123 lines
5.8 KiB
Plaintext
123 lines
5.8 KiB
Plaintext
/**
|
||
@page RCC_ClockConfig RCC Clock Configuration example
|
||
|
||
@verbatim
|
||
******************** (C) COPYRIGHT 2017 STMicroelectronics *******************
|
||
* @file RCC/RCC_ClockConfig/readme.txt
|
||
* @author MCD Application Team
|
||
* @brief Description of the RCC Clock Configuration example.
|
||
******************************************************************************
|
||
* @attention
|
||
*
|
||
* Copyright (c) 2017 STMicroelectronics.
|
||
* All rights reserved.
|
||
*
|
||
* This software is licensed under terms that can be found in the LICENSE file
|
||
* in the root directory of this software component.
|
||
* If no LICENSE file comes with this software, it is provided AS-IS.
|
||
*
|
||
******************************************************************************
|
||
@endverbatim
|
||
|
||
@par Example Description
|
||
|
||
This example describes how to use the RCC HAL API to configure the system clock (SYSCLK)
|
||
and modify the clock settings in Run mode.
|
||
|
||
In this example, after startup SYSCLK is configured to the max frequency using the PLL with
|
||
HSI as clock source, the STM32F411RE-Nucleo board Key button (connected to EXTI Line13) will be
|
||
used to change the PLL source: from HSI to HSE, and vice versa.
|
||
Each time the Key button is pressed; EXTI Line13 interrupt is generated and the
|
||
PLL oscillator source is checked using __HAL_RCC_GET_PLL_OSCSOURCE() macro:
|
||
|
||
1- If the HSI oscillator is selected as PLL source, the following steps will be followed to switch
|
||
the PLL source to HSE oscillator:
|
||
a- Switch the system clock source to HSI to allow modification of the PLL configuration
|
||
b- Depending on the uncommented define in the main.h file, one of the two following
|
||
possibilities is applied:
|
||
- if defined "HSE_CRYSTAL": the HSE Oscillator is then selected as the input
|
||
PLL source and consequently we need to Enable it before selecting it as PLL
|
||
source and finally activate the PLL
|
||
- if defined "HSE_BYPASS": then the input clock will come from the MCO from
|
||
ST_LINK MCU-STM32F103. This frequency cannot be changed, and it is fixed
|
||
at 8 MHz, connected to PF1/PH0-OSC_IN of STM32F4xx device.
|
||
This will require to enable the HSE Bypass before selecting it as PLL
|
||
source and finally activate the PLL
|
||
c- Select the PLL as system clock source and configure the HCLK, PCLK1 and PCLK2 clocks dividers
|
||
d- Disable the HSI oscillator (optional, if the HSI is no more needed by the application)
|
||
|
||
2- If the HSE oscillator is selected as PLL source, the following steps will be followed to switch
|
||
the PLL source to HSI oscillator:
|
||
a- Switch the system clock source to HSE to allow modification of the PLL configuration
|
||
b- Enable HSI Oscillator, select it as PLL source and finally activate the PLL
|
||
c- Select the PLL as system clock source and configure the HCLK, PCLK1 and PCLK2 clocks dividers
|
||
d- Disable the HSE oscillator (optional, if the HSE is no more needed by the application)
|
||
|
||
In this example the SYSCLK divided by 2 is outputted on the MCO2 pin(PC9).
|
||
|
||
@note The selected clock to output onto MCO must not exceed 100 MHz (the maximum I/O speed).
|
||
@note The SysTick 1 msec interrupt is required for the HAL process (Timeout management);
|
||
by default the configuration is done using the HAL_Init() API, and when the
|
||
system clock configuration is updated the SysTick configuration will be
|
||
adjusted by the HAL_RCC_ClockConfig() API.
|
||
|
||
One LED is toggled with a timing defined by the HAL_Delay() API.
|
||
|
||
|
||
@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)
|
||
than the peripheral interrupt. Otherwise the caller ISR process will be blocked.
|
||
To change the SysTick interrupt priority you have to use HAL_NVIC_SetPriority() function.
|
||
|
||
@note The application needs to ensure that the SysTick time base is always set to
|
||
1 millisecond to have correct HAL operation.
|
||
|
||
@note The clock setting is configured to have the max product performance (max clock frequency)
|
||
so not optimized in term of power consumption.
|
||
|
||
@par Keywords
|
||
|
||
RCC, System, Clock Configuration, HSE bypass mode, HSI, System clock, Oscillator, PLL
|
||
|
||
@par Directory contents
|
||
|
||
- RCC/RCC_ClockConfig/Inc/stm32f4xx_hal_conf.h HAL configuration file
|
||
- RCC/RCC_ClockConfig/Inc/stm32f4xx_it.h Interrupt handlers header file
|
||
- RCC/RCC_ClockConfig/Inc/main.h Main program header file
|
||
- RCC/RCC_ClockConfig/Src/stm32f4xx_it.c Interrupt handlers
|
||
- RCC/RCC_ClockConfig/Src/main.c Main program
|
||
- RCC/RCC_ClockConfig/Src/system_stm32f4xx.c STM32F4xx system clock configuration file
|
||
|
||
|
||
@par Hardware and Software environment
|
||
|
||
- This example runs on STM32F411xEx devices.
|
||
|
||
- This example has been tested with STMicroelectronics STM32F4xx-Nucleo RevC
|
||
boards and can be easily tailored to any other supported device
|
||
and development board.
|
||
|
||
- STM32F4xx-Nucleo RevC Set-up
|
||
- Use LED2 connected to PA.05 pins.
|
||
- Use Key push button connected to PC.13 pin.
|
||
- HSE crystal (8MHZ) need to be mounted on Nucleo board if the HSE_CRYSTAL is
|
||
uncommented on in the main.h file
|
||
Otherwise, if HSE_BYPASS is selected, the following configuration on the board
|
||
need to be applied:
|
||
– Solder bridges SB54 and SB55 have to be OFF
|
||
– Resistor R35 has to be removed
|
||
– Solder bridges SB16 and SB50 have to be ON.
|
||
|
||
|
||
@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
|
||
|
||
|
||
*/
|