CRC calculation in software

[drechsel]

Posted on September 05, 2009 at 14:24

CRC calculation in software

[Shang.Dawei]

Posted on May 17, 2011 at 13:17

[DEAD LINK /public/STe2ecommunities/mcu/Lists/ARM%20CortexM3%20STM32/Flat.aspx?RootFolder=/public/STe2ecommunities/mcu/Lists/ARM CortexM3 STM32/CRC32 calculation mismatch&FolderCTID=0x01200200770978C69A1141439FE559EB459D758000626BE2B829C32145B9EB5739142DC17E&currentviews=635]https://my.st.com/public/STe2ecommunities/mcu/Lists/ARM%20CortexM3%20STM32/Flat.aspx?RootFolder=/public/STe2ecommunities/mcu/Lists/ARM%20CortexM3%20STM32/CRC32%20calculation%20mismatch&FolderCTID=0x01200200770978C69A1141439FE559EB459D758000626BE2B829C32145B9EB5739142DC17E&currentviews=635

//****************************************************************************

DWORD CRC32WideFast(DWORD Crc, DWORD Size, BYTE *Buffer)

{

Size = Size >> 2; // /4

while(Size--)

{

static const DWORD CrcTable[16] = { // Nibble lookup table for 0x04C11DB7 polynomial

0x00000000,0x04C11DB7,0x09823B6E,0x0D4326D9,0x130476DC,0x17C56B6B,0x1A864DB2,0x1E475005,

0x2608EDB8,0x22C9F00F,0x2F8AD6D6,0x2B4BCB61,0x350C9B64,0x31CD86D3,0x3C8EA00A,0x384FBDBD };

Crc = Crc ^ *((DWORD *)Buffer); // Apply all 32-bits

Buffer += 4;

// Process 32-bits, 4 at a time, or 8 rounds

Crc = (Crc << 4) ^ CrcTable[Crc >> 28]; // Assumes 32-bit reg, masking index to 4-bits

Crc = (Crc << 4) ^ CrcTable[Crc >> 28]; //  0x04C11DB7 Polynomial used in STM32

Crc = (Crc << 4) ^ CrcTable[Crc >> 28];

Crc = (Crc << 4) ^ CrcTable[Crc >> 28];

Crc = (Crc << 4) ^ CrcTable[Crc >> 28];

Crc = (Crc << 4) ^ CrcTable[Crc >> 28];

Crc = (Crc << 4) ^ CrcTable[Crc >> 28];

Crc = (Crc << 4) ^ CrcTable[Crc >> 28];

}

return(Crc);

}

[petter23]

Posted on October 11, 2011 at 14:53

I got this code to produce what seems to be CRC-32 on even 4-byte input using the CRC unit correctly, at least it produces the same CRC-32 as perl crc32 and some other CRC-32 according to the mentioned specifikation earler.

#include ''stm32f2xx.h''

uint32_t my_crc32(uint8_t* data, uint32_t len)

{

    uint32_t* pBuffer = (uint32_t*) data;

    uint32_t BufferLength = len/4;

    uint32_t index = 0;

    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_CRC, ENABLE);

    CRC_ResetDR();

      

    for(index = 0; index < BufferLength; index++)

    {

        CRC->DR = __RBIT(pBuffer[index]);

    }

    return __RBIT(CRC->DR) ^ 0xFFFFFFFF;

}

[Tesla DeLorean]

Posted on October 11, 2011 at 15:37

There have been quite a few discussions on CRC computation, including this one which adapts mcuisp's 32-bit algorithm to byte boundary conditions.

[DEAD LINK /public/STe2ecommunities/mcu/Lists/cortex_mx_stm32/Flat.aspx?RootFolder=/public/STe2ecommunities/mcu/Lists/cortex_mx_stm32/CRC computation&FolderCTID=0x01200200770978C69A1141439FE559EB459D7580009C4E14902C3CDE46A77F0FFD06506F5B&currentviews=1034]CRC Computation

Unfortunately most of the pre May-2011 links are broken due to forum software failures.

[Tesla DeLorean]

Posted on February 03, 2018 at 17:03

Current working link

https://community.st.com/0D50X00009XkbNMSAZ

 

[rdittmar]

Posted on March 29, 2012 at 16:45

Hey swhite!

Perfect - thank you - that helped me a lot!!!