/**
@page TIM_InputCapture Input Capture example
@verbatim
******************** (C) COPYRIGHT 2017 STMicroelectronics *******************
* @file TIM/TIM_InputCapture/readme.txt
* @author MCD Application Team
* @brief Description of the TIM_InputCapture example.
******************************************************************************
* @attention
*
* Copyright (c) 2017 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
This example shows how to use the TIM peripheral to measure the frequency of
an external signal.
The TIM3CLK frequency is set to SystemCoreClock (Hz), the Prescaler is 0,
so the TIM3 counter clock is SystemCoreClock (Hz).
SystemCoreClock is set to 100 MHz for STM32F412xG Devices.
TIM3 is configured in Input Capture Mode: the external signal is connected to
TIM3 Channel2 used as input pin.
To measure the frequency we use the TIM3 CC2 interrupt request, so in the
TIM3_IRQHandler routine, the frequency of the external signal is computed.
The "uwFrequency" variable contains the external signal frequency:
uwFrequency = TIM3 counter clock / uwDiffCapture (Hz),
where "uwDiffCapture" is the difference between two consecutive TIM3 captures.
The minimum frequency value to measure is TIM3 counter clock / CCR MAX
= 100 MHz / 65535
= 1,526 kHz
Due to TIM3_IRQHandler processing time (around 2.5us), the maximum
frequency value to measure is around 500kHz.
@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 The application need to ensure that the SysTick time base is always set to 1 millisecond
to have correct HAL operation.
@par Keywords
Timers, DMA, Frequency, Input, Capture, External Signal, Measurement
@par Directory contents
- TIM/TIM_InputCapture/Inc/stm32f4xx_hal_conf.h HAL configuration file
- TIM/TIM_InputCapture/Inc/stm32f4xx_it.h Interrupt handlers header file
- TIM/TIM_InputCapture/Inc/main.h Header for main.c module
- TIM/TIM_InputCapture/Src/stm32f4xx_it.c Interrupt handlers
- TIM/TIM_InputCapture/Src/main.c Main program
- TIM/TIM_InputCapture/Src/stm32f4xx_hal_msp.c HAL MSP file
- TIM/TIM_InputCapture/Src/system_stm32f4xx.c STM32F4xx system source file
@par Hardware and Software environment
- This example runs on STM32F412xG devices.
- In this example, the clock is set to 100 MHz.
- This example has been tested with STMicroelectronics STM32412G-DISCOVERY
board and can be easily tailored to any other supported device
and development board.
- STM32412G-DISCOVERY Set-up
- Connect the external signal to measure to the TIM3 CH2 pin (PB.05).
@par How to use it ?
In order to make the program work, you must do the following :
- Open your preferred toolchain
- Rebuild all files and load your image into target memory
- Run the example
*/
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