STM32CubeF0

@verbatim
******************** (C) COPYRIGHT 2016 STMicroelectronics *******************
* @file CRC/CRC_UserDefinedPolynomial/readme.txt
* @author MCD Application Team
* @brief Description of Cyclic Redundancy Check Example.
******************************************************************************
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@par Example Description

How to configure the CRC using the HAL API. The CRC (cyclic
redundancy check) calculation unit computes the 8-bit CRC code for a given
buffer of 32-bit data words, based on a user-defined generating polynomial.
In this example, the polynomial is set manually to 0x9B, that is,
X^8 + X^7 + X^4 + X^3 + X + 1.

At the beginning of the main program the HAL_Init() function is called to reset
all the peripherals, initialize the Flash interface and the systick.
Then the SystemClock_Config() function is used to configure the system
clock (SYSCLK).

The CRC peripheral configuration is ensured by the HAL_CRC_Init() function.
This later is calling the HAL_CRC_MspInit()function which core is implementing
the configuration of the needed CRC resources according to the used hardware (CLOCK,
GPIO, DMA and NVIC). You may update this function to change CRC configuration.

The calculated CRC code is saved in uwCRCValue variable.
Once calculated, the CRC value (uwCRCValue) is compared to the CRC expected value (uwExpectedCRCValue).

STM32 Nucleo board's LED can be used to monitor the example status:
- LED2 is ON when the correct CRC value is calculated
- LED2 is slowly blinking (1 sec. period) when there is an error in initialization or if an incorrect CRC value is calculated.

@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 need to ensure that the SysTick time base is always set to 1 millisecond
to have correct HAL operation.

@par Directory contents

- CRC/CRC_UserDefinedPolynomial/Inc/stm32f0xx_hal_conf.h HAL configuration file
- CRC/CRC_UserDefinedPolynomial/Inc/stm32f0xx_it.h Interrupt handlers header file
- CRC/CRC_UserDefinedPolynomial/Inc/main.h Header for main.c module
- CRC/CRC_UserDefinedPolynomial/Src/stm32f0xx_it.c Interrupt handlers
- CRC/CRC_UserDefinedPolynomial/Src/main.c Main program
- CRC/CRC_UserDefinedPolynomial/Src/stm32f0xx_hal_msp.c HAL MSP module
- CRC/CRC_UserDefinedPolynomial/Src/system_stm32f0xx.c STM32F0xx system source file

@par Hardware and Software environment

- This example runs on STM32F072RB devices.
- This example has been tested with STM32F072RB-Nucleo 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 example