On Tuesday, February 08, 2011 12:53 AM, Wolfgang Grandegger wrote: > BTW, it's always possible to specify optimized bit-timing > parameters directly, e.g. the following seem better: > > 800000 60 12 4 4 4 3 793650 0.8% 80.0% 81.0% 1.2% > > You could set these with: > > $ ip link set can0 type can \ > tq 60 prop-seg 12 phase-seg1 4 phase-seg2 4 sjw 4
I can confirm 800K comms works well using the above. I wish Can-core could calculate like above. >> seg1/seg2/sjw/prop_seg must be more than 1 ? BTW, according to EG20T PCH data sheet, CAN bit-timing parameters(BRP, Prop_Seg, Phase_Seg1, Phase_Seg2, SJW) must not be set 0. Thanks, ----------------------------------------- Tomoya MORINAGA OKI SEMICONDUCTOR CO., LTD. > -----Original Message----- > From: Wolfgang Grandegger [mailto:[email protected]] > Sent: Tuesday, February 08, 2011 12:53 AM > To: Tomoya MORINAGA > Cc: [email protected]; [email protected]; > [email protected] > Subject: Re: About bittiming calculation result > > On 02/07/2011 01:00 PM, Wolfgang Grandegger wrote: > > Hi Tomoya, > > > > On 02/07/2011 12:38 PM, Tomoya MORINAGA wrote: > >> Hi, > >> > >> I have a question for bittiming-value calculated by Can-core. > >> > >> In case setting like below, > >> - ip link set can0 type can bitrate 800000 > >> - clock=50MHz > >> - Use pch_can > >> > >> Can-core calculates like below > >> brp=21 > >> seg1=1 > >> seg2=1 > >> sjw=1 > >> prop_seg=0 > >> > >> Is "prop_seg=0" true ? > > > > Well, only prop_seg+phase_seg=tseg1 is relevant and the > pch_can driver > > sets the allowed minimum "tseg1_min1" currently to 1: > > > > static struct can_bittiming_const pch_can_bittiming_const = { > > .name = KBUILD_MODNAME, > > .tseg1_min = 1, > > .tseg1_max = 16, > > .tseg2_min = 1, > > .tseg2_max = 8, > > .sjw_max = 4, > > .brp_min = 1, > > .brp_max = 1024, /* 6bit + extended 4bit */ > > .brp_inc = 1, > > }; > > > >> seg1/seg2/sjw/prop_seg must be more than 1 ? > > > > Then "tseg1_min" should be set to *2*. > > > >> Also I can see the following kernel error log. > >> bitrate error 0.7% > > > > A clock frequency of 50 MHz is sub-optimal for CAN and some > bit-rates > > cannot be reproduced properly. Here is the output of the can-utils > > program "can-calc-bit-timing" (with an entry for the pch-can added): > > > > $ ./can-calc-bit-timing pch-can > > Bit timing parameters for pch-can with 50.000000 MHz ref clock > > nominal real Bitrt nom real SampP > > Bitrate TQ[ns] PrS PhS1 PhS2 SJW BRP Bitrate Error SampP > SampP Error CNF1 CNF2 CNF3 > > 1000000 100 3 3 3 1 5 1000000 0.0% 75.0% > 70.0% 6.7% 0x05 0x92 0x02 > > 800000 420 0 1 1 1 21 793650 0.8% 80.0% > 66.6% 16.8% 0x15 0xff 0x00 > > 500000 100 8 8 3 1 5 500000 0.0% 87.5% > 85.0% 2.9% 0x05 0xbf 0x02 > > 250000 500 3 3 1 1 25 250000 0.0% 87.5% > 87.5% 0.0% 0x19 0x92 0x00 > > 125000 500 6 7 2 1 25 125000 0.0% 87.5% > 87.5% 0.0% 0x19 0xb5 0x01 > > 100000 500 8 8 3 1 25 100000 0.0% 87.5% > 85.0% 2.9% 0x19 0xbf 0x02 > > 50000 2500 3 3 1 1 125 50000 0.0% 87.5% > 87.5% 0.0% 0x7d 0x92 0x00 > > 20000 2500 8 8 3 1 125 20000 0.0% 87.5% > 85.0% 2.9% 0x7d 0xbf 0x02 > > 10000 12500 3 3 1 1 625 10000 0.0% 87.5% > 87.5% 0.0% 0x71 0x92 0x00 > > > > As you can see, especially 800000 gives rather bad results. > > BTW, it's always possible to specify optimized bit-timing > parameters directly, e.g. the following seem better: > > 800000 60 12 4 4 4 3 793650 0.8% 80.0% 81.0% 1.2% > > You could set these with: > > $ ip link set can0 type can \ > tq 60 prop-seg 12 phase-seg1 4 phase-seg2 4 sjw 4 > > Wolfgang. > _______________________________________________ Socketcan-core mailing list [email protected] https://lists.berlios.de/mailman/listinfo/socketcan-core
