From: Wolfgang Grandegger <wg-5Yr1BZd7O62+XT7JhA+gdA@public•gmane.org>
To: Pavel Pisa <pisa-/N2ztlQkxE7Ub/6JBqosbQ@public•gmane.org>
Cc: SocketCAN Core Mailing List
<socketcan-core-0fE9KPoRgkgATYTw5x5z8w@public•gmane.org>,
Oliver Hartkopp
<socketcan-fJ+pQTUTwRTk1uMJSBkQmQ@public•gmane.org>,
Linux Netdev List
<netdev-u79uwXL29TY76Z2rM5mHXA@public•gmane.org>
Subject: Re: [PATCH net-next v2] candev: allow SJW user setting for bittiming calculation
Date: Sat, 24 Sep 2011 09:44:15 +0200 [thread overview]
Message-ID: <4E7D8A4F.7010806@grandegger.com> (raw)
In-Reply-To: <201109231132.49976.pisa-/N2ztlQkxE7Ub/6JBqosbQ@public.gmane.org>
Hi Pavel,
On 09/23/2011 11:32 AM, Pavel Pisa wrote:
> Hello Oliver and Wolfgang,
...
> I hope that actual calculation works reasonably well.
> But if it should be enhanced, then it would worth
> to add additional parameter except crystal/controller
> clock source freqency to the concrete boards drivers.
> It should be measured round-trip delay of given/used
> transceiver/optocouplers combination. This would
> allow to have sampling point setup yet more independent
> on given HW and same value could be used for different
> bitrates. But there is still unknown parameter
> capacity/length of connected wires so there is still
> something left to user consideration.
The actual in-kernel bit-timing calculation is known to work well for
most, not all, CAN users, especially with "good" clock source
frequencies (a multiple of 8 MHz). That's fine and intended. The results
of that algorithm are not always satisfactory. Such cases should then be
handled in user-space, either manually or by an advanced algorithm. In
the BerliOS "can-utils" there we have already "can-calc-bit-timing". Any
enhancements and improvements would be nice to share, indeed. Do you
already have/use some code for the enhancement mentioned above?
Wolfgang.
next prev parent reply other threads:[~2011-09-24 7:44 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-22 10:28 [PATCH net-next v2] candev: allow SJW user setting for bittiming calculation Oliver Hartkopp
[not found] ` <4E7B0DE6.9020807-fJ+pQTUTwRTk1uMJSBkQmQ@public.gmane.org>
2011-09-22 13:07 ` Wolfgang Grandegger
[not found] ` <4E7B331F.3070801-5Yr1BZd7O62+XT7JhA+gdA@public.gmane.org>
2011-09-22 16:26 ` Oliver Hartkopp
[not found] ` <4E7B61C8.8020506-fJ+pQTUTwRTk1uMJSBkQmQ@public.gmane.org>
2011-09-22 18:10 ` Wolfgang Grandegger
[not found] ` <4E7B7A30.4030707-5Yr1BZd7O62+XT7JhA+gdA@public.gmane.org>
2011-09-22 19:41 ` Oliver Hartkopp
[not found] ` <4E7B8F63.6060108-fJ+pQTUTwRTk1uMJSBkQmQ@public.gmane.org>
2011-09-23 7:24 ` Wolfgang Grandegger
[not found] ` <4E7C3424.8030406-5Yr1BZd7O62+XT7JhA+gdA@public.gmane.org>
2011-09-23 9:32 ` Pavel Pisa
[not found] ` <201109231132.49976.pisa-/N2ztlQkxE7Ub/6JBqosbQ@public.gmane.org>
2011-09-23 15:50 ` Oliver Hartkopp
2011-09-24 7:22 ` Wolfgang Grandegger
[not found] ` <4E7D8537.8010302-5Yr1BZd7O62+XT7JhA+gdA@public.gmane.org>
2011-09-27 17:32 ` Oliver Hartkopp
[not found] ` <4E8208B5.4050907-fJ+pQTUTwRTk1uMJSBkQmQ@public.gmane.org>
2011-09-27 20:04 ` Wolfgang Grandegger
2011-09-24 7:44 ` Wolfgang Grandegger [this message]
2011-09-27 20:05 ` Wolfgang Grandegger
2011-09-29 6:14 ` Kurt Van Dijck
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