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102 lines
4.5 KiB
Plaintext
102 lines
4.5 KiB
Plaintext
/**
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@page FreeRTOS_LowPower FreeRTOS Low Power example
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@verbatim
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******************** (C) COPYRIGHT 2017 STMicroelectronics *******************
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* @file FreeRTOS/FreeRTOS_LowPower/readme.txt
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* @author MCD Application Team
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* @brief Description of the FreeRTOS Low Power example.
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******************************************************************************
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*
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* Copyright (c) 2017 STMicroelectronics. All rights reserved.
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*
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* This software component is licensed by ST under Ultimate Liberty license
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* SLA0044, the "License"; You may not use this file except in compliance with
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* the License. You may obtain a copy of the License at:
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* www.st.com/SLA0044
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*
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******************************************************************************
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@endverbatim
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@par Application Description
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How to enter and exit low-power mode with CMSIS RTOS API.
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This application creates two threads.
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+ An Rx thread that blocks on a queue to wait for data, blinking LED each
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time data is received (turning it on and then off again) before returning
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to block on the queue once more.
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+ A Tx thread that repeatedly enters the Blocked state for 500ms.
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On exiting the blocked state, the Tx thread sends a value through the queue
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to the Rx thread (causing the Rx thread to exit the blocked state and blink
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the LED).
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Blocking for a finite period allows the kernel to stop the tick interrupt
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and place the STM32 into sleep mode - the lowest power mode possible
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that allows the CPU registers and RAM to retain their state.
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In this application, not used GPIOs are configured to analog. This helps reduce
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the power consumption of the device.
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Observed behaviour:
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Every 500ms the MCU will come out of the low power state to turn the LED1 on,
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then return to the low power state for 20ms before leaving the low power
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state again to turn the LED1 off. This will be observed as a fast blinking
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on the LED1.
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The RTOS tick is suppressed while the MCU is in its low power state.
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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 HAL time base ISR. This implies that if HAL_Delay() is called from
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a peripheral ISR process, then the HAL time base 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 HAL time base interrupt priority you have to use HAL_NVIC_SetPriority() function.
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@note The application needs to ensure that the HAL time base is always set to 1 millisecond to have correct
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HAL operation.
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@note The FreeRTOS heap size configTOTAL_HEAP_SIZE defined in FreeRTOSConfig.h is set according to the OS resources memory requirements of the application with +10% margin and rounded to the upper Kbyte boundary.
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For more details about FreeRTOS implementation on STM32Cube, please refer to UM1722 "Developing Applications
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on STM32Cube with RTOS".
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@note The connection of the LCD reset pin to a dedicated GPIO PK7 instead of the STM32F469 NRST pin may cause residual display on LCD with applications/examples that do not require display.
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The LCD clear can be ensured by hardware through the board's power off/power on or by software calling the BSP_LCD_Reset() function.
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@par Keywords
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RTOS, FreeRTOS, Low power, MPU
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@par Directory contents
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- FreeRTOS/FreeRTOS_LowPower/Inc/main.h Main program header file
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- FreeRTOS/FreeRTOS_LowPower/Inc/stm32f4xx_hal_conf.h HAL Library Configuration file
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- FreeRTOS/FreeRTOS_LowPower/Inc/stm32f4xx_it.h Interrupt handlers header file
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- FreeRTOS/FreeRTOS_LowPower/Inc/FreeRTOSConfig.h FreeRTOS Configuration file
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- FreeRTOS/FreeRTOS_LowPower/Src/main.c Main program
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- FreeRTOS/FreeRTOS_LowPower/Src/stm32f4xx_it.c Interrupt handlers
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- FreeRTOS/FreeRTOS_LowPower/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 STM32F469xx and STM32F479xx devices.
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- This example has been tested with STM32469I-EVAL RevC board and can be
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easily tailored to any other supported device 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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