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samples: boards: stm32 low power blinky for stm32 boards

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Set the prescaler for the stm32_lp_tick_source lptim node.
When the LPTIM is clocked by the LSE with a prescaler
of 16 (lptim freq at 2048Hz) expecting 2048 for the TICKS_PER_SEC.
When the LPTIM is clocked by the LSE with a prescaler
of 32 (lptim freq at 1024Hz) expecting 1024 for the TICKS_PER_SEC.

Signed-off-by: Francois Ramu <francois.ramu@st.com>
This commit is contained in:
Francois Ramu 2023-10-04 17:04:26 +02:00 • committed by Fabio Baltieri
commit bf2b4675d0
4 changed files with 23 additions and 4 deletions
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11
samples/boards/stm32/power_mgmt/blinky/README.rst
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@ -9,6 +9,12 @@ Overview
This sample is a minimum application to demonstrate basic power management
behavior in a basic blinking LED set up using the :ref:`GPIO API <gpio_api>` in
low power context.
Note that lptim instance selected for the low power timer is named **&stm32_lp_tick_source**
When setting a prescaler to decrease the lptimer input clock frequency, the system can sleep
for a longer timeout value and the CONFIG_SYS_CLOCK_TICKS_PER_SEC is adjusted.
For example, when clocking the low power Timer with LSE clock at 32768Hz and adding a
prescaler of <32>, then the kernel sleep period can reach 65536 * 32/32768 = 64 seconds
CONFIG_SYS_CLOCK_TICKS_PER_SEC is set to 1024.
.. _stm32-pm-blinky-sample-requirements:
@ -30,7 +36,10 @@ Build and flash Blinky as follows, changing ``stm32l562e_dk`` for your board:
:goals: build flash
:compact:
After flashing, the LED starts to blink.
After flashing, the LED starts to blink with a fixed period (SLEEP_TIME_MS).
When LPTIM input clock has a prescaler, longer perdiod (up to 64 seconds)
of low power can be tested.
PM configurations
*****************

9
samples/boards/stm32/power_mgmt/blinky/boards/b_u585i_iot02a.overlay Normal file
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@ -0,0 +1,9 @@
/*
* give a prescaler to the lptim clock : LSE / 16 = 2048Hz
* so that the sleep period is of 32s in the sample application
* with a LPTIM1 prescaler of <1> to <8>, CONFIG_SYS_CLOCK_TICKS_PER_SEC is 4096
* with a LPTIM1 prescaler >= <16>, CONFIG_SYS_CLOCK_TICKS_PER_SEC is LSE / prescaler
*/
&stm32_lp_tick_source {
st,prescaler = <16>;
};

6
samples/boards/stm32/power_mgmt/blinky/boards/nucleo_wb55rg.overlay
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@ -1,9 +1,9 @@
/*
* give a prescaler to the lptim clock : LSE / 32 = 1024Hz
* so that the sleep period is of 64s in the sample application
*
* with a LPTIM1 prescaler of <1> to <8>, CONFIG_SYS_CLOCK_TICKS_PER_SEC is 4096
* with a LPTIM1 prescaler >= <16>, CONFIG_SYS_CLOCK_TICKS_PER_SEC is LSE / prescaler
*/
&lptim1 {
&stm32_lp_tick_source {
st,prescaler = <32>;
};

1
samples/boards/stm32/power_mgmt/blinky/prj.conf
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@ -2,3 +2,4 @@ CONFIG_PM=y
CONFIG_PM_DEVICE=y
CONFIG_PM_DEVICE_RUNTIME=y
CONFIG_PM_DEVICE_RUNTIME_EXCLUSIVE=n
CONFIG_ASSERT=y