CRC calculation in STM32G4

[sireevenkat1]

Hi,

I am working with STM32G491RE in my project. I have to transmit data through UART and I need to calculate CRC for that data.

in my application:

txdata[0] = 0x78;

txdata[1] = 0x04;

txdata[2] = 0x11;

txdata[3] = 0x01;

I have to calculate CRC16 for txdata[1] to txdata[3] and place it in txdata[4]& txdata[5].

1.I configured CRC parameters:

hcrc.Instance = CRC;

hcrc.Init.DefaultPolynomialUse = DEFAULT_POLYNOMIAL_ENABLE;

hcrc.Init.DefaultInitValueUse = DEFAULT_INIT_VALUE_ENABLE;

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();

}

2. I am using following function to calculate CRC

HAL_CRC_Calculate(&hcrc, (uint8_t *)txdata[1] ,3);
is it correct way to do or need to change anything.
Can anyone suggest.

Thanks

[Issamos]

Hello @sireevenkat1 

I suggest you to use this exemple.

Best regards.

II

[F.Belaid]

Hello @sireevenkat1,

HAL_CRC_Calculate() is used to compute the 7, 8, 16 or 32-bit CRC value of an 8, 16 or 32-bit data buffer independently of the previous CRC value. However, HAL_CRC_Accumulate() is being used depending on the combination of the previous CRC value and the new one in order to chain a CRC calculation. For further details check Using the CRC peripheral on STM32 microcontrollers - Application note.

I hope this help!

[sireevenkat1]

Hi @Issamos,

Thanks for the reply,

It will be helpful but my input data differs every time  based on the other peripheral output.
If I use below api

HAL_CRC_Accumulate(&hcrc, (uint32_t *)&CRC16_DATA8_CHECK, BUFFER_SIZE);
Is it possible to calculate CRC16 for txdata[1] to txdata[3] leaving txdata[0].
Thanks

[Tesla DeLorean]

You haven't defined the width of the polynomial, or it's value.

What would be helpful would be to cite what the receiving device is, and then a couple of known good test parameters to confirm its is working properly. There's a lot of critical parameters as they are very sensitive to bit ordering and sequencing.

[TDK · Accepted solution]

In additional to @Tesla DeLorean 's comments:

> HAL_CRC_Calculate(&hcrc, (uint8_t *)txdata[1] ,3);

You are missing a & sign. It should be this:

HAL_CRC_Calculate(&hcrc, (uint8_t *)&txdata[1], 3);

[sireevenkat1]

Hi @Tesla DeLorean, @TDK 

hcrc.Init.DefaultPolynomialUse = DEFAULT_POLYNOMIAL_ENABLE;

Is above statement don't make polynomial enable? Do I need to give value separately?

is below code correct way to do?

CRC_HandleTypeDef hcrc;

MX_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_ENABLE;

hcrc.Init.DefaultInitValueUse = DEFAULT_INIT_VALUE_ENABLE;

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 */

}

void function()

{

txdata[0] = 0x13;

txdata[1] = 0x04;

txdata[2] = 0x15;

txdata[3] = ACK;

// compute CRC to place into last 2 bytes

uint16_t calculatedCRC = HAL_CRC_Calculate(&hcrc,(uint32_t *)&txdata[1], 3);

txdata[4] = calculatedCRC & 0xFF; //low CRC byte

txdata[5] = (calculatedCRC >> 8& 0xFF; //high CRC byte

txdata[6] = 0x05;

HAL_UART_Transmit(&huart5, txdata,7, HAL_MAX_DELAY);

}

Thanks

[waclawek.jan]

@Tesla DeLoreansaid above:

> What would be helpful would be to cite what the receiving device is, and then a couple of known good test parameters to confirm its is working properly. There's a lot of critical parameters as they are very sensitive to bit ordering and sequencing.

JW

[Tesla DeLorean]

So it's using the default 32-bit polynomial?

If you're using you own protocol it would be sufficiently that both ends process the data consistently and generate the same check bytes for the same data.

[sireevenkat1]

Hi @Tesla DeLorean,

1.So it's using the default 32-bit polynomial?-------I think so, not sure.

I am using STM32G4 series .As per CRC application note below tables says polynomial coefficient is programmable. Based on what basis do I need to select polynomial coefficient can you suggest.

I saw some posts in forum they are using below polynomial. Can you suggest how do select value for  polynomial?

1.#define MODBUS_CRC_POLY 0x8005

2.#define MODBUS_CRC_POLY 0xA001

If I define my polynomial below configuration are sufficient?

hcrc.Init.GeneratingPolynomial = MODBUS_CRC_POLY;
hcrc.Init.CRCLength = CRC_POLYLENGTH_16B;
hcrc.Init.InitValue = 0xFFFF2.

3.My application is to send the data of  sensors and status of some sensors  to other module using UART. That module receives the data and send it to cloud.

Thanks