99 lines
4.4 KiB
Plaintext
99 lines
4.4 KiB
Plaintext
/**
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@page RTC_LSI RTC prescaler adjustment with LSI Measurements example
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@verbatim
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******************** (C) COPYRIGHT 2016 STMicroelectronics *******************
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* @file RTC/RTC_LSI/readme.txt
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* @author MCD Application Team
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* @brief Description of the RTC prescaler adjustment with LSI Measurements example.
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******************************************************************************
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* @attention
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*
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* <h2><center>© Copyright (c) 2016 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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Use of the LSI clock source autocalibration to get a precise RTC clock.
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In the associated software, the system clock is set to 72 MHz.
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As an application example, it demonstrates how to configure the TIM5 timer
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internally connected to LSI clock output, in order to adjust the RTC prescaler.
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The Low Speed Internal (LSI) clock is used as RTC clock source.
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After reset, the RTC prescaler is set with the default LSI frequency (40 kHz).
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The RTC WakeUp is configured to generate an interrupt each 1s.
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A key value is written in backup data register 1 to indicate if the wakeup timer has
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already been enabled. If so the wakeup timer is disabled prior configuring the RTC
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automatic wakeup.
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LED1 is toggled inside the RTC WakeUp interrupt each 1s.
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The inaccuracy of the LSI clock causes the RTC WakeUp Interrupt to be inaccurate.
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The RTC CK_SPRE signal can be monitored by LED1 which is toggled into the RTC
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Wakeup interrupt service routine.
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The program waits until Key push-button is pressed to begin the auto calibration
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procedure:
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- Configure the TIM5 to remap internally the TIM5 TIM_CHANNEL_4
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Input Capture to the LSI clock output.
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- Enable the TIM5 Input Capture interrupt: after one cycle of LSI clock, the
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period value is stored in a variable and compared to the HCLK clock to get
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its real value.
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- The RTC prescaler is adjusted with this LSI frequency value so that the RTC
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CK_SPRE value become more accurate.
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- When calibration is done the variable uwLsiFreq is visualized into the debugger
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to indicate the end of this operation.
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- The LSI value is updated and displayed on the debugger in uwLsiFreq variable.
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- LED3 is On: This indicates that the system generates an error.
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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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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 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 Directory contents
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- RTC/RTC_LSI/Inc/stm32f1xx_conf.h Library Configuration file
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- RTC/RTC_LSI/Inc/main.h header file for main.c
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- RTC/RTC_LSI/Inc/stm32f1xx_it.h Header for stm32f1xx_it.c
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- RTC/RTC_LSI/Src/system_stm32f1xx.c STM32F1xx system clock configuration file
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- RTC/RTC_LSI/Src/stm32f1xx_it.c Interrupt handlers
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- RTC/RTC_LSI/Src/main.c Main program
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- RTC/RTC_LSI/Src/stm32f1xx_hal_msp.c HAL MSP module
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@par Hardware and Software environment
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- This example runs on STM32F107xC devices.
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- This example has been tested with STM3210C-EVAL RevC board and can be
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easily tailored to any other supported device and development board.
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- STM3210C-EVAL RevC Set-up
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- Use LED1 connected to PD.07 pin (pin 15 in CN8 connector).
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- Use the Key push-button connected to pin PB.09 (EXTI_Line9-5)
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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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