/**
  @page TIM_PWMInput TIM PWM Input example
  
  @verbatim
  ******************** (C) COPYRIGHT 2016 STMicroelectronics *******************
  * @file    TIM/TIM_PWMInput/readme.txt 
  * @author  MCD Application Team
  * @version V1.0.0
  * @date    14-April-2017
  * @brief   Description of the TIM PWM_Input example.
  ******************************************************************************
  *
  * Redistribution and use in source and binary forms, with or without modification,
  * are permitted provided that the following conditions are met:
  *   1. Redistributions of source code must retain the above copyright notice,
  *      this list of conditions and the following disclaimer.
  *   2. Redistributions in binary form must reproduce the above copyright notice,
  *      this list of conditions and the following disclaimer in the documentation
  *      and/or other materials provided with the distribution.
  *   3. Neither the name of STMicroelectronics nor the names of its contributors
  *      may be used to endorse or promote products derived from this software
  *      without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
  ******************************************************************************
  @endverbatim

@par Example Description 

Use of the TIM peripheral to measure an external signal frequency and 
duty cycle.

The TIM3CLK frequency is set to SystemCoreClock/1 (Hz), the Prescaler is 0 so the 
counter clock is SystemCoreClock/1 (Hz).
SystemCoreClock is set to 72 MHz for STM32F103xB Devices.

TIM3 is configured in PWM Input Mode: the external signal is connected to 
TIM3 Channel2 used as input pin.
To measure the frequency and the duty cycle, we use the TIM3 CC2 interrupt request,
so in the TIM3_IRQHandler routine, the frequency and the duty cycle of the external 
signal are computed.

"uwFrequency" variable contains the external signal frequency:
TIM3 counter clock = SystemCoreClock/1,
uwFrequency = TIM3 counter clock / TIM3_CCR2 in Hz, 

"uwDutyCycle" variable contains the external signal duty cycle:
uwDutyCycle = (TIM3_CCR1*100)/(TIM3_CCR2) in %.

The minimum frequency value to measure is (TIM3 counter clock / CCR MAX)
                                         = (72 MHz/1)/ 65535
                                         = 1099 Hz

TIM2 can be used to generate the external signal in case a function generator 
is not available. TIM2 is configured in PWM Output Mode to produce a square wave on PA.00.
Frequency and duty cycles can be changed by pressing the User Button (PC13).
Six combinatins are available (see thables aFrequency[] and aDutyCycle[]).

@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 Directory contents 

  - TIM/TIM_PWMInput/Inc/stm32f1xx_hal_conf.h    HAL configuration file
  - TIM/TIM_PWMInput/Inc/stm32f1xx_it.h          Interrupt handlers header file
  - TIM/TIM_PWMInput/Inc/main.h                  Header for main.c module  
  - TIM/TIM_PWMInput/Src/stm32f1xx_it.c          Interrupt handlers
  - TIM/TIM_PWMInput/Src/main.c                  Main program
  - TIM/TIM_PWMInput/Src/stm32f1xx_hal_msp.c     HAL MSP file
  - TIM/TIM_PWMInput/Src/system_stm32f1xx.c      STM32F1xx system source file


@par Hardware and Software environment

  - This example runs on STM32F103xB devices.
    
  - This example has been tested with STMicroelectronics STM32F103RB-Nucleo 
    board and can be easily tailored to any other supported device 
    and development board.

  - STM32F103RB-Nucleo Set-up
    - You can either Connect the external signal to measure to the TIM3 CH2 pin (PA.07) (pin 4 in CN5 connector).
    - Or connect TIM3 CH1 pin PA.00 (pin 1 in CN8 connector) to the TIM3 CH2 pin (PA.07) instead of an external signal.

	
@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>&copy; COPYRIGHT STMicroelectronics</center></h3>
 */
