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 /**
   ******************************************************************************
   * @file    stm32f1xx_hal_crc.c
   * @author  MCD Application Team
   * @brief   CRC HAL module driver.
   *          This file provides firmware functions to manage the following
   *          functionalities of the Cyclic Redundancy Check (CRC) peripheral:
   *           + Initialization and de-initialization functions
   *           + Peripheral Control functions
   *           + Peripheral State functions
+  *
   @verbatim
-  ==============================================================================
+ ===============================================================================
                      ##### How to use this driver #####
-  ==============================================================================
+ ===============================================================================
     [..]
+         (+) Enable CRC AHB clock using __HAL_RCC_CRC_CLK_ENABLE();
+         (+) Initialize CRC calculator
+             (++) specify generating polynomial (peripheral default or non-default one)
+             (++) specify initialization value (peripheral default or non-default one)
-      The CRC HAL driver can be used as follows:
+             (++) specify input data format
-      (#) Enable CRC AHB clock using __HAL_RCC_CRC_CLK_ENABLE();
+             (++) specify input or output data inversion mode if any
-      (#) Use HAL_CRC_Accumulate() function to compute the CRC value of
+         (+) Use HAL_CRC_Accumulate() function to compute the CRC value of the
-          a 32-bit data buffer using combination of the previous CRC value
+             input data buffer starting with the previously computed CRC as
-          and the new one.
+             initialization value
-      (#) Use HAL_CRC_Calculate() function to compute the CRC Value of
+         (+) Use HAL_CRC_Calculate() function to compute the CRC value of the
-          a new 32-bit data buffer. This function resets the CRC computation
+             input data buffer starting with the defined initialization value
-          unit before starting the computation to avoid getting wrong CRC values.
+             (default or non-default) to initiate CRC calculation
   @endverbatim
   ******************************************************************************
   * @attention
+  *
-  * <h2><center>&copy; COPYRIGHT(c) 2016 STMicroelectronics</center></h2>
+  * <h2><center>&copy; Copyright (c) 2016 STMicroelectronics.
-  *
-  * 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.
+  * All rights reserved.</center></h2>
+  *
-  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+  * This software component is licensed by ST under BSD 3-Clause license,
-  * 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
+  * the "License"; You may not use this file except in compliance with the
-  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+  * License. You may obtain a copy of the License at:
-  * 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.
+  *                        opensource.org/licenses/BSD-3-Clause
+  *
   ******************************************************************************
   */
 /* Includes ------------------------------------------------------------------*/
 /* Private typedef -----------------------------------------------------------*/
 /* Private define ------------------------------------------------------------*/
 /* Private macro -------------------------------------------------------------*/
 /* Private variables ---------------------------------------------------------*/
 /* Private function prototypes -----------------------------------------------*/
-/* Private functions ---------------------------------------------------------*/
+/* Exported functions --------------------------------------------------------*/
 /** @defgroup CRC_Exported_Functions CRC Exported Functions
   * @{
   */
 /** @defgroup CRC_Exported_Functions_Group1 Initialization and de-initialization functions
  *  @brief    Initialization and Configuration functions.
+ *
 @verbatim
-  ==============================================================================
+ ===============================================================================
             ##### Initialization and de-initialization functions #####
-  ==============================================================================
+ ===============================================================================
     [..]  This section provides functions allowing to:
       (+) Initialize the CRC according to the specified parameters
           in the CRC_InitTypeDef and create the associated handle
       (+) DeInitialize the CRC peripheral
-      (+) Initialize the CRC MSP
+      (+) Initialize the CRC MSP (MCU Specific Package)
-      (+) DeInitialize CRC MSP
+      (+) DeInitialize the CRC MSP
 @endverbatim
   * @{
   */
 /**
-  * @brief  Initializes the CRC according to the specified
+  * @brief  Initialize the CRC according to the specified
-  *         parameters in the CRC_InitTypeDef and creates the associated handle.
+  *         parameters in the CRC_InitTypeDef and create the associated handle.
-  * @param  hcrc: pointer to a CRC_HandleTypeDef structure that contains
+  * @param  hcrc CRC handle
-  *         the configuration information for CRC
   * @retval HAL status
   */
 HAL_StatusTypeDef HAL_CRC_Init(CRC_HandleTypeDef *hcrc)
+{
   /* Check the CRC handle allocation */
-  if(hcrc == NULL)
+  if (hcrc == NULL)
+  {
     return HAL_ERROR;
+  }
   /* Check the parameters */
   assert_param(IS_CRC_ALL_INSTANCE(hcrc->Instance));
-  if(hcrc->State == HAL_CRC_STATE_RESET)
+  if (hcrc->State == HAL_CRC_STATE_RESET)
+  {
     /* Allocate lock resource and initialize it */
     hcrc->Lock = HAL_UNLOCKED;
     /* Init the low level hardware */
     HAL_CRC_MspInit(hcrc);
+  }
   /* Change CRC peripheral state */
   hcrc->State = HAL_CRC_STATE_READY;
   /* Return function status */
   return HAL_OK;
+}
 /**
-  * @brief  DeInitializes the CRC peripheral.
