/**
  @page TIM_PWMOutput TIM PWM Output example
  
  @verbatim
  ******************** (C) COPYRIGHT 2017 STMicroelectronics *******************
  * @file    TIM/TIM_PWMOutput/readme.txt 
  * @author  MCD Application Team
  * @brief   Description of the PWM signals generation using TIM4
  ******************************************************************************
  * @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 configure the TIM peripheral in PWM (Pulse Width Modulation) 
mode.

SystemCoreClock is set to 100 MHz for STM32F4xx Devices.

    In this example TIM4 input clock (TIM4CLK) is set to APB1 clock x 2,
    since APB1 prescaler is equal to 2.
      TIM4CLK = APB1CLK*2
      APB1CLK = HCLK/2
      => TIM4CLK = HCLK = SystemCoreClock

    To get TIM4 counter clock at 16 MHz, the prescaler is computed as follows:
       Prescaler = (TIM4CLK / TIM4 counter clock) - 1
       Prescaler = ((SystemCoreClock) /16 MHz) - 1

    To get TIM4 output clock at 24 KHz, the period (ARR)) is computed as follows:
       ARR = (TIM4 counter clock / TIM4 output clock) - 1
           = 665

    TIM4 Channel1 duty cycle = (TIM4_CCR1/ TIM4_ARR + 1)* 100 = 50%
    TIM4 Channel2 duty cycle = (TIM4_CCR2/ TIM4_ARR + 1)* 100 = 37.5%
    TIM4 Channel3 duty cycle = (TIM4_CCR3/ TIM4_ARR + 1)* 100 = 25%
    TIM4 Channel4 duty cycle = (TIM4_CCR4/ TIM4_ARR + 1)* 100 = 12.5%


The PWM waveforms can be displayed using an oscilloscope.

@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, Output, signal, PWM, Oscilloscope, Frequency, Duty cycle, Waveform

@par Directory contents 

  - TIM/TIM_PWMOutput/Inc/stm32f4xx_hal_conf.h    HAL configuration file
  - TIM/TIM_PWMOutput/Inc/stm32f4xx_it.h          Interrupt handlers header file
  - TIM/TIM_PWMOutput/Inc/main.h                  Header for main.c module  
  - TIM/TIM_PWMOutput/Src/stm32f4xx_it.c          Interrupt handlers
  - TIM/TIM_PWMOutput/Src/main.c                  Main program
  - TIM/TIM_PWMOutput/Src/stm32f4xx_hal_msp.c     HAL MSP file
  - TIM/TIM_PWMOutput/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 following pins to an oscilloscope to monitor the different waveforms:
        - TIM4_CH1 : PB.06 (pin 23 in P2 connector)
        - TIM4_CH2 : PB.07 (pin 24 in P2 connector)
        - TIM4_CH3 : PB.08 (pin 19 in P2 connector)
        - TIM4_CH4 : PB.09 (pin 20 in P2 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


 */