STM32CubeF4

/**
  @page TIM_DMABurst TIM DMA Burst example

  @verbatim
  ******************** (C) COPYRIGHT 2017 STMicroelectronics *******************
  * @file    TIM/TIM_DMABurst/readme.txt 
  * @author  MCD Application Team
  * @brief   Description of the TIM DMA Burst example.
  ******************************************************************************
  * @attention
  *
  * Copyright (c) 2017 STMicroelectronics.
  * All rights reserved.
  *
  * This software is licensed under terms that can be found in the LICENSE file
  * in the root directory of this software component.
  * If no LICENSE file comes with this software, it is provided AS-IS.
  *
  ******************************************************************************
   @endverbatim

@par Example Description 

This example shows how to update the TIM1 channel1 period and the duty cycle 
using the TIM1 DMA burst feature.

Every update DMA request, the DMA will do 3 transfers of half words into Timer 
registers beginning from ARR register.
On the DMA update request, 0x0FFF will be transferred into ARR, 0x0000 
will be transferred into RCR, 0x0555 will be transferred into CCR1. 

The TIM1CLK frequency is set to SystemCoreClock (Hz), to get TIM1 counter
clock at 20 MHz the Prescaler is computed as following:
- Prescaler = (TIM1CLK / TIM1 counter clock) - 1

SystemCoreClock is set to 180 MHz.

The TIM1 Frequency = TIM1 counter clock/(ARR + 1)
                   = 20 MHz / 4096 = 4.88 KHz

The TIM1 CCR1 register value is equal to 0x555, so the TIM1 Channel 1 generates a 
PWM signal with a frequency equal to 4.88 KHz and a duty cycle equal to 33.33%:
TIM1 Channel1 duty cycle = (TIM1_CCR1/ TIM1_ARR + 1)* 100 = 33.33%

The PWM waveform 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 needs to ensure that the SysTick time base is always set to 1 millisecond
      to have correct HAL operation.

@par Keywords

Timers, DMA, Burst mode, Duty Cycle, Waveform, Oscilloscope, Output, Signal, PWM

@par Directory contents 

  - TIM/TIM_DMABurst/system_stm32f4xx.c         STM32F4xx system clock configuration file
  - TIM/TIM_DMABurst/stm32f4xx_hal_conf.h       HAL configuration file
  - TIM/TIM_DMABurst/stm32f4xx_it.h             Interrupt handlers header file
  - TIM/TIM_DMA/stm32f4xx_it.c                  Interrupt handlers
  - TIM/TIM_DMABurst/main.c                     Main program
  - TIM/TIM_DMABurst/main.h                     Main program header file


@par Hardware and Software environment

  - This example runs on STM32F429xx/STM32F439xx devices.
    
  - This example has been tested with STMicroelectronics STM324x9I-EVAL RevB 
    evaluation boards and can be easily tailored to any other supported device and development board

  - STM324x9I-EVAL RevB Set-up
    - Connect the following pins to an oscilloscope to monitor the different
      waveforms:  
        - TIM1 CH1 (PA.08) 


@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


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