STM32CubeF4/Projects/STM32F412G-Discovery/Examples/TIM/TIM_DMA/readme.txt

/**
  @page TIM_DMA TIM DMA example
  
  @verbatim
  ******************** (C) COPYRIGHT 2017 STMicroelectronics *******************
  * @file    TIM/TIM_DMA/readme.txt 
  * @author  MCD Application Team
  * @brief   Description of the TIM DMA example.
  ******************************************************************************
  *
  * Copyright (c) 2017 STMicroelectronics. All rights reserved.
  *
  * This software component is licensed by ST under BSD 3-Clause license,
  * the "License"; You may not use this file except in compliance with the
  * License. You may obtain a copy of the License at:
  *                       opensource.org/licenses/BSD-3-Clause
  *
  ******************************************************************************
   @endverbatim

@par Example Description 

This example provides a description of how to use DMA with TIMER Update request
to transfer Data from memory to TIMER Capture Compare Register 3 (CCR3).

  The following configuration values are used in this example:

    - TIM3CLK = SystemCoreClock
    - Counter repetition = 3 
    - Prescaler = 0 
    - TIM3 counter clock = SystemCoreClock
    - SystemCoreClock is set to 100 MHz for STM32F4xx

  The objective is to configure TIM3 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 TIM3 Repetition counter,
  each 4 Update Requests, the TIM3 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 PWM signal frequency value mentioned above is theoretical (obtained when the system clock frequency 
      is exactly 100 MHz). Since the generated system clock frequency may vary from one board to another observed
      PWM signal frequency might be slightly different.
	  
@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

@par Directory contents 

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

@par Hardware and Software environment

  - This example runs on STM32F412xG devices.
  - In this example, the clock is set to 100 MHz.
    
  - This example has been tested with STMicroelectronics STM32412G-DISCOVERY 
    board and can be easily tailored to any other supported device 
    and development board.

  - STM32412G-DISCOVERY Set-up
    - Connect the TIM3 pin to an oscilloscope to monitor the different waveforms: 
    - TIM3 CH3 (PB.00) (pin 22 in connector P1).

@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>
 */