/**
  @page TIM_PWMOutput_Init TIM example
  
  @verbatim
  ******************** (C) COPYRIGHT 2017 STMicroelectronics *******************
  * @file    Examples_LL/TIM/TIM_PWMOutput_Init/readme.txt 
  * @author  MCD Application Team
  * @brief   Description of the TIM_PWMOutput_Init 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
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  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
  ******************************************************************************
  @endverbatim

@par Example Description

This example describes how to use a timer peripheral to generate a 
PWM output signal and update PWM duty cycle; 
Example using the STM32F2xx TIM LL API, 
peripheral initialization done using LL initialization function
to demonstrate LL init usage.

In this example TIM3 input clock (TIM3CLK) frequency is set to APB1 clock (PCLK1),
since APB1 pre-scaler is equal to 2 and it is twice PCLK1.
TIM3CLK = 2*PCLK1
PCLK1 = HCLK/2
=> TIM3CLK = (2/2)*HCLK = SystemCoreClock (120Mhz)

To set the TIM3 counter clock frequency to 10 KHz, the pre-scaler (PSC) is
calculated as follows:
PSC = (TIM3CLK / TIM3 counter clock) - 1
PSC = (SystemCoreClock /10 KHz) - 1

SystemCoreClock is set to 120 MHz for STM32F2xx Devices.

Auto-reload (ARR) is calculated to get a time base period of 10 ms,
meaning a time base frequency of 100 Hz.
ARR = (TIM3 counter clock / time base frequency) - 1
ARR = (TIM3 counter clock / 100) - 1

Initially, the capture/compare register (CCR3) 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 = (CCR3 / ARR) * 100

The timer output channel is mapped on the pin PB.0 (connected to LED1 on board
NUCLEO-F207ZG). Thus LED1 status (on/off) mirrors the timer output
level (active v.s. inactive).

Key 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 LED1 is not toggling. In fact, if the dutycycle is 0% so the LED1 is OFF. When pushing 
successively the user button, the LED1 is ON and its luminosity rises as the dutycycle value keep 
increasing.

@par Directory contents 

  - TIM/TIM_PWMOutput_Init/Inc/stm32f2xx_it.h          Interrupt handlers header file
  - TIM/TIM_PWMOutput_Init/Inc/main.h                  Header for main.c module
  - TIM/TIM_PWMOutput_Init/Inc/stm32_assert.h          Template file to include assert_failed function
  - TIM/TIM_PWMOutput_Init/Src/stm32f2xx_it.c          Interrupt handlers
  - TIM/TIM_PWMOutput_Init/Src/main.c                  Main program
  - TIM/TIM_PWMOutput_Init/Src/system_stm32f2xx.c      STM32F2xx system source file


@par Hardware and Software environment

  - This example runs on STM32F207xx devices.
    
  - This example has been tested with NUCLEO-F207ZG 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>
 */
