
counter and to WUCKSEL[2:0] bits is allowed. It takes 1 to 2 RTCCLK clock cycles
(due to clock synchronization).
3. Program the wakeup auto-reload value WUT[15:0] and the wakeup clock selection
(WUCKSEL[2:0] bits in RTC_CR).Set WUTE in RTC_CR to enable the timer again.
The wakeup timer restarts down-counting. Due to clock synchronization, the WUTWF
bit is cleared up to 2 RTCCLK clocks cycles after WUTE is cleared.
Lets say for every 15 min?
Beste Regards
Ibrahim Evren
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‎2018-11-23 01:47 AM
(respond before)
• ck_spre (usually 1 Hz internal clock)
When ck_spre frequency is 1Hz, this allows to achieve a wakeup time from 1 s to
around 36 hours with one-second resolution.
I have configured the wakeup Timer with CubeMx:
For 3 Seconds:
In the main.c File I added and using the Wakeup-Callback function: