topic Re: Crc computation on K24 chip in Kinetis Microcontrollers

Crc computation on K24 chip

June — Thu, 01 Aug 2019 09:41:36 GMT

Hi,

I'm performing crc computation on K24 chip during run-time. As the address range to compute the crc is quite huge, it is broken up into several cycles. How to have the chip start a new calculation using an intermediate crc value from the previous calculation?

For example:

cycle 1: crc1 = Calculated crc from address 0x0001 to 0x0020

cycle 2: crc2 = calculated crc from crc1 and address 0x0021 to 0x0040

and so on...

How should crc1 be parsed in during cycle 2? As seed value or as a data?

Here's my code but it doesn't work:

<code>

static uint32_t Crc32(uint32_t const * const pData, uint32_t numLongs, uint32_t initCrc)

{

// Steps #1 and #2

CRC_CTRL = (CRC_CTRL_TOT(2U)) | // Input bits & bytes are transposed

(CRC_CTRL_TOTR(2U)) | // Output bits & bytes are transposed

(0UL << CRC_CTRL_WAS_SHIFT) | // Ready to write data

(1UL << CRC_CTRL_TCRC_SHIFT); // 32-bit CRC

// Step #3

CRC_GPOLY = 0x04C11DB7; // CRC32 polynomial

// Step #4 - Indicate seed will be written

CRC_CTRL = (CRC_CTRL_TOT(2U)) | // Input bits & bytes are transposed

(CRC_CTRL_TOTR(2U)) | // Output bits & bytes are transposed

(1UL << CRC_CTRL_WAS_SHIFT) | // Ready to write seed

(1UL << CRC_CTRL_TCRC_SHIFT); // 32-bit CRC

// Step #5 - Write seed

CRC_DATA = initCrc;

// Step #6 - Indicate that data follows

CRC_CTRL = (CRC_CTRL_TOT(2U)) | // Input bits & bytes are transposed

(CRC_CTRL_TOTR(2U)) | // Output bits & bytes are transposed

(0UL << CRC_CTRL_WAS_SHIFT) | // Ready to write data

(1UL << CRC_CTRL_TCRC_SHIFT); // 32-bit CRC

// Step #7 - Write the data values.

for (uint32_t i = 0; i < numLongs; i++)

{

CRC_DATA = pData[i];

}

// Step #8 - Return CRC result.

return CRC_DATA;

}

// Note: the following is a pseudo code just to illustrate the logic

// The following doesn't work. What's wrong?

main()

{

while (!crcDone)

{

readData(&data[0]);

if (cycle1)

{

crc = crc32(data[0], numBytes, 0xFFFFFFFFUL);

}

else

{

crc = crc32(data[0], numBytes, crc);

}

CompareCrcWithStoredCrc();

}

// I have also tried the following but it doesn't work either:

main()

{

while (!crcDone)

{

readData(&data[4]);

if (cycle1)

{

crc = crc32(data[4], numBytes, 0x0UL);

}

else

{

memcpy(&data[0], &crc, 4);

crc = crc32(data[0], numBytes+4, 0x0UL);

}

CompareCrcWithStoredCrc();

}

<code>

Appreciate some advice. Thanks!

Re: Crc computation on K24 chip

Alexis_A — Thu, 01 Aug 2019 20:07:09 GMT

Hi,

Comparing your code with the SDK example I see that your missing the clock enable for the CRC module.

I will suggest to check the example code that is in the MK24 SDK. You can download it from here:

https://mcuxpresso.nxp.com/

Let me know if this helps you.

Best Regards,

Alexis Andalon

Re: Crc computation on K24 chip

June — Fri, 02 Aug 2019 05:50:39 GMT

Hi Alexis,

The SCGC clock for CRC is already enabled in the startup code and i have checked that it is set for crc. So unfortunately it doesn't help. Thanks.

I'm curious to know if anyone has had any success using the crc this way?

Re: Crc computation on K24 chip

Alexis_A — Tue, 06 Aug 2019 00:14:27 GMT

Hi YiJun,

I found something strange in the previous code.

The function static uint32_t Crc32(uint32_t const * const pData, uint32_t numLongs, uint32_t initCrc) receive a pointer for the data but when you call the function you only use the value from the array data[0] or data[4]. I think if you store the data in the array you should pass the direction from the first pointer (data or &data[0]).

Also, I will suggest to test the SDK example, maybe you could base your application in this one.

Let me know if this helps you.

Best Regards,

Alexis Andalon