/**
  @page TIM_PWM_Input TIM PWM Input example
  
  @verbatim
  ******************** (C) COPYRIGHT 2012 STMicroelectronics *******************
  * @file    TIM/PWM_Input/readme.txt 
  * @author  MCD Application Team
  * @version V1.1.1
  * @date    13-April-2012
  * @brief   Description of the TIM PWM Input 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 use the TIM peripheral to measure the frequency and 
duty cycle of an external signal.

The TIMxCLK frequency is set to SystemCoreClock (Hz), the Prescaler is 0 so the 
TIM3 counter clock is SystemCoreClock (Hz).
SystemCoreClock is set to 32 MHz for Ultra Low Power Medium-Density and High-Density
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. 
The "Frequency" variable contains the external signal frequency:
Frequency = TIM3 counter clock / TIM3_CCR2 in Hz, 
The "DutyCycle" variable contains the external signal duty cycle:
DutyCycle = (TIM3_CCR1*100)/(TIM3_CCR2) in %.

For Ultra Low Power Medium-Density and High-Density Devices,the minimum frequency
value to measure is 488 Hz. 

@par Directory contents 

  - TIM/PWM_Input/stm32l1xx_conf.h    Library Configuration file
  - TIM/PWM_Input/stm32l1xx_it.c      Interrupt handlers
  - TIM/PWM_Input/stm32l1xx_it.h      Interrupt handlers header file
  - TIM/PWM_Input/main.c              Main program
  - TIM/PWM_Input/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 external signal to measure to the TIM3 CH2 pin (PA.07).  
        
@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>
 */


