CRC校验的问题

chenbingjy

CRC校验的问题 [复制链接]

我找到一个STM32L4R5ZIT6的关于CRC的例程，

 

代码如下

#include "main.h"

/** @addtogroup STM32L4xx_HAL_Examples
  * @{
  */

/** @addtogroup CRC_Bytes_Stream_7bit_CRC
  * @{
  */

/* Private typedef -----------------------------------------------------------*/
/* Private define ------------------------------------------------------------*/
#define BUFFER_SIZE_5  5  /* CRC7_DATA8_TEST5[] is 5-byte long   */ 
#define BUFFER_SIZE_17 17 /* CRC7_DATA8_TEST17[] is 17-byte long */ 
#define BUFFER_SIZE_1  1  /* CRC7_DATA8_TEST1[] is 1-byte long   */ 
#define BUFFER_SIZE_2  2  /* CRC7_DATA8_TEST2[] is 2-byte long   */ 

/* User-defined polynomial */
#define CRC_POLYNOMIAL_7B  0x65  /* X^7 + X^6 + X^5 + X^2 + 1,
                                   used in Train Communication Network, IEC 60870-5[17] */

/* Private macro -------------------------------------------------------------*/
/* Private variables ---------------------------------------------------------*/
/* CRC handler declaration */
CRC_HandleTypeDef   CrcHandle;

/* Used for storing CRC Value */
__IO uint32_t uwCRCValue = 0;

/* Bytes buffers that will consecutively yield CRCs */
static const uint8_t CRC7_DATA8_TEST5[5]   = {0x12,0x34,0xBA,0x71,0xAD};
static const uint8_t CRC7_DATA8_TEST17[17] = {0x12,0x34,0xBA,0x71,0xAD,
                                              0x11,0x56,0xDC,0x88,0x1B,
                                              0xEE,0x4D,0x82, 0x93,0xA6,
                                              0x7F,0xC3};
static const uint8_t CRC7_DATA8_TEST1[1]   = {0x19};                                                
static const uint8_t CRC7_DATA8_TEST2[2]   = {0xAB,0xCD};

       

/* Expected CRC Values */
/* The 7 LSB bits are the 7-bit long CRC */
uint32_t uwExpectedCRCValue_1 = 0x00000057;    /* First byte stream CRC  */
uint32_t uwExpectedCRCValue_2 = 0x0000006E;    /* Second byte stream CRC */
uint32_t uwExpectedCRCValue_3 = 0x0000004B;    /* Third byte stream CRC  */
uint32_t uwExpectedCRCValue_4 = 0x00000026;    /* Fourth byte stream CRC */

/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void Error_Handler(void);

/* Private functions ---------------------------------------------------------*/

/**
  * [url=home.php?mod=space&uid=159083]@brief[/url] Main program
  * @param  None
  * @retval None
  */
int main(void)
{

  /* STM32L4xx HAL library initialization:
       - Configure the Flash prefetch
       - Systick timer is configured by default as source of time base, but user 
         can eventually implement his proper time base source (a general purpose 
         timer for example or other time source), keeping in mind that Time base 
         duration should be kept 1ms since PPP_TIMEOUT_VALUEs are defined and 
         handled in milliseconds basis.
       - Set NVIC Group Priority to 4
       - Low Level Initialization
     */
  HAL_Init();
  
  /* Configure the system clock to 120 MHz */
  SystemClock_Config();

  /* Configure LED1 and LED3 */
  BSP_LED_Init(LED1);
  BSP_LED_Init(LED3);


  /****************************************************************************/
  /*                                                                          */
  /*                     CRC peripheral initialization                        */
  /*                                                                          */    
  /****************************************************************************/
    
  CrcHandle.Instance = CRC;

  /* The default polynomial is not used. The one to be used must be defined 
     in CrcHandle.Init.GeneratingPolynomial */  
  CrcHandle.Init.DefaultPolynomialUse    = DEFAULT_POLYNOMIAL_DISABLE;
  
  /* Set the value of the generating polynomial. 
    The one used in that example is the 7-bit long CRC generating
    polynomial X^7 + X^6 + X^5 + X^2 + 1 */
  CrcHandle.Init.GeneratingPolynomial    = CRC_POLYNOMIAL_7B;
  
  /* The user-defined generating polynomial yields a 7-bit long CRC */
  CrcHandle.Init.CRCLength               = CRC_POLYLENGTH_7B;

  /* The default init value is used */
  CrcHandle.Init.DefaultInitValueUse     = DEFAULT_INIT_VALUE_ENABLE;

  /* The input data are not inverted */
  CrcHandle.Init.InputDataInversionMode  = CRC_INPUTDATA_INVERSION_NONE;

  /* The output data are not inverted */
  CrcHandle.Init.OutputDataInversionMode = CRC_OUTPUTDATA_INVERSION_DISABLE;

  /* The input data are bytes (8-bit long data) */
  CrcHandle.InputDataFormat              = CRC_INPUTDATA_FORMAT_BYTES;

  /* De-initialize the CRC peripheral */
  if (HAL_CRC_DeInit(&CrcHandle) != HAL_OK)
  {
    /* Initialization Error */
    Error_Handler();
  }  

  /* Then, initialize the CRC handle */
  if (HAL_CRC_Init(&CrcHandle) != HAL_OK)
  {
    /* Initialization Error */
    Error_Handler();
  }


  /****************************************************************************/
  /*                                                                          */
  /*         CRC computation of a first bytes stream                          */
  /*                                                                          */    
  /****************************************************************************/

  /* The 7-bit long CRC of a 5-byte buffer is computed. After peripheral initialization, 
     the CRC calculator is initialized with the default value that is 0x7F for 
     a 7-bit CRC.
    
