STM32CubeF4

@verbatim
******************** (C) COPYRIGHT 2017 STMicroelectronics *******************
* @file FreeRTOS/FreeRTOS_Semaphore/readme.txt
* @author MCD Application Team
* @brief Description of the FreeRTOS Semaphore application.
******************************************************************************
*
* Copyright (c) 2017 STMicroelectronics. All rights reserved.
*
* This software component is licensed by ST under Ultimate Liberty license
* SLA0044, the "License"; You may not use this file except in compliance with
* the License. You may obtain a copy of the License at:
* www.st.com/SLA0044
*
******************************************************************************
@endverbatim

@par Application Description

How to use semaphores with CMSIS RTOS API.

This application creates two threads that toggle LEDs through a shared semaphore.

The first thread, having the higher priority, obtains the semaphore and
toggles the LED1 each 200 ms. After 5 seconds it releases the semaphore and
suspends itself. The low priority thread can execute now, it obtains the
semaphore and resumes execution of the first thread. As it has the higher
priority, the first thread will try to obtain the semaphore but it fails
because the semaphore is already taken by the low
priority thread. The latter will toggle the LED3 for 5 seconds before releasing
the semaphore and begin a new cycle

@note Care must be taken when using HAL_Delay(), this function provides accurate delay (in milliseconds)
based on variable incremented in HAL time base ISR. This implies that if HAL_Delay() is called from
a peripheral ISR process, then the HAL time base interrupt must have higher priority (numerically lower)
than the peripheral interrupt. Otherwise the caller ISR process will be blocked.
To change the HAL time base interrupt priority you have to use HAL_NVIC_SetPriority() function.

@note The application needs to ensure that the HAL time base is always set to 1 millisecond to have correct
HAL operation.

@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.

For more details about FreeRTOS implementation on STM32Cube, please refer to UM1722 "Developing Applications
on STM32Cube with RTOS".

@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.
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.

@par Keywords

RTOS, FreeRTOS, Thread, Semaphore, Priorities

@par Directory contents

- FreeRTOS/FreeRTOS_Semaphore/Inc/main.h Main program header file
- FreeRTOS/FreeRTOS_Semaphore/Inc/stm32f4xx_hal_conf.h HAL Library Configuration file
- FreeRTOS/FreeRTOS_Semaphore/Inc/stm32f4xx_it.h Interrupt handlers header file
- FreeRTOS/FreeRTOS_Semaphore/Inc/FreeRTOSConfig.h FreeRTOS Configuration file
- FreeRTOS/FreeRTOS_Semaphore/Src/main.c Main program
- FreeRTOS/FreeRTOS_Semaphore/Src/stm32f4xx_it.c Interrupt handlers
- FreeRTOS/FreeRTOS_Semaphore/Src/system_stm32f4xx.c STM32F4xx system clock configuration file

@par Hardware and Software environment

- This application runs on STM32F469xx and STM32F479xx devices.

- This application has been tested with STM32469I-EVAL RevC board and can be
easily tailored to any other supported device and development board.

@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 application