95 lines
4.5 KiB
Plaintext
95 lines
4.5 KiB
Plaintext
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/**
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@page RCC_ClockConfig RCC Clock Config 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 Config example.
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******************************************************************************
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* @attention
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*
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* <h2><center>© Copyright (c) 2017 STMicroelectronics.
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* All rights reserved.</center></h2>
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*
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* This software component is licensed by ST under BSD 3-Clause license,
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* the "License"; You may not use this file except in compliance with the
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* License. You may obtain a copy of the License at:
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* opensource.org/licenses/BSD-3-Clause
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*
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******************************************************************************
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@endverbatim
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@par Example Description
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Configuration of the system clock (SYSCLK) and modification of the clock settings in Run mode, using the RCC HAL API.
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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 EVAL board Key button (connected to EXTI Line15) 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 Line15 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- Select the PLL as system clock source and configure the HCLK, PCLK1 and PCLK2 clocks dividers
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d- 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- Select the PLL as system clock source and configure the HCLK, PCLK1 and PCLK2 clocks dividers
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d- 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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Three 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 Directory contents
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- RCC/RCC_ClockConfig/Inc/stm32f2xx_hal_conf.h HAL configuration file
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- RCC/RCC_ClockConfig/Inc/stm32f2xx_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/stm32f2xx_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_stm32f2xx.c STM32F2xx system clock configuration file
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@par Hardware and Software environment
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- This example runs on STM32F207xx/217xx device.
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- This example has been tested with STMicroelectronics STM322xG-EVAL
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evaluation boards and can be easily tailored to any other supported device
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and development board.
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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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* <h3><center>© COPYRIGHT STMicroelectronics</center></h3>
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*/
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