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/**
@page TIM_InputCapture Input Capture example
@verbatim
******************************************************************************
* @file TIM/TIM_InputCapture/readme.txt
* @author MCD Application Team
* @brief Description of the TIM_InputCapture example.
******************************************************************************
*
* Copyright (c) 2019 STMicroelectronics. All rights reserved.
*
* This software component is licensed by ST under BSD 3-Clause license,
* the "License"; You may not use this file except in compliance with the
* License. You may obtain a copy of the License at:
* opensource.org/licenses/BSD-3-Clause
*
******************************************************************************
@endverbatim
@par Example Description
How to use the TIM peripheral to measure an external signal frequency.
At the beginning of the main program the HAL_Init() function is called to reset
all the peripherals, initialize the Flash interface and the systick.
The SystemClock_Config() function is used to configure the system clock for STM32WB55RGVx Devices :
The CPU at 64 MHz
The TIM2CLK frequency is set to SystemCoreClock (Hz), the Prescaler is 0,
so the TIM2 counter clock is SystemCoreClock (Hz).
SystemCoreClock is set to 64 MHz for STM32WB55RGVx Devices.
TIM2 is configured in Input Capture Mode: the external signal is connected to
TIM2 Channel2 used as input pin.
To measure the frequency we use the TIM2 CC interrupt request, so in the
TIM2 CC IRQHandler routine, the frequency of the external signal is computed.
The "uwFrequency" variable contains the external signal frequency:
uwFrequency = TIM2 counter clock / uwDiffCapture (Hz),
where "uwDiffCapture" is the difference between two consecutive TIM2 captures.
The minimum frequency value to measure is TIM2 counter clock / CCR MAX
= (SystemCoreClock) / 65535
Due to TIM2 CC IRQHandler processing time (around 3.12us), the maximum
frequency value to measure is around 320kHz.
@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, DMA, Frequency, Input, Capture, External Signal, Measurement
@par Directory contents
- TIM/TIM_InputCapture/Inc/stm32wbxx_hal_conf.h HAL configuration file
- TIM/TIM_InputCapture/Inc/stm32wbxx_it.h Interrupt handlers header file
- TIM/TIM_InputCapture/Inc/main.h Header for main.c module
- TIM/TIM_InputCapture/Src/stm32wbxx_it.c Interrupt handlers
- TIM/TIM_InputCapture/Src/main.c Main program
- TIM/TIM_InputCapture/Src/stm32wbxx_hal_msp.c HAL MSP file
- TIM/TIM_InputCapture/Src/system_stm32wbxx.c STM32WBxx system source file
@par Hardware and Software environment
- This example runs on STM32WB55xx devices.
- In this example, the clock is set to 64 MHz.
- This example has been tested with STMicroelectronics P-NUCLEO-WB55
board and can be easily tailored to any other supported device
and development board.
- P-NUCLEO-WB55 Set-up
- Connect the external signal to measure to the TIM2 CH2 pin (PA.01 (pin 32 in CN7 connector)).
@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
* <h3><center>© COPYRIGHT STMicroelectronics</center></h3>
*/
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