102 lines
4.3 KiB
Plaintext
102 lines
4.3 KiB
Plaintext
/**
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@page LPTIM_PWMExternalClock LPTIM PWM External clock example
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@verbatim
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******************************************************************************
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* @file LPTIM/LPTIM_PWMExternalClock/readme.txt
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* @author MCD Application Team
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* @brief Description of the LPTIM PWM with an External clock example.
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******************************************************************************
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*
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* Copyright (c) 2020 STMicroelectronics. All rights reserved.
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*
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* This software component is licensed by ST under BSD 3-Clause license,
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* the "License"; You may not use this file except in compliance with the
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* License. You may obtain a copy of the License at:
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* opensource.org/licenses/BSD-3-Clause
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*
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******************************************************************************
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@endverbatim
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@par Example Description
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How to configure and use, through the HAL LPTIM API, the LPTIM peripheral using an external counter clock,
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to generate a PWM signal at the lowest power consumption.
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At the beginning of the main program the HAL_Init() function is called to reset
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all the peripherals, initialize the Flash interface and the systick.
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The SystemClock_Config() function is used to configure the system clock for STM32WL55JCIx Devices :
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The CPU at 48 MHz
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The Autorelaod equal to 99 so the output frequency (OutputFrequency) will
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be equal to the external counter clock (InputFrequency) divided by (99+1).
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OutputFrequency = InputFrequency / (Autoreload + 1)
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= InputFrequency / 100
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Pulse value equal to 49 and the duty cycle (DutyCycle) is computed as follow:
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DutyCycle = 1 - [(PulseValue + 1)/ (Autoreload + 1)]
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DutyCycle = 50%
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To minimize the power consumption, after starting generating the PWM signal,
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the MCU enters in STOP mode. Note that GPIOs are configured in Low Speed to
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lower the consumption.
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User push-button (B1) pin (PA.00)is configured as input with external interrupt (External line 0),
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falling edge. When User push-button (B1) is pressed, wakeup event is generated and PWM signal
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generation is stopped.
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@note This example can not be used in DEBUG mode, this is due to the fact
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that the Cortex-M4 core is no longer clocked during low power mode
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so debugging features are disabled.
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@note Care must be taken when using HAL_Delay(), this function provides accurate
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delay (in milliseconds) based on variable incremented in SysTick ISR. This
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implies that if HAL_Delay() is called from a peripheral ISR process, then
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the SysTick interrupt must have higher priority (numerically lower)
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than the peripheral interrupt. Otherwise the caller ISR process will be blocked.
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To change the SysTick interrupt priority you have to use HAL_NVIC_SetPriority() function.
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@note This example needs to ensure that the SysTick time base is always set to 1 millisecond
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to have correct HAL operation.
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@par Keywords
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Timer, Low Power, PWM, Stop mode, Interrupt, External Clock, Output, Duty Cycle
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@par Directory contents
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- LPTIM/LPTIM_PWMExternalClock/Inc/stm32wlxx_nucleo_conf.h BSP configuration file
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- LPTIM/LPTIM_PWMExternalClock/Inc/stm32wlxx_hal_conf.h HAL configuration file
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- LPTIM/LPTIM_PWMExternalClock/Inc/stm32wlxx_it.h Interrupt handlers header file
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- LPTIM/LPTIM_PWMExternalClock/Inc/main.h Header for main.c module
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- LPTIM/LPTIM_PWMExternalClock/Src/stm32wlxx_it.c Interrupt handlers
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- LPTIM/LPTIM_PWMExternalClock/Src/main.c Main program
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- LPTIM/LPTIM_PWMExternalClock/Src/stm32wlxx_hal_msp.c HAL MSP module
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- LPTIM/LPTIM_PWMExternalClock/Src/system_stm32wlxx.c STM32WLxx system source file
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@par Hardware and Software environment
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- This example runs on STM32WL55JCIx devices.
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- This example has been tested with STMicroelectronics NUCLEO-WL55JC RevC
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board and can be easily tailored to any other supported device
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and development board.
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- Connect a clock signal to PC0 (pin 14 in CN10 connector).
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- Connect PC1 (pin 23 in CN10 connector) to an oscilloscope
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to monitor the LPTIM output waveform.
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@par How to use it ?
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In order to make the program work, you must do the following :
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- Open your preferred tool chain
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- Rebuild all files and load your image into target memory
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- Run the example
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* <h3><center>© COPYRIGHT STMicroelectronics</center></h3>
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*/
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