Hello, I’m facing some problems with the CRC HAL library when I want to change the polynomial to use. I want to use the 16 bits CRC/ARC polynomial (0x8005).

[MDura.9]

I try this to use this:

/* Private function prototypes -----------------------------------------------*/

void SystemClock_Config(void);

uint32_t CRCtest0 = 0;

uint32_t CRCtest1 = 0;

//uint32_t CRCtest2 = 0;

uint8_t txData[10]={0xF2, 0x10, 0x10, 0xE0, 0x3F, 0x35};

uint8_t crcdatatest1 [4] = {0xF2, 0x10, 0x10, 0xE0};

uint8_t crcdatatest2 [4] = {0xE0, 0x10, 0x10, 0xF2};

int main(void)

{

 /* MCU Configuration----------------------------------------------------------*/

 HAL_Init();                        

 SystemClock_Config();   

 /* Initialize all configured peripherals */

 MX_GPIO_Init();

 MX_DMA_Init();

 MX_USART2_UART_Init();

 MX_ADC1_Init();

 MX_CAN1_Init();

 MX_COMP1_Init();

 MX_COMP2_Init();

 MX_CRC_Init();

 MX_UART4_Init();

 MX_UART5_Init();

 MX_SPI2_Init();

 MX_I2C1_Init();

HAL_CRCEx_Polynomial_Set(&hcrc, 0x8005, CRC_POLYLENGTH_16B);

hcrc.Init.DefaultInitValueUse = 0;

hcrc.Init.InitValue = 0;

 /* Infinite loop */

 while (1)

 {

CRCtest0 = HAL_CRC_Calculate(&hcrc, (uint32_t *)txData, 4);

   CRCtest1 = HAL_CRC_Calculate(&hcrc, (uint32_t *)crcdatatest1, 4);

   HAL_Delay(1000);

 }

}

The returned values in CRCtest0 and CRCtest2 are both 0x8B0C which is not correct. According to CRC16/ARC polynomial the result should by 0x353F.

There is any other configuration that I’m missing?

Thanks,

Manel

[Tesla DeLorean]

>>There is any other configuration that I’m missing?

Don't know, you don't really show any configuration. The bit/byte ordering and shift direction will be critical.

[Tesla DeLorean]

Well I can understand where the 0x0C8B might come from. I can get to 0x353F with this

uint16_t Crc16Slow(uint16_t Crc, int Size, uint8_t *Buffer)
{
 int i;
 
 while(Size--)
 {
 Crc ^= *Buffer++; // Apply Data
 for (i=0; i<8; i++) // 1-bit at a time
 if (Crc & 0x0001)
 Crc = (Crc >> 1) ^ 0xA001; // 0x8005 Polynomial used in ARC Reversed
 else
 Crc = (Crc >> 1);
 }
 
 return(Crc);
}

[Tesla DeLorean]

//****************************************************************************
 
/**
 * @brief This function configures CRC Instance.
 * @note This function is used to :
 * -1- Enable peripheral clock for CRC.
 * -2- Configure CRC functional parameters.
 * @note Peripheral configuration is minimal configuration from reset values.
 * Thus, some useless LL unitary functions calls below are provided as
 * commented examples - setting is default configuration from reset.
 * @param None
 * @retval None
 */
void Configure_CRC(void)
{
 /* (1) Enable peripheral clock for CRC *********************/
 LL_AHB1_GRP1_EnableClock(LL_AHB1_GRP1_PERIPH_CRC);
 
 /* (2) Configure CRC functional parameters ********************************/
 
 /* Configure CRC calculation unit with user defined polynomial value, 16-bit long */
 LL_CRC_SetPolynomialCoef(CRC, 0x8005);
 LL_CRC_SetPolynomialSize(CRC, LL_CRC_POLYLENGTH_16B);
 LL_CRC_SetInitialData(CRC, 0);
 LL_CRC_SetInputDataReverseMode(CRC, LL_CRC_INDATA_REVERSE_BYTE);
 LL_CRC_SetOutputDataReverseMode(CRC, LL_CRC_OUTDATA_REVERSE_BIT);
}
 
//****************************************************************************