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92 lines
3.5 KiB
Plaintext
92 lines
3.5 KiB
Plaintext
/**
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@page TIM_DMABurst TIM DMA Burst example
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@verbatim
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******************** (C) COPYRIGHT 2017 STMicroelectronics *******************
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* @file TIM/TIM_DMABurst/readme.txt
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* @author MCD Application Team
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* @brief Description of the TIM DMA Burst 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 shows how to update the TIM1 channel1 period and the duty cycle
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using the TIM1 DMA burst feature.
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Every update DMA request, the DMA will do 3 transfers of half words into Timer
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registers beginning from ARR register.
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On the DMA update request, 0x0FFF will be transferred into ARR, 0x0000
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will be transferred into RCR, 0x0555 will be transferred into CCR1.
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The TIM1CLK frequency is set to SystemCoreClock (Hz), to get TIM1 counter
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clock at 20 MHz the Prescaler is computed as following:
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- Prescaler = (TIM1CLK / TIM1 counter clock) - 1
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SystemCoreClock is set to 180 MHz.
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The TIM1 Frequency = TIM1 counter clock/(ARR + 1)
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= 20 MHz / 4096 = 4.88 KHz
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The TIM1 CCR1 register value is equal to 0x555, so the TIM1 Channel 1 generates a
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PWM signal with a frequency equal to 4.88 KHz and a duty cycle equal to 33.33%:
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TIM1 Channel1 duty cycle = (TIM1_CCR1/ TIM1_ARR + 1)* 100 = 33.33%
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The PWM waveform can be displayed using an oscilloscope.
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@note Care must be taken when using HAL_Delay(), this function provides accurate delay (in milliseconds)
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based on variable incremented in SysTick ISR. This implies that if HAL_Delay() is called from
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a peripheral ISR process, then the SysTick interrupt must have higher priority (numerically lower)
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than the peripheral interrupt. Otherwise the caller ISR process will be blocked.
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To change the SysTick interrupt priority you have to use HAL_NVIC_SetPriority() function.
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@note The application needs 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, Burst mode, Duty Cycle, Waveform, Oscilloscope, Output, Signal, PWM
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@par Directory contents
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- TIM/TIM_DMABurst/system_stm32f4xx.c STM32F4xx system clock configuration file
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- TIM/TIM_DMABurst/stm32f4xx_hal_conf.h HAL configuration file
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- TIM/TIM_DMABurst/stm32f4xx_it.h Interrupt handlers header file
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- TIM/TIM_DMA/stm32f4xx_it.c Interrupt handlers
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- TIM/TIM_DMABurst/main.c Main program
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- TIM/TIM_DMABurst/main.h Main program header file
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@par Hardware and Software environment
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- This example runs on STM32F429xx/STM32F439xx devices.
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- This example has been tested with STMicroelectronics STM324x9I-EVAL RevB
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evaluation boards and can be easily tailored to any other supported device and development board
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- STM324x9I-EVAL RevB Set-up
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- Connect the following pins to an oscilloscope to monitor the different
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waveforms:
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- TIM1 CH1 (PA.08)
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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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