Re: Problem of accuracy

[Oliver Hartkopp <oliver.hartkopp@volkswagen.de>]

On 05.07.2012 10:12, Mohamed HAMZAOUI wrote:
> Hi,
>
> i'm a new user of socketcan and, i cross compile can-utils for my craneboard
> card (a card with CAN).
> When i run cangen with 1 ms period, the period is not respected (1,407, 1.399,
> ...) !
>
> How can i fix this problem ?
>
> my can version in /proc/net/can/version is "rev 20090105 abi 8" and i'm on
> : Linux am3517-crane 2.6.32 #1 Mon Apr 23 00:13:28 CEST 2012 armv7l GNU/Linux
>

Hello Mohamed,

first please move to the new CAN mailing list (see CC) - and don't use 
HTML-mails (text-only is better) ;-)

Regarding your problem:

Usually i get smaller derivations on my system - but your Linux box is 
probably not very fast, so that you can see these scheduling influences with 
cangen ...

cangen is a userpace app and therefore it is usually not that precise as 
hrtimers inside the Linux kernel (if you don't use any realtime Linux).

But you may try the Broadcast-Manager to place a 'cyclic sending job' inside 
the Linux kernel. See an example here:

http://svn.berlios.de/wsvn/socketcan/trunk/test/tst-bcm-cycle.c

Regards,
Oliver