On 08/13/2010 08:55 AM, Heinz-Jürgen Oertel wrote: > Am Mittwoch, 11. August 2010 17:59:17 schrieb Marc Kleine-Budde: >> Bit timing parameters for flexcan with 24.576000 MHz ref clock >> nominal real Bitrt nom real SampP >> Bitrate TQ[ns] PrS PhS1 PhS2 SJW BRP Bitrate Error SampP SampP >> Error CAN_CTRL 1000000 40 8 8 8 1 1 983040 1.7% 75.0% >> 68.0% 9.3% 0x003f0007 1000000 81 4 4 3 1 2 1024000 2.4% >> 75.0% 75.0% 0.0% 0x011a0003 1000000 122 2 3 2 1 3 >> 1024000 2.4% 75.0% 75.0% 0.0% 0x02110001 >> > > > Hello Wolfgang, Marc, > I was not aware that the clock is 24.576000 MHz, always thought 24.000000. > It is often the case that the crystal clock is chosen to get a perfect bit > rate for UARTS, not for CAN. But a UART frame, having only 10 bits, can live > with a much higher deviation from the nominal bit clock.
Yep, a good CAN clock has a frequency of (n * 8) MHz. > I see that you typical use a sample point at 75%. > CANopen has a "Recommended location of sample point" at 87.5%. (CiA 301). But not at 1 MHz!? We use: http://lxr.linux.no/#linux+v2.6.35/drivers/net/can/dev.c#L82 Please correct me if I'm wrong. Wolfgang. _______________________________________________ Socketcan-users mailing list [email protected] https://lists.berlios.de/mailman/listinfo/socketcan-users
