/**
  @page TIM_PWMOutput TIM example
  
  @verbatim
  ******************** (C) COPYRIGHT 2016 STMicroelectronics *******************
  * @file    Examples_LL/TIM/TIM_PWMOutput/readme.txt 
  * @author  MCD Application Team
  * @brief   Description of the TIM_PWMOutput example.
  ******************************************************************************
  * @attention
  *
  * <h2><center>&copy; Copyright (c) 2016 STMicroelectronics.
  * All rights reserved.</center></h2>
  *
  * 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

Use of a timer peripheral to generate a 
PWM output signal and update the PWM duty cycle. This example is based on the 
STM32F0xx TIM LL API. The peripheral initialization uses 
LL unitary service functions for optimization purposes (performance and size).

In this example TIM2 input clock TIM2CLK is set to APB1 clock (PCLK1),
since APB1 pre-scaler is equal to 1.
    TIM2CLK = PCLK1
    PCLK1 = HCLK
    => TIM2CLK = HCLK = SystemCoreClock (48 MHz)

To set the TIM2 counter clock frequency to 10 KHz, the pre-scaler (PSC) is
calculated as follows:
PSC = (TIM2CLK / TIM2 counter clock) - 1
PSC = (SystemCoreClock /10 KHz) - 1

SystemCoreClock is set to 48 MHz for STM32F0xx Devices.

Auto-reload (ARR) is calculated to get a time base period of 10 ms,
meaning a time base frequency of 100 Hz.
ARR = (TIM2 counter clock / time base frequency) - 1
ARR = (TIM2 counter clock / 100) - 1

Initially, the capture/compare register (CCR1) of the output channel is set to
half the auto-reload value meaning a initial duty cycle of 50%.
Generally speaking this duty cycle is calculated as follows:
Duty cycle = (CCR1 / ARR) * 100

The timer output channel is mapped on the pin PA.05 (connected to LED2 on board
STM32F072RB-Nucleo RevC). Thus LED2 status (on/off) mirrors the timer output
level (active v.s. inactive).

User push-button can be used to change the duty cycle from 0% up to 100% by
steps of 10%. Duty cycle is periodically measured. It can be observed through
the debugger by watching the variable uwMeasuredDutyCycle.

Initially the output channel is configured in output compare toggle mode.
@note The LED2 is not toggling. In fact, if the dutycycle is 0% so the LED2 is OFF. When pushing 
successively the user button, the LED2 is ON and its luminosity rises as the dutycycle value keep 
increasing.

@par Directory contents 

  - TIM/TIM_PWMOutput/Inc/stm32f0xx_it.h          Interrupt handlers header file
  - TIM/TIM_PWMOutput/Inc/main.h                  Header for main.c module
  - TIM/TIM_PWMOutput/Inc/stm32_assert.h          Template file to include assert_failed function
  - TIM/TIM_PWMOutput/Src/stm32f0xx_it.c          Interrupt handlers
  - TIM/TIM_PWMOutput/Src/main.c                  Main program
  - TIM/TIM_PWMOutput/Src/system_stm32f0xx.c      STM32F0xx system source file


@par Hardware and Software environment

  - This example runs on STM32F072xB devices.
    
  - This example has been tested with STM32F072RB-Nucleo RevC board and can be
    easily tailored to any other supported device and development board.


@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>
 */
