102 lines
4.0 KiB
Plaintext
102 lines
4.0 KiB
Plaintext
/**
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@page TIM_DMA TIM DMA example
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@verbatim
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******************** (C) COPYRIGHT 2017 STMicroelectronics *******************
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* @file TIM/TIM_DMA/readme.txt
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* @author MCD Application Team
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* @brief Description of the TIM DMA example.
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******************************************************************************
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* @attention
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*
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* Copyright (c) 2017 STMicroelectronics.
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* All rights reserved.
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*
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* This software is licensed under terms that can be found in the LICENSE file
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* in the root directory of this software component.
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* If no LICENSE file comes with this software, it is provided AS-IS.
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*
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******************************************************************************
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@endverbatim
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@par Example Description
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This example provides a description of how to use DMA with TIMER Update request
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to transfer Data from memory to TIMER Capture Compare Register 3 (CCR3).
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The following configuration values are used in this example:
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- TIM3CLK = SystemCoreClock
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- Counter repetition = 3
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- Prescaler = 0
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- TIM3 counter clock = SystemCoreClock
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- SystemCoreClock is set to 100 MHz for STM32F4xx
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The objective is to configure TIM3 channel 3 to generate complementary PWM
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(Pulse Width Modulation) signal with a frequency equal to 17.57 KHz, and a variable
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duty cycle that is changed by the DMA after a specific number of Update DMA request.
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The number of this repetitive requests is defined by the TIM3 Repetition counter,
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each 4 Update Requests, the TIM3 Channel 3 Duty Cycle changes to the next new
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value defined by the aCCValue_Buffer.
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The PWM waveform can be displayed using an oscilloscope.
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In nominal mode (except at start) , it should looks like this :
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. . . . . . . . . . . . . . . . . .
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___________ _______ ___ ___________ __
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_| |___| |_______| |___________| |__|
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<----57us -----><----57us -----><----57us -----><----57us ----->
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@note PWM signal frequency value mentioned above is theoretical (obtained when the system clock frequency
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is exactly 100 MHz). Since the generated system clock frequency may vary from one board to another observed
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PWM signal frequency might be slightly different.
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@note Care must be taken when using HAL_Delay(), this function provides accurate
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delay (in milliseconds) based on variable incremented in SysTick ISR. This
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implies that if HAL_Delay() is called from a peripheral ISR process, then
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the SysTick interrupt must have higher priority (numerically lower)
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@note The application need to ensure that the SysTick time base is always set to 1 millisecond
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to have correct HAL operation.
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@par Keywords
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Timers, DMA, PWM, Frequency, Duty Cycle, Waveform, Oscilloscope, Output, Signal
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@par Directory contents
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- TIM/TIM_DMA/Inc/stm32f4xx_hal_conf.h HAL configuration file
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- TIM/TIM_DMA/Inc/stm32f4xx_it.h Interrupt handlers header file
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- TIM/TIM_DMA/Inc/main.h Header for main.c module
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- TIM/TIM_DMA/Src/stm32f4xx_it.c Interrupt handlers
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- TIM/TIM_DMA/Src/main.c Main program
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- TIM/TIM_DMA/Src/stm32f4xx_hal_msp.c HAL MSP file
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- TIM/TIM_DMA/Src/system_stm32f4xx.c STM32F4xx system source file
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@par Hardware and Software environment
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- This example runs on STM32F412xG devices.
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- In this example, the clock is set to 100 MHz.
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- This example has been tested with STMicroelectronics STM32412G-DISCOVERY
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board and can be easily tailored to any other supported device
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and development board.
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- STM32412G-DISCOVERY Set-up
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- Connect the TIM3 pin to an oscilloscope to monitor the different waveforms:
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- TIM3 CH3 (PB.00) (pin 22 in connector P1).
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@par How to use it ?
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In order to make the program work, you must do the following :
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- Open your preferred toolchain
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- Rebuild all files and load your image into target memory
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- Run the example
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*/
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