STM32CubeF3

@verbatim
******************** (C) COPYRIGHT 2016 STMicroelectronics *******************
* @file CRC/CRC_Bytes_Stream_7bit_CRC/readme.txt
* @author MCD Application Team
* @brief 7-bit long CRC computation from bytes (8-bit data) buffers.
******************************************************************************
*
* Redistribution and use in source and binary forms, with or without modification,
* are permitted provided that the following conditions are met:
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
* 3. Neither the name of STMicroelectronics nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
******************************************************************************
@endverbatim

@par Example Description

This example guides you through the different configuration steps by means of the
HAL API. The CRC (Cyclic Redundancy Check) calculation unit computes 7-bit long
CRC codes derived from buffers of 8-bit data (bytes).
The user-defined generating polynomial is manually set to 0x65 that is
X^7 + X^6 + X^5 + X^2 + 1, used in Train Communication Network, IEC 60870-5[17].

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 HAL_CRC_Init() function.
The latter is calling HAL_CRC_MspInit() function which core is implementing
the configuration of the needed CRC resources according to the used hardware (CLOCK).
You can update HAL_CRC_Init() input parameters to change the CRC configuration.

In this example, the user-defined generating polynomial is configured by
HAL_CRC_Init(). At the same time, it is set that neither input or output data
must be reversed, the default init value is used and it is specified that input
data type is byte.

First, a 5-byte long buffer is processed to yield a first CRC.

Next, a second CRC is computed from a 17-byte long buffer. For the latter,
the CRC calculator is not re-initialized and instead the previously computed CRC
is used as initial value.

Then, a third CRC is computed from a 1-byte long buffer. Again, the CRC calculator
is not re-initialized, the previously computed CRC is used as initial value.

Finally, a fourth CRC is computed from a 2-byte long buffer. This time, the CRC
calculator is re-initialized with the IP default value that is 0x7F for a 7-bit CRC.
This is done with a call to HAL_CRC_Calculate() instead of HAL_CRC_Accumulate().

Each time, the calculated CRC code is stored in uwCRCValue variable.
Once calculated, the CRC value (uwCRCValue) is compared to the CRC expected value (uwExpectedCRCValue_1, 2, 3 or 4).

STM32 board LED is 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 needs to ensure that the SysTick time base is always set to 1 millisecond
to have correct HAL operation.

@par Directory contents

- CRC/CRC_Bytes_Stream_7bit_CRC/Inc/stm32f3xx_hal_conf.h HAL configuration file
- CRC/CRC_Bytes_Stream_7bit_CRC/Inc/stm32f3xx_it.h Interrupt handlers header file
- CRC/CRC_Bytes_Stream_7bit_CRC/Inc/main.h Header for main.c module
- CRC/CRC_Bytes_Stream_7bit_CRC/Src/stm32f3xx_it.c Interrupt handlers
- CRC/CRC_Bytes_Stream_7bit_CRC/Src/main.c Main program
- CRC/CRC_Bytes_Stream_7bit_CRC/Src/stm32f3xx_hal_msp.c HAL MSP module
- CRC/CRC_Bytes_Stream_7bit_CRC/Src/system_stm32f3xx.c STM32F3xx system source file

@par Hardware and Software environment

- This example runs on STM32F334R8 devices.
- This example has been tested with STM32F334R8-Nucleo Rev C 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