Can't seem to get correct results from CRC hardware

[JimFouch]

I have a routine that I have used for years on other processors and on PCs to get a CRC16 X-25 from a string. I'd like to get the hardware CRC to use the same CRC16.

I have tried every variant in the STM32CubeIDE and have not been able to get same output.

I know the X-25 uses an XOR of 0xFFFF which I do to the result I get from the HAL_CRC_Calculate.

I'm using my name as the test string...

unsigned char crcTest[]="Jim Fouch";

and then calling the CRC in HAL like this...

crcResult = ~HAL_CRC_Calculate(&hcrc, (uint32_t *)&crcTest, strlen(crcTest));

Here is my crc Init...

static void MX_CRC_Init(void)
{
 
  /* USER CODE BEGIN CRC_Init 0 */
 
  /* USER CODE END CRC_Init 0 */
 
  /* USER CODE BEGIN CRC_Init 1 */
 
  /* USER CODE END CRC_Init 1 */
  hcrc.Instance = CRC;
  hcrc.Init.DefaultPolynomialUse = DEFAULT_POLYNOMIAL_DISABLE;
  hcrc.Init.DefaultInitValueUse = DEFAULT_INIT_VALUE_DISABLE;
  hcrc.Init.GeneratingPolynomial = 4129;
  hcrc.Init.CRCLength = CRC_POLYLENGTH_16B;
  hcrc.Init.InitValue = 0xFFFF;
  hcrc.Init.InputDataInversionMode = CRC_INPUTDATA_INVERSION_NONE;
  hcrc.Init.OutputDataInversionMode = CRC_OUTPUTDATA_INVERSION_DISABLE;
  hcrc.InputDataFormat = CRC_INPUTDATA_FORMAT_BYTES;
  if (HAL_CRC_Init(&hcrc) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN CRC_Init 2 */
 
  /* USER CODE END CRC_Init 2 */
 
}

Which according to my coded routine and an online CRC test util, should return 0x0BAD. I know it's funny that my name returns "BAD" as a hex result. LOL

Here is the util I'm using... www.crccalc.com

Looking for any help. I'm sure I'm overlooking something.

[waclawek.jan]

Which STM32?

Drop Cube and feed the CRC byte-wise, as the first experiment, then try halfwords with various control bits settings.

JW

[JimFouch]

STM32H743

[JimFouch]

Figured it out.

Needed to Invert In & Out...

  hcrc.Instance = CRC;
  hcrc.Init.DefaultPolynomialUse = DEFAULT_POLYNOMIAL_DISABLE;
  hcrc.Init.DefaultInitValueUse = DEFAULT_INIT_VALUE_DISABLE;
  hcrc.Init.GeneratingPolynomial = 4129;
  hcrc.Init.CRCLength = CRC_POLYLENGTH_16B;
  hcrc.Init.InitValue = 0xFFFF;
  hcrc.Init.InputDataInversionMode = CRC_INPUTDATA_INVERSION_BYTE;
  hcrc.Init.OutputDataInversionMode = CRC_OUTPUTDATA_INVERSION_ENABLE;
  hcrc.InputDataFormat = CRC_INPUTDATA_FORMAT_BYTES;

and then invert the CRC

  crcResult = ~HAL_CRC_Calculate(&hcrc, (uint32_t *)&crcTest, strlen(crcTest));

[KConn.1]

Thank you for posting, have been struggling trying to get the HW crc calculator to produce the correct result and this got is working

This is what i needed for 16 bit CRC:

hcrc.Instance = CRC;
hcrc.Init.DefaultPolynomialUse = DEFAULT_POLYNOMIAL_DISABLE;
hcrc.Init.DefaultInitValueUse = DEFAULT_INIT_VALUE_DISABLE;
hcrc.Init.GeneratingPolynomial = 0x1021;
hcrc.Init.CRCLength = CRC_POLYLENGTH_16B;
hcrc.Init.InitValue = 0xFFFF;
hcrc.Init.InputDataInversionMode = CRC_INPUTDATA_INVERSION_HALFWORD;
hcrc.Init.OutputDataInversionMode = CRC_OUTPUTDATA_INVERSION_ENABLE;
hcrc.InputDataFormat = CRC_INPUTDATA_FORMAT_HALFWORDS;
 
if (HAL_CRC_Init(&hcrc) != HAL_OK)
{
    Error_Handler();
}

and in my case, no inversion needed on out put:

uint8_t data[] = {0, 1, 2, 3, 4, 5, 6, 7};
uint32_t hal_crc = HAL_CRC_Calculate(&hcrc, (uint32_t *)data, 4);

gets correct crc of 0x9DFD