103 lines
4.6 KiB
Plaintext
103 lines
4.6 KiB
Plaintext
/**
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@page TIM_PWMInput TIM PWM Input example
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@verbatim
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******************************************************************************
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* @file TIM/TIM_PWMInput/readme.txt
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* @author MCD Application Team
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* @brief Description of the TIM PWM_Input 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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Use of the TIM peripheral to measure the frequency and
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duty cycle of an external signal.
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The TIM3CLK frequency is set to SystemCoreClock (Hz), the Prescaler is 0 so the
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counter clock is SystemCoreClock (Hz).
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SystemCoreClock is set to 216 MHz for STM32F767xx/STM32F769xx/STM32F777xx/STM32F779xx Devices.
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TIM3 is configured in PWM Input Mode: the external signal is connected to
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TIM3 Channel2 used as input pin.
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To measure the frequency and the duty cycle, we use the TIM3 CC2 interrupt request,
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so in the TIM3_IRQHandler routine, the frequency and the duty cycle of the external
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signal are computed.
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"uwFrequency" variable contains the external signal frequency:
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TIM3 counter clock = SystemCoreClock / 2,
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uwFrequency = TIM3 counter clock / TIM3_CCR2 in Hz,
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"uwDutyCycle" variable contains the external signal duty cycle:
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uwDutyCycle = (TIM3_CCR1*100)/(TIM3_CCR2) in %.
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The minimum frequency value to measure is (TIM3 counter clock / CCR MAX)
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= (216 MHz) / 2 / 65535
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= 1648 Hz
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@note Care must be taken when using HAL_Delay(), this function provides accurate delay (in milliseconds)
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based on variable incremented in SysTick ISR. This implies that if HAL_Delay() is called from
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a peripheral ISR process, then 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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Timers, Input, signals, PWM, External signal, Frequency, Duty cycle, Measure
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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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- TIM/TIM_PWMInput/Inc/stm32f7xx_hal_conf.h HAL configuration file
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- TIM/TIM_PWMInput/Inc/stm32f7xx_it.h Interrupt handlers header file
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- TIM/TIM_PWMInput/Inc/main.h Header for main.c module
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- TIM/TIM_PWMInput/Src/stm32f7xx_it.c Interrupt handlers
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- TIM/TIM_PWMInput/Src/main.c Main program
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- TIM/TIM_PWMInput/Src/stm32f7xx_hal_msp.c HAL MSP file
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- TIM/TIM_PWMInput/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 STM32F767xx/STM32F769xx/STM32F777xx/STM32F779xx 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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- STM32F769I-EVAL Set-up
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- Connect the external signal to measure to the TIM3 CH2 pin (PB.05).
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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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