Re: How CRC for CAN bus is calculated

Here's some example C code that calculates the CRC for a CAN message.

Rgds,
Steve

static uint16_t CRC_AddBits( uint16_t crc, uint16_t value, int bct )
{
    uint16_t mask = 1<<(bct-1);
    while( mask )
    {
       int bit = (value&mask) ? 1 : 0;
       if( crc & 0x4000 )
      bit = !bit;
       crc <<= 1;
       if( bit ) crc ^= 0x4599;
       mask>>=1;
    }

    return crc & 0x7FFF;
}

static uint16_t CalcCRC( int id, int ct, uint8_t data[] )
{
    uint16_t crc = 0;
    int i;

    // Add start of frame and ID
    crc = CRC_AddBits( crc, id&0x7FF, 12 );

    // Add RTR, IDE, r1 and count
    crc = CRC_AddBits( crc, ct&0x0F, 7 );

    if( ct > 8 ) ct = 8;

    for( i=0; i<ct; i++ )
       crc = CRC_AddBits( crc, data[i], 8 );

    return crc;
}


On 01/08/2014 08:03 AM, yogesh zambare wrote:
> Dear All,
> Can anybody tell me how CRC for CAN bus is calculated?
>
> Regards,
> Yogesh Zambare
> --
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