On 08/11/2010 08:13 PM, Wolfgang Grandegger wrote: > On 08/11/2010 05:59 PM, Marc Kleine-Budde wrote: >> Wolfgang Grandegger wrote: >> [...] >> >>>>> However the mainline driver only supports the bus clock. >>>> and with this clock, if it is 66.5 MHz, one Mbit/s can not be reached. >>> >>> OK. Another problem might be that 66.5 MHz does not give *good* >>> bit-timing parameters as confirmed by my can-calc-bit-timing: >>> >>> $ ./can-calc-bit-timing -c 66500000 flexcan >>> Bit timing parameters for flexcan using 66500000Hz >>> Bitrate TQ[ns] PrS PhS1 PhS2 SJW BRP SampP Error >>> 1000000 90 4 3 3 1 6 72.7% 0.8% !! >>> 800000 180 2 2 2 1 12 71.4% 1.0% >>> 500000 105 8 7 3 1 7 84.2% 0.0% >>> 250000 285 8 3 2 1 19 85.7% 0.0% >>> 125000 571 8 3 2 1 38 85.7% 0.0% >>> 100000 526 8 7 3 1 35 84.2% 0.0% >>> 50000 1428 8 3 2 1 95 85.7% 0.0% >>> 20000 2631 8 7 3 1 175 84.2% 0.0% >>> >>> It it's even worse with worse with 24.576MHz: >>> >>> $ ./can-calc-bit-timing -c 24576000 flexcan >>> Bit timing parameters for flexcan using 24576000Hz >>> Bitrate TQ[ns] PrS PhS1 PhS2 SJW BRP SampP Error >>> 1000000 40 8 8 8 1 1 68.0% 1.7% !!!! >>> 800000 122 5 2 2 1 3 80.0% 2.4% >>> 500000 284 2 2 2 1 7 71.4% 0.3% >>> 250000 569 2 2 2 1 14 71.4% 0.3% >>> 125000 1139 2 2 2 1 28 71.4% 0.3% >>> 100000 1424 2 2 2 1 35 71.4% 0.3% >>> 50000 1668 7 2 2 1 41 83.3% 0.1% >>> 20000 5004 5 2 2 1 123 80.0% 0.1% >>> 10000 7690 8 2 2 1 189 84.6% 0.0% >>> >>> Marc, what's happened with your optimized version of >>> can-calc-bit-timing? Does it find better values? >> >> I just noticed that the can-calc-bit-timing is in can-test and an >> improved version is in can-utils. I commited the improved version to >> can-utils, but shame on me, 2 month after you've commited the initial >> version to can-test. What should we do? > > I have not committed any version of can-calc-bit-timing. I did not see > your version due to some svn update problems. Sorry for the noise. > >> However, the improved algorithm may just find better (i.e. lesser) >> sample point errors but the bit rate error stays the same. > > The improved algorithm is not what exactly what we have in the kernel, > right? Anyway, the algorithm will not make anybody happy.
s/anybody/everybody/ Wolfgang. _______________________________________________ Socketcan-users mailing list [email protected] https://lists.berlios.de/mailman/listinfo/socketcan-users