+  * @brief  DeInitialize the CRC peripheral.
-  * @param  hcrc: pointer to a CRC_HandleTypeDef structure that contains
+  * @param  hcrc CRC handle
-  *         the configuration information for CRC
   * @retval HAL status
   */
 HAL_StatusTypeDef HAL_CRC_DeInit(CRC_HandleTypeDef *hcrc)
+{
   /* Check the CRC handle allocation */
-  if(hcrc == NULL)
+  if (hcrc == NULL)
+  {
     return HAL_ERROR;
+  }
   /* Check the parameters */
   assert_param(IS_CRC_ALL_INSTANCE(hcrc->Instance));
+  /* Check the CRC peripheral state */
+  if (hcrc->State == HAL_CRC_STATE_BUSY)
+  {
+    return HAL_BUSY;
+  }
   /* Change CRC peripheral state */
   hcrc->State = HAL_CRC_STATE_BUSY;
-  /* DeInit the low level hardware */
+  /* Reset CRC calculation unit */
-  HAL_CRC_MspDeInit(hcrc);
-  /* Resets the CRC calculation unit and sets the data register to 0xFFFF FFFF */
   __HAL_CRC_DR_RESET(hcrc);
   /* Reset IDR register content */
   CLEAR_BIT(hcrc->Instance->IDR, CRC_IDR_IDR);
+  /* DeInit the low level hardware */
+  HAL_CRC_MspDeInit(hcrc);
   /* Change CRC peripheral state */
   hcrc->State = HAL_CRC_STATE_RESET;
-  /* Release Lock */
+  /* Process unlocked */
   __HAL_UNLOCK(hcrc);
   /* Return function status */
   return HAL_OK;
+}
 /**
   * @brief  Initializes the CRC MSP.
-  * @param  hcrc: pointer to a CRC_HandleTypeDef structure that contains
+  * @param  hcrc CRC handle
-  *         the configuration information for CRC
   * @retval None
   */
 __weak void HAL_CRC_MspInit(CRC_HandleTypeDef *hcrc)
+{
   /* Prevent unused argument(s) compilation warning */
   UNUSED(hcrc);
-  /* NOTE : This function Should not be modified, when the callback is needed,
+  /* NOTE : This function should not be modified, when the callback is needed,
-            the HAL_CRC_MspInit could be implemented in the user file
+            the HAL_CRC_MspInit can be implemented in the user file
    */
+}
 /**
-  * @brief  DeInitializes the CRC MSP.
+  * @brief  DeInitialize the CRC MSP.
-  * @param  hcrc: pointer to a CRC_HandleTypeDef structure that contains
+  * @param  hcrc CRC handle
-  *         the configuration information for CRC
   * @retval None
   */
 __weak void HAL_CRC_MspDeInit(CRC_HandleTypeDef *hcrc)
+{
   /* Prevent unused argument(s) compilation warning */
   UNUSED(hcrc);
-  /* NOTE : This function Should not be modified, when the callback is needed,
+  /* NOTE : This function should not be modified, when the callback is needed,
-            the HAL_CRC_MspDeInit could be implemented in the user file
+            the HAL_CRC_MspDeInit can be implemented in the user file
    */
+}
 /**
   * @}
   */
 /** @defgroup CRC_Exported_Functions_Group2 Peripheral Control functions
  *  @brief    management functions.
+ *
 @verbatim
-  ==============================================================================
+ ===============================================================================
                       ##### Peripheral Control functions #####
-  ==============================================================================
+ ===============================================================================
     [..]  This section provides functions allowing to:
-      (+) Compute the 32-bit CRC value of 32-bit data buffer,
+      (+) compute the 32-bit CRC value of a 32-bit data buffer
           using combination of the previous CRC value and the new one.
+       [..]  or
-      (+) Compute the 32-bit CRC value of 32-bit data buffer,
+      (+) compute the 32-bit CRC value of a 32-bit data buffer
           independently of the previous CRC value.
 @endverbatim
   * @{
   */
 /**
-  * @brief  Computes the 32-bit CRC of 32-bit data buffer using combination
+  * @brief  Compute the 32-bit CRC value of a 32-bit data buffer
-  *         of the previous CRC value and the new one.
+  *         starting with the previously computed CRC as initialization value.
-  * @param  hcrc: pointer to a CRC_HandleTypeDef structure that contains
+  * @param  hcrc CRC handle
-  *         the configuration information for CRC
+  * @param  pBuffer pointer to the input data buffer.