    The computed CRC is stored in uint32_t uwCRCValue. The 7-bit long CRC is made of
    uwCRCValue 7 LSB bits. */

  uwCRCValue = HAL_CRC_Accumulate(&CrcHandle, (uint32_t *)&CRC7_DATA8_TEST5, BUFFER_SIZE_5);

  /* Compare the CRC value to the expected one */
  if (uwCRCValue != uwExpectedCRCValue_1)
  {
    /* Wrong CRC value: Turn LED3 on */
    Error_Handler();
  }

  
  /****************************************************************************/
  /*                                                                          */
  /*         CRC computation of a second bytes stream                         */
  /*                                                                          */    
  /****************************************************************************/

  /* The 7-bit long CRC of a 17-byte buffer is computed. The CRC calculator
    is not re-initialized, instead the previously computed CRC is used
    as initial value. */

  uwCRCValue = HAL_CRC_Accumulate(&CrcHandle, (uint32_t *)&CRC7_DATA8_TEST17, BUFFER_SIZE_17);

  /* Compare the CRC value to the expected one */
  if (uwCRCValue != uwExpectedCRCValue_2)
  {
    /* Wrong CRC value: Turn LED3 on */
    Error_Handler();
  }


  /****************************************************************************/
  /*                                                                          */
  /*         CRC computation of a single byte                                 */
  /*                                                                          */    
  /****************************************************************************/

  /* The 7-bit long CRC of a 1-byte buffer is computed. The CRC calculator
    is not re-initialized, instead the previously computed CRC is used
    as initial value. */

  uwCRCValue = HAL_CRC_Accumulate(&CrcHandle, (uint32_t *)&CRC7_DATA8_TEST1, BUFFER_SIZE_1);

  /* Compare the CRC value to the expected one */
  if (uwCRCValue != uwExpectedCRCValue_3)
  {
    /* Wrong CRC value: Turn LED3 on */
    Error_Handler();
  }


  /****************************************************************************/
  /*                                                                          */
  /*         CRC computation of the last bytes stream                         */
  /*                                                                          */    
  /****************************************************************************/

  /* The 7-bit long CRC of a 2-byte buffer is computed. The CRC calculator
    is re-initialized with the 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(). */

  uwCRCValue = HAL_CRC_Calculate(&CrcHandle, (uint32_t *)&CRC7_DATA8_TEST2, BUFFER_SIZE_2);

  /* Compare the CRC value to the expected one */
  if (uwCRCValue != uwExpectedCRCValue_4)
  {
    /* Wrong CRC value: Turn LED3 on */
    Error_Handler();
  }
  else
  {
    /* Right CRC value: Turn LED1 on */
    BSP_LED_On(LED1);
  }  


  /* Infinite loop */
  while (1)
  {
  }
}

多项式是0x65，没说初始值，有四组数据，

得到的CRC校验值分别为

uint32_t uwExpectedCRCValue_1 = 0x00000057;    /* First byte stream CRC  */

uint32_t uwExpectedCRCValue_2 = 0x0000006E;    /* Second byte stream CRC */

uint32_t uwExpectedCRCValue_3 = 0x0000004B;    /* Third byte stream CRC  */

uint32_t uwExpectedCRCValue_4 = 0x00000026;    /* Fourth byte stream CRC */

我不知道这个校验码是怎么得来的？网上下了好多CRC计算器，算的值都不对。

请问高手，谁知道是怎么计算的？谢谢！

Jacktang

那就奇怪了，好多CRC计算器算的值都不对

chenbingjy

Jacktang 发表于 2023-5-11 22:01 那就奇怪了，好多CRC计算器算的值都不对

是啊

huo_hu

硬件crc怎么设置多项式的值一直也没弄清楚

chenbingjy

huo_hu 发表于 2023-5-12 09:30 硬件crc怎么设置多项式的值一直也没弄清楚

这个多项式的值是0x65

chenbingjy

uint8_t crc7_mmc(uint8_t *data, uint16_t length)
{
    uint8_t i;
    uint8_t crc = 0x7f;        // Initial value
    while(length--)
    {
        crc ^= *data++;        // crc ^= *data; data++;
        for ( i = 0; i < 8; i++ )
        {
            if ( crc & 0x80 )
                crc = (crc << 1) ^ 0x65;        // 0x12 = 0x09<<(8-7)
            else
                crc <<= 1;
        }
    }
    return crc >> 1;
}

这是我的算法，可惜不对。不知道哪里出错了

chenbingjy

uint8_t checkCRC7(uint8_t *data, uint32_t len){
    uint8_t crc = 0xfe;
    uint8_t crcP = 0x65;
    uint8_t i, j;
    
    for ( i = 0; i < len; i++){
        crc ^= data[i];
        for (j = 0; j < 8; j++){
            if ( crc &0x80){
                crc ^= 0x65;
            }
            crc = crc <<1;
        }
    }	
    
	crc = crc >> 1;
    return crc;    
}
 

这个代码计算第一组和第四组数据都是对的

第二组和第三组不对

chenbingjy

uint32_t checkCRC71(uint8_t *data, uint32_t len){
    uint32_t crc = 0x000000fe;
    uint8_t crcP = 0x65;
    uint8_t i, j;
    
    for ( i = 0; i < len; i++){
        crc ^= (uint32_t)data[i];
        for (j = 0; j < 32; j++){
            if ( crc &0x80000000){
                crc ^= 0x65;
            }
            crc = crc <<1;
        }
    }	
    
	//crc = crc >> 1;
    return crc;    
}
 

我把代码改成这样只有第四组是对的