STM32CubeF7/Projects/STM32756G_EVAL/Examples/TIM/TIM_DMA

/**
  @page TIM_DMA TIM DMA example
  
  @verbatim
  ******************************************************************************
  * @file    TIM/TIM_DMA/readme.txt 
  * @author  MCD Application Team
  * @brief   Description of the TIM DMA example.
  ******************************************************************************
  * @attention
  *
  * Copyright (c) 2016 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 

Use of the DMA with TIMER Update request 
to transfer data from memory to TIMER Capture Compare Register 3 (TIM2_CCR3).

  The following configuration values are used in this example:

    - TIM2CLK = SystemCoreClock
    - Counter repetion = 3 
    - Prescaler = 0 
    - TIM2 counter clock = SystemCoreClock
    - SystemCoreClock is set to 216 MHz for STM32F7xx

  The objective is to configure TIM2 channel 3 to generate complementary PWM 
  (Pulse Width Modulation) signal with a frequency equal to 17.57 KHz, and a variable 
  duty cycle that is changed by the DMA after a specific number of Update DMA request.

  The number of this repetitive requests is defined by the TIM2 Repetition counter,
  each 4 Update Requests, the TIM2 Channel 3 Duty Cycle changes to the next new 
  value defined by the aCCValue_Buffer.
  
The PWM waveform can be displayed using an oscilloscope.

In nominal mode (except at start) , it should looks like this :
  
     .   .   .   .   .   .   .   .   .   .   .   .   .   .   .   .   .   .   
      ___________     _______         ___             ___________    __
    _|           |___|       |_______|   |___________|           |__|             
     <----57us -----><----57us -----><----57us -----><----57us ----->


@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)
      
@note The application need to ensure that the SysTick time base is always set to 1 millisecond
      to have correct HAL operation.

@par Keywords

Timers, DMA, PWM, Frequency, Duty Cycle, Waveform, Oscilloscope, Output, Signal

@Note<74>If the user code size exceeds the DTCM-RAM size or starts from internal cacheable memories (SRAM1 and SRAM2),that is shared between several processors,
 <20><><A0><A0><A0>then it is highly recommended to enable the CPU cache and maintain its coherence at application level.
<0A><><A0><A0><A0><A0>The address and the size of cacheable buffers (shared between CPU and other masters)  must be properly updated to be aligned to cache line size (32 bytes).

@Note It is recommended to enable the cache and maintain its coherence, but depending on the use case
<0A><><A0><A0><A0> It is also possible to configure the MPU as "Write through", to guarantee the write access coherence.
<0A><><A0><A0><A0><A0>In that case, the MPU must be configured as Cacheable/Bufferable/Not Shareable.
<0A><><A0><A0><A0><A0>Even though the user must manage the cache coherence for read accesses.
<0A><><A0><A0><A0><A0>Please refer to the AN4838 <20>Managing memory protection unit (MPU) in STM32 MCUs<55>
<0A><><A0><A0><A0><A0>Please refer to the AN4839 <20>Level 1 cache on STM32F7 Series<65>

@par Directory contents 

  - TIM/TIM_DMA/Inc/stm32f7xx_hal_conf.h    HAL configuration file
  - TIM/TIM_DMA/Inc/stm32f7xx_it.h          Interrupt handlers header file
  - TIM/TIM_DMA/Inc/main.h                  Header for main.c module  
  - TIM/TIM_DMA/Src/stm32f7xx_it.c          Interrupt handlers
  - TIM/TIM_DMA/Src/main.c                  Main program
  - TIM/TIM_DMA/Src/stm32f7xx_hal_msp.c     HAL MSP file
  - TIM/TIM_DMA/Src/system_stm32f7xx.c      STM32F7xx system source file

@par Hardware and Software environment

  - This example runs on STM32F756xx/STM32F746xx devices.
    
  - This example has been tested with STMicroelectronics STM327x6G-EVAL revB 
    board and can be easily tailored to any other supported device 
    and development board.

  - STM327x6G-EVAL revB Set-up
    - Connect the TIM2 pin to an oscilloscope to monitor the different waveforms: 
      - TIM2 CH3 (PB.10)

@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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