104 lines
4.8 KiB
Plaintext
104 lines
4.8 KiB
Plaintext
/**
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@page RCC_ClockConfig RCC Clock Configuration example
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@verbatim
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******************** (C) COPYRIGHT 2017 STMicroelectronics *******************
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* @file RCC/RCC_ClockConfig/readme.txt
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* @author MCD Application Team
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* @brief Description of the RCC Clock Configuration 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 describes how to use the RCC HAL API to configure the system clock (SYSCLK)
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and modify the clock settings in Run mode.
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In this example, after startup SYSCLK is configured to the max frequency using the PLL with
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HSE as clock source, the USER button (connected to EXTI Line13) will be
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used to change the PLL source: from HSE to HSI, and vice versa.
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Each time the Key button is pressed; EXTI Line13 interrupt is generated and in the ISR
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the PLL oscillator source is checked using __HAL_RCC_GET_PLL_OSCSOURCE() macro:
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1- If the HSE oscillator is selected as PLL source, the following steps will be followed to switch
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the PLL source to HSI oscillator:
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a- Switch the system clock source to HSE to allow modification of the PLL configuration
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b- Enable HSI Oscillator, select it as PLL source and finally activate the PLL
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c- Activate the Over Drive feature to reach 180 MHz as system clock frequency
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d- Select the PLL as system clock source and configure the HCLK, PCLK1 and PCLK2 clocks dividers
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e- Disable the HSE oscillator (optional, if the HSE is no more needed by the application)
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2- If the HSI oscillator is selected as PLL source, the following steps will be followed to switch
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the PLL source to HSE oscillator:
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a- Switch the system clock source to HSI to allow modification of the PLL configuration
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b- Enable HSE Oscillator, select it as PLL source and finally activate the PLL
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c- Activate the Over Drive feature to reach 180 MHz as system clock frequency
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d- Select the PLL as system clock source and configure the HCLK, PCLK1 and PCLK2 clocks dividers
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e- Disable the HSI oscillator (optional, if the HSI is no more needed by the application)
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In this example the SYSCLK divided by 2 is outputted on the MCO2 pin(PC9).
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@note The selected clock to output onto MCO must not exceed 100 MHz (the maximum I/O speed).
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@note The SysTick 1 msec interrupt is required for the HAL process (Timeout management); by default
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the configuration is done using the HAL_Init() API, and when the system clock configuration
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is updated the SysTick configuration will be adjusted by the HAL_RCC_ClockConfig() API.
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Two LEDs are toggled with a timing defined by the HAL_Delay() API.
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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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RCC, System, Clock Configuration, HSE bypass mode, HSI, System clock, Oscillator, PLL
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@par Directory contents
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- RCC/RCC_ClockConfig/Inc/stm32f4xx_hal_conf.h HAL configuration file
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- RCC/RCC_ClockConfig/Inc/stm32f4xx_it.h Interrupt handlers header file
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- RCC/RCC_ClockConfig/Inc/main.h Main program header file
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- RCC/RCC_ClockConfig/Src/stm32f4xx_it.c Interrupt handlers
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- RCC/RCC_ClockConfig/Src/main.c Main program
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- RCC/RCC_ClockConfig/Src/system_stm32f4xx.c STM32F4xx system clock configuration file
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@par Hardware and Software environment
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- This example runs on STM32F429xx devices.
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- This example has been tested with STMicroelectronics STM32F429I-Discovery RevC
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boards and can be easily tailored to any other supported device
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and development board.
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- STM32F429I-Discovery RevC Set-up
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- Use LED3, LED4 connected respectively to PG.13 and PG.14 pins.
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- Use Key push button connected to PC.13 pin.
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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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