-  * @param  pBuffer: pointer to the buffer containing the data to be computed
+  * @param  BufferLength input data buffer length (number of uint32_t words).
-  * @param  BufferLength: length of the buffer to be computed (defined in word, 4 bytes)
+  * @retval uint32_t CRC (returned value LSBs for CRC shorter than 32 bits)
-  * @retval 32-bit CRC
   */
 uint32_t HAL_CRC_Accumulate(CRC_HandleTypeDef *hcrc, uint32_t pBuffer[], uint32_t BufferLength)
+{
-  uint32_t index = 0U;
+  uint32_t index;      /* CRC input data buffer index */
-  /* Process Locked */
+  uint32_t temp = 0U;  /* CRC output (read from hcrc->Instance->DR register) */
-  __HAL_LOCK(hcrc);
   /* Change CRC peripheral state */
   hcrc->State = HAL_CRC_STATE_BUSY;
   /* Enter Data to the CRC calculator */
-  for(index = 0U; index < BufferLength; index++)
+  for (index = 0U; index < BufferLength; index++)
+  {
     hcrc->Instance->DR = pBuffer[index];
+  }
+  temp = hcrc->Instance->DR;
   /* Change CRC peripheral state */
   hcrc->State = HAL_CRC_STATE_READY;
-  /* Process Unlocked */
-  __HAL_UNLOCK(hcrc);
   /* Return the CRC computed value */
-  return hcrc->Instance->DR;
+  return temp;
+}
 /**
-  * @brief  Computes the 32-bit CRC of 32-bit data buffer independently
+  * @brief  Compute the 32-bit CRC value of a 32-bit data buffer
-  *         of the previous CRC value.
+  *         starting with hcrc->Instance->INIT as initialization value.
-  * @param  hcrc: pointer to a CRC_HandleTypeDef structure that contains
+  * @param  hcrc CRC handle
-  *         the configuration information for CRC
+  * @param  pBuffer pointer to the input data buffer.
-  * @param  pBuffer: Pointer to the buffer containing the data to be computed
+  * @param  BufferLength input data buffer length (number of uint32_t words).
-  * @param  BufferLength: Length of the buffer to be computed (defined in word, 4 bytes)
+  * @retval uint32_t CRC (returned value LSBs for CRC shorter than 32 bits)
-  * @retval 32-bit CRC
   */
 uint32_t HAL_CRC_Calculate(CRC_HandleTypeDef *hcrc, uint32_t pBuffer[], uint32_t BufferLength)
+{
-  uint32_t index = 0U;
+  uint32_t index;      /* CRC input data buffer index */
-  /* Process Locked */
+  uint32_t temp = 0U;  /* CRC output (read from hcrc->Instance->DR register) */
-  __HAL_LOCK(hcrc);
   /* Change CRC peripheral state */
   hcrc->State = HAL_CRC_STATE_BUSY;
-  /* Reset CRC Calculation Unit */
+  /* Reset CRC Calculation Unit (hcrc->Instance->INIT is
+  *  written in hcrc->Instance->DR) */
   __HAL_CRC_DR_RESET(hcrc);
-  /* Enter Data to the CRC calculator */
+  /* Enter 32-bit input data to the CRC calculator */
-  for(index = 0U; index < BufferLength; index++)
+  for (index = 0U; index < BufferLength; index++)
+  {
     hcrc->Instance->DR = pBuffer[index];
+  }
+  temp = hcrc->Instance->DR;
   /* Change CRC peripheral state */
   hcrc->State = HAL_CRC_STATE_READY;
-  /* Process Unlocked */
-  __HAL_UNLOCK(hcrc);
   /* Return the CRC computed value */
-  return hcrc->Instance->DR;
+  return temp;
+}
 /**
   * @}
   */
 /** @defgroup CRC_Exported_Functions_Group3 Peripheral State functions
  *  @brief    Peripheral State functions.
+ *
 @verbatim
-  ==============================================================================
+ ===============================================================================
                       ##### Peripheral State functions #####
-  ==============================================================================
+ ===============================================================================
     [..]
     This subsection permits to get in run-time the status of the peripheral.
 @endverbatim
   * @{
   */
 /**
-  * @brief  Returns the CRC state.
+  * @brief  Return the CRC handle state.
-  * @param  hcrc: pointer to a CRC_HandleTypeDef structure that contains
+  * @param  hcrc CRC handle
-  *         the configuration information for CRC
   * @retval HAL state
   */
 HAL_CRC_StateTypeDef HAL_CRC_GetState(CRC_HandleTypeDef *hcrc)
+{
+  /* Return CRC handle state */
   return hcrc->State;
+}
 /**
   * @}
 /**
   * @}
   */
 #endif /* HAL_CRC_MODULE_ENABLED */
 /**
   * @}
   */

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