Re: How CRC for CAN bus is calculated

That's correct, the CAN controller normally does this calculation 
automatically, so it's generally not necessary to do it in software.  I 
had written this in the past when I was analyzing the low level details 
of a CAN interface and wanted to validate the CRC.

S

On 01/09/2014 01:39 AM, Dinesh Guleria wrote:
> @steve
>
> Your code seems to be CRC-16 ?
>
> >> Here's some example C code that calculates the CRC for a CAN message.
> Does CAN controller does not do the CRC calculation of data message on 
> its own ?
>
> Regards,
> Dinesh
>
>
> On Wed, Jan 8, 2014 at 6:52 PM, Stephen Glow 
> <[email protected] 
> <mailto:[email protected]>> wrote:
>
>     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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