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Date: Sat, 24 Sep 2011 09:44:15 +0200 From: Wolfgang Grandegger <wg@...ndegger.com> To: Pavel Pisa <pisa@....felk.cvut.cz> CC: SocketCAN Core Mailing List <socketcan-core@...ts.berlios.de>, Oliver Hartkopp <socketcan@...tkopp.net>, Linux Netdev List <netdev@...r.kernel.org> Subject: Re: [PATCH net-next v2] candev: allow SJW user setting for bittiming calculation 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. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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