1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
|
/**
@page LPTIM_Timeout LPTIM Timeout example with LSE clock source
@verbatim
******************************************************************************
* @file LPTIM/LPTIM_Timeout/readme.txt
* @author MCD Application Team
* @brief Description of the LPTIM Timeout example.
******************************************************************************
*
* Copyright (c) 2019-2021 STMicroelectronics.
* All rights reserved.
*
* This software is licensed under terms that can be found in the LICENSE file
* in the root directory of this software component.
* If no LICENSE file comes with this software, it is provided AS-IS.
*
******************************************************************************
@endverbatim
@par Example Description
How to implement, through the HAL LPTIM API, a timeout with the LPTIMER peripheral, to wake up
the system from a low-power mode.
The main() function configures the LPTIMER and goes in STOP mode.
In order to start the timer a first trigger is needed on (PC3)(LPTIM_ETR).
Any successive trigger event on (PC3) will reset the counter and the timer
will restart. The timeout value corresponds to the compare value (32768).
If after the first trigger no other trigger occurs within the expected time frame,
the MCU is woken-up by the compare match event and LED2 toggles.
In this example the LPTIM is clocked by the LSE
Timeout = (Compare + 1) / LPTIM_Clock
= (32767 + 1) / LSE_Clock_Frequency
Once the system is woken up it remains in run mode. The led keeps toggling each time the timer expires.
@note This example can not be used in DEBUG mode, this is due to the fact
that the Cortex-M4 core is no longer clocked during low power mode
so debugging features are disabled.
@note Care must be taken when using HAL_Delay(), this function provides accurate
delay (in milliseconds) based on variable incremented in SysTick ISR. This
implies that if HAL_Delay() is called from a peripheral ISR process, then
the SysTick interrupt must have higher priority (numerically lower)
than the peripheral interrupt. Otherwise the caller ISR process will be blocked.
To change the SysTick interrupt priority you have to use HAL_NVIC_SetPriority() function.
@note This example needs to ensure that the SysTick time base is always set to 1 millisecond
to have correct HAL operation.
@par Keywords
Timer, Low Power Timer, Wake up, Stop mode, LSI, Run mode
@par Directory contents
- LPTIM/LPTIM_Timeout/Inc/stm32wbxx_hal_conf.h HAL configuration file
- LPTIM/LPTIM_Timeout/Inc/stm32wbxx_it.h Interrupt handlers header file
- LPTIM/LPTIM_Timeout/Inc/main.h Header for main.c module
- LPTIM/LPTIM_Timeout/Src/stm32wbxx_it.c Interrupt handlers
- LPTIM/LPTIM_Timeout/Src/main.c Main program
- LPTIM/LPTIM_Timeout/Src/stm32wbxx_hal_msp.c HAL MSP module
- LPTIM/LPTIM_Timeout/Src/system_stm32wbxx.c STM32WBxx system source file
@par Hardware and Software environment
- This example runs on STM32WB55xx devices.
- This example has been tested with STMicroelectronics P-NUCLEO-WB55
board and can be easily tailored to any other supported device
and development board.
- Connect an external trigger (ETR) to PC3(pin 36 in CN7 connector).
If the trigger is higher than 1Hz, the counter is regularly reset, the system stays in STOP mode.
If the trigger is lower than 1Hz, the counter expires and the system is woken up.
@par How to use it ?
In order to make the program work, you must do the following :
- Open your preferred tool chain
- Rebuild all files and load your image into target memory
- Run the example
* <h3><center>© COPYRIGHT STMicroelectronics</center></h3>
*/
|
