STM32CubeF4/Projects/STM32469I_EVAL/Examples/TIM/TIM_PrescalerSelection/readme.txt

/**
  @page TIM_PrescalerSelection TIM Prescaler Selection example
  
  @verbatim
  ******************** (C) COPYRIGHT 2017 STMicroelectronics *******************
  * @file    TIM/TIM_PrescalerSelection/readme.txt 
  * @author  MCD Application Team
  * @brief   Description of the PWM signals generation using TIM3
  ******************************************************************************
  *
  * 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
  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
  ******************************************************************************
  @endverbatim

@par Example Description 

This example shows how to configure the TIM peripheral in PWM (Pulse Width Modulation) 
mode with clock prescaler selection feature activated using __HAL_RCC_TIMCLKPRESCALER()
which allows to double the output frequency.

SystemCoreClock is set to 180 MHz for STM32F4xx Devices.

  In this example TIM3 input clock (TIM3CLK) is set to 4 * APB1 clock (PCLK1), since 
  Timer clock prescalers selection activated (TIMPRE bit from RCC_DCKCFGR register is set).   
  TIM3CLK = 4 * PCLK1  
  PCLK1 = HCLK / 4 
  => TIM3CLK = HCLK = SystemCoreClock

  For TIM3CLK equal to SystemCoreClock and prescaler equal to (5 - 1), TIM3 counter clock 
  is computed as follows:
  TIM3 counter clock = TIM3CLK / (Prescaler + 1)
                     = SystemCoreClock / (Prescaler + 1)
                     = 36MHz

  For ARR equal to (1800 - 1), the TIM3 output clock is computed as follows:
  TIM3 output clock = TIM3 counter clock / (ARR + 1)
                    = 20KHZ
                     
  The TIM3 CCR1 register value is equal to 900, so the TIM3 Channel 1 generates a 
  PWM signal with a frequency equal to 20 KHz and a duty cycle equal to 50%:

  TIM3 Channel1 duty cycle = (TIM3_CCR1/ TIM3_ARR + 1)* 100 = 50%


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.

@note The connection of the LCD reset pin to a dedicated GPIO PK7 instead of the STM32F469 NRST pin may cause residual display on LCD with applications/examples that do not require display.
	  The LCD clear can be ensured by hardware through the board's power off/power on or by software calling the BSP_LCD_Reset() function.

@par Directory contents 

  - TIM/TIM_PrescalerSelection/Inc/stm32f4xx_hal_conf.h    HAL configuration file
  - TIM/TIM_PrescalerSelection/Inc/stm32f4xx_it.h          Interrupt handlers header file
  - TIM/TIM_PrescalerSelection/Inc/main.h                  Header for main.c module  
  - TIM/TIM_PrescalerSelection/Src/stm32f4xx_it.c          Interrupt handlers
  - TIM/TIM_PrescalerSelection/Src/main.c                  Main program
  - TIM/TIM_PrescalerSelection/Src/stm32f4xx_hal_msp.c     HAL MSP file
  - TIM/TIM_PrescalerSelection/Src/system_stm32f4xx.c      STM32F4xx system source file


@par Hardware and Software environment

  - This example runs on STM32F469xx/STM32F479xx devices.

  - This example has been tested and validated with STMicroelectronics STM32469I-EVAL RevC 
    board and can be easily tailored to any other supported device 
    and development board.      

  - STM32469I-EVAL Set-up
   Connect the following pins to an oscilloscope to monitor the different waveforms:
        - TIM3_CH1 : PB.04, pin 24 in CN6 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

 * <h3><center>&copy; COPYRIGHT STMicroelectronics</center></h3>
 */