/**
  @page TIM_PWM_Output TIM PWM Output example
  
  @verbatim
  ******************** (C) COPYRIGHT 2012 STMicroelectronics *******************
  * @file    TIM/PWM_Output/readme.txt 
  * @author  MCD Application Team
  * @version V1.1.1
  * @date    13-April-2012
  * @brief   Description of the TIM PWM Output example.
  ******************************************************************************
  *
  * Licensed under MCD-ST Liberty SW License Agreement V2, (the "License");
  * You may not use this file except in compliance with the License.
  * You may obtain a copy of the License at:
  *
  *        http://www.st.com/software_license_agreement_liberty_v2
  *
  * Unless required by applicable law or agreed to in writing, software 
  * distributed under the License is distributed on an "AS IS" BASIS, 
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  *
  ******************************************************************************
   @endverbatim

@par Example Description 

This example shows how to configure the TIM peripheral in PWM (Pulse Width Modulation) 
mode.

The TIM3CLK frequency is set to SystemCoreClock / 3 (Hz), to get TIM3 counter
clock at 8 MHz the Prescaler is computed as following:
   - Prescaler = (TIM3CLK / TIM3 counter clock) - 1
SystemCoreClock is set to 32 MHz for Ultra Low Power Medium-Density and High-Density
Devices.

The TIM3 is running at 12 KHz: TIM3 Frequency = TIM3 counter clock/(ARR + 1)
                                              = 8 MHz / 666 = 12 KHz
The TIM3 CCR1 register value is equal to 333, so the TIM3 Channel 1 generates a 
PWM signal with a frequency equal to 12 KHz and a duty cycle equal to 50%:
TIM3 Channel1 duty cycle = (TIM3_CCR1/ TIM3_ARR + 1)* 100 = 50%

The TIM3 CCR2 register value is equal to 249, so the TIM3 Channel 2 generates a 
PWM signal with a frequency equal to 12 KHz and a duty cycle equal to 37.5%:
TIM3 Channel2 duty cycle = (TIM3_CCR2/ TIM3_ARR + 1)* 100 = 37.5%

The TIM3 CCR3 register value is equal to 166, so the TIM3 Channel 3 generates a 
PWM signal with a frequency equal to 12 KHz and a duty cycle equal to 25%:
TIM3 Channel3 duty cycle = (TIM3_CCR3/ TIM3_ARR + 1)* 100 = 25%

The TIM3 CCR4 register value is equal to 83, so the TIM3 Channel 4 generates a 
PWM signal with a frequency equal to 12 KHz and a duty cycle equal to 12.5%:
TIM3 Channel4 duty cycle = (TIM3_CCR4/ TIM3_ARR + 1)* 100 = 12.5%

The PWM waveform can be displayed using an oscilloscope.

@par Directory contents 

  - TIM/PWM_Output/stm32l1xx_conf.h    Library Configuration file
  - TIM/PWM_Output/stm32l1xx_it.c      Interrupt handlers
  - TIM/PWM_Output/stm32l1xx_it.h      Interrupt handlers header file
  - TIM/PWM_Output/main.c              Main program
  - TIM/PWM_Output/system_stm32l1xx.c  STM32L1xx system source file

@note The "system_stm32l1xx.c" is generated by an automatic clock configuration 
      system and can be easily customized to your own configuration. 
      To select different clock setup, use the "STM32L1xx_Clock_Configuration_V1.1.0.xls" 
      provided with the AN3309 package available on <a href="http://www.st.com/internet/mcu/family/141.jsp">  ST Microcontrollers </a>
 
@par Hardware and Software environment 

  - This example runs on STM32L1xx Ultra Low Power High-, Medium-Density and Medium-Density Plus Devices.
  
  - This example has been tested with STMicroelectronics STM32L152D-EVAL (STM32L1xx 
    Ultra Low Power High-Density) and STM32L152-EVAL (STM32L1xx Ultra Low 
    Power Medium-Density) evaluation board and can be easily tailored to any 
    other supported device and development board.

  - STM32L152-EVAL and STM32L152D-EVAL Set-up 
    - Connect the following pins(TIM3 full remapping pins) to an oscilloscope to monitor the different 
      waveforms:
        - PA.06: (TIM3_CH1)
        - PA.07: (TIM3_CH2)
        - PB.00: (TIM3_CH3)
        - PB.01: (TIM3_CH4) 

@par How to use it ? 

In order to make the program work, you must do the following :
 - Copy all source files from this example folder to the template folder under
   Project\STM32L1xx_StdPeriph_Templates
 - Open your preferred toolchain 
 - Rebuild all files and load your image into target memory
 - Run the example

@note
- Ultra Low Power Medium-density devices are STM32L151xx and STM32L152xx 
  microcontrollers where the Flash memory density ranges between 64 and 128 Kbytes.
- Ultra Low Power Medium-density Plus devices are STM32L151xx, STM32L152xx and 
  STM32L162xx microcontrollers where the Flash memory density is 256 Kbytes.
- Ultra Low Power High-density devices are STM32L151xx, STM32L152xx and STM32L162xx 
  microcontrollers where the Flash memory density is 384 Kbytes.  
   
 * <h3><center>&copy; COPYRIGHT STMicroelectronics</center></h3>
 */


