102 lines
4.6 KiB
Plaintext
102 lines
4.6 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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* @attention
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*
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* Copyright (c) 2016 STMicroelectronics.
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* All rights reserved.
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*
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* This software is licensed under terms that can be found in the LICENSE file
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* in the root directory of this software component.
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* If no LICENSE file comes with this software, it is provided AS-IS.
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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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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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Wkup/Tamper push-button pin (PC.13)is configured as input with external interrupt (EXTI_Line10-15),
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falling edge. When Wkup/Tamper push-button is pressed, wakeup event is generated and PWM signal
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generation is stopped.
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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 The application need 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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@Note<74>If the user code size exceeds the DTCM-RAM size or starts from internal cacheable memories (SRAM1 and SRAM2),that is shared between several processors,
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<20><><EFBFBD><EFBFBD><EFBFBD>then it is highly recommended to enable the CPU cache and maintain its coherence at application level.
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<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>The address and the size of cacheable buffers (shared between CPU and other masters) must be properly updated to be aligned to cache line size (32 bytes).
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@Note It is recommended to enable the cache and maintain its coherence, but depending on the use case
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<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> It is also possible to configure the MPU as "Write through", to guarantee the write access coherence.
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<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>In that case, the MPU must be configured as Cacheable/Bufferable/Not Shareable.
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<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Even though the user must manage the cache coherence for read accesses.
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<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Please refer to the AN4838 <20>Managing memory protection unit (MPU) in STM32 MCUs<55>
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<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Please refer to the AN4839 <20>Level 1 cache on STM32F7 Series<65>
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@par Directory contents
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- LPTIM/LPTIM_PWMExternalClock/Inc/stm32f7xx_hal_conf.h HAL configuration file
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- LPTIM/LPTIM_PWMExternalClock/Inc/stm32f7xx_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/stm32f7xx_it.c Interrupt handlers
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- LPTIM/LPTIM_PWMExternalClock/Src/main.c Main program
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- LPTIM/LPTIM_PWMExternalClock/Src/stm32f7xx_hal_msp.c HAL MSP module
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- LPTIM/LPTIM_PWMExternalClock/Src/system_stm32f7xx.c STM32F7xx system source file
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@par Hardware and Software environment
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- This example runs on STM32F769xx/STM32F779xx/STM32F777xx/STM32F767xx devices.
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- This example has been tested with STMicroelectronics STM32F769I-EVAL
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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 an external square clock signal(GBF) to PD.12.
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- Connect PD.13 to an oscilloscope 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 toolchain
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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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*/
